Download Final Review Report - Cardiff Physics and Astronomy

Photon-Mediated Phenomena in Semiconductor Nanostructures
(Photon-Mediated Phenomena, HPRN-CT-2002-00298)
Start date: August 01, 2002
Duration: 48 months
Final Report
(August 01, 2005 – July 31, 2006)
Network co-ordinator: Prof Alex L. Ivanov
School of Physics and Astronomy
Cardiff University
Queens Buildings
The Parade
Cardiff CF24 3AA
Wales, United Kingdom
Tel: +44 - 2920 - 875315
Fax: +44 – 2920 – 874056
Email: [email protected]
Network home page: http://www.astro.cardiff.ac.uk/research/PMPnetwork/index.html
PART A - RESEARCH RESULTS
A.1 Scientific Highlights
We have followed the main scientific aims formulated in our Network project.
Task 1. Optics of QDs embedded in a three-dimensional microcavity
(Lead team: Dortmund)
The experiments performed by the Network YR, Dr N. Le Thomas (Dortmund team),
demonstrated the highest coupling efficiency of spontaneous emission (beta-factor) ever
observed for semiconductor nanocrystals. This result was achieved by replacing spherical,
colloidal CdSe nanocrystals by anisotropic CdSe nanorods. The highly polarized emission
couples almost 100% into TE-modes of spherical microcavities while the TM-modes are
suppressed. Dr N. Le Thomas also achieved an optical detection of single CdSe nanorods and
analysed the temperature-dependent line shape.
Strong coupling of atoms or semiconductor quantum dots with photons in high-Q
microsphere cavities are in the focus of current investigations. Such systems are discussed e.g.
as sources of deterministic single photons and entangled photons. Semiconductor
nanocrystals, as has been demonstrated in antibunching experiments are possible candidates of
a solid state-based “atom”, however, their optical transition dipole moment was found to be
much smaller with respect to epitaxially grown quantum dots. We studied the impact of
anisotropy and crystal symmetry of semiconductor nanostructures for achieving high optical
transition dipole moments by comparing nanorods and nanodots. Making use of the Bloch
part of the excitonic wave function, i.e. the solid state nature of the “artificial atom”, we are
able to transform the exciton ground state symmetry of a CdSe nanorod from an optically dark
to optically bright states with high degree of linear polarisation. By measuring the photon
lifetime, we show experimentally for R = 3µm spheres with a sufficiently low mode volume V
~ 200(/n)3, the existence of a high quality factor Q > 200 000, which should be allow to
enter the strong coupling regime with emitters of ~3ns-1 spontaneous radiative decay rate. By
attaching the spheres with nanocrystals having a high optical transition dipole moment, the
line shape of some cavity modes exhibit a splitting of ~40 µeV that we attributed to the strong
coupling regime.
The Network YR, Dr N. Le Thomas, has completed his stay in Dortmund and went to the
EPFL Lausanne to join the group of R. Houdre. During the last period of his work within the
project he has completed the study of the impact of anisotropy and crystal symmetry of
semiconductor nanostructures for achieving high optical transition dipole moments by
comparing nanorods and nanodots. He has analysed the effect of exchange interaction on
CdSe nanorods and expanded his studies to CdTe nanocrystals, a material which is promising
for NIR applications and functionalization of photonic bandgap materials. Making use of the
higher optical transition dipole moment of CdSe nanorods, the strong coupling regime is now
demonstrated for a strongly coupled cavity QED system consisting of a CdSe nanocrystal
coupled to a single photon mode of a polymer microsphere. The strong exciton-photon
coupling is manifested by the observation of a cavity mode splitting of 35 to 45 µeV and
lifetime measurements of the coupled exciton-photon state. The single photon mode is
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isolated by lifting the mode degeneracy in a slightly deformed microsphere and addressing it
by high-resolution imaging spectroscopy. This cavity mode is coupled to a localized exciton
of an anisotropically shaped CdSe nanocrystal on the microsphere surface that emits highly
polarized light in resonance to the mode.
In the final period of the Network project Dr. Marco Allione joined as postdoctoral
researcher the Dortmund group to complete the project on single nanorod spectroscopy. As a
new topic he started studies towards plasmonic nanocavities consisting of metallic nanowires
with/without nanocrystal quantum dots as active optical medium. His research was part of a
larger study on quantum optical properties of solid-state microcavities in the so-called “badcavity limit” in our group to which Dr. Vasily Temnov, Dr. Yuri Fedutik and Dipl. Phys.
Oliver Schöps contributed. A first result is a theoretical work about superradiance and
subradiance within an inhomogeneous ensemble of quantum dots in optical microcavities. The
YR Marco Allione contributed with first results about confined plasmons in silver nanowires.
He also has completed together with Nicolas LeThomas the study of charged excitons in CdSe
nanorods (manuscript is in preparation).
After his leaving to EPFL Lausanne, an intense research collaboration has established with
the Dortmund group and the former YR Nicolas LeThomas. He was involved in the further
training of Marco Allione and contributed further to the work on CdTe nanocrystals with an
analysis of the effect of exchange interaction. He also presented the results about the strongcoupling regime of CdSe nanorods in microspheres at several conferences on behalf of the RT
network. In addition he completed his calculations and experiments on whispering gallery
mode sensors which is accepted for publications in JOSA B.
The Dortmund team received additional funds from an intern network transfer and could
offer three-person-month to a PhD-student. These funds have been allocated to Jordi Gomes
from Spain who worked in Dortmund from May 1 until July 31. In these three month Jordi
Gomes was trained in different techniques of ultrafast spectroscopy and took part on
experiments to study quantum dot dynamics.
Within “Dortmund-Paderborn” cooperation, in order to develop tuneable, photochemically
stable, and positioned nanoemitters in photonic structures we tested a new epitaxial technique,
the hybrid growth of MBE using nanocrystals as colloidal seeds. The enormous potential of
colloidal nanocrystals concerning tunability shall be combined with device-compatible
techniques of Molecular Beam Epitaxy to grow monolithic, high-Q optical microcavities with
nanocrystals as the active optical material. It is planned to test different nanocrystalline
emitters by integrating them in compact, monolithic microcavities or by embedding them in
micromechanically tuned microcavities with movable 2D-structured mirrors as an alternative
approach. The optical properties we want to control are the positioning of nano-emitters in
field maxima/minima, stable single dot emission, control of polarization degree, minimizing
of decoherence, and transition dipole moment control by wave function engineering. A result
of the above cooperation is a joint Dortmund/Paderborn patent application. Later on, the
hybrid growth of MBE using nanocrystals as colloidal seeds has been further developed. The
work has been focussed on the control of nanocrystal concentration and wetting of the organic
solution. To measure the concentration of the optical active nanocrystals, the Dortmudn group
has built-up a set-up to monitor blinking phenomena for different deposition techniques. The
patent application has been expanded to Europe and US. Finally, the new epitaxial technique,
the hybrid growth of MBE using nanocrystals as colloidal seeds, has been further developed.
The nanocrystal concentration and wetting of the organic solution on a ZnSe substrate can
now be controlled. In close cooperation with the group of Detlef Schikora, Oliver Schöps
from the Dortmund group has measured concentration of the optical active nanocrystals and
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monitored blinking phenomena before and after overgrowth. The results have been
successfully presented at conferences and a publication is in preparation.
The Network YR, Dr N. Nikolaev (Cardiff team) developed theoretical optics of single
photonic dots, and these theoretical results have been shared with the Dortmund and Lund
teams. The Grenoble team, involving support from other national grants, has received a
progress in fabrication of solid state single photon sources based on CdTe and CdSe quantum
dots in pillar microcavities. An experimental set-up has been developed for quantum optics
measurements of these photonic devices at low temperature (photon correlation,
entanglement, interference with two photons, etc.). This acquired knowledge was shared with
the Network partners. Close collaboration was with the Cardiff team to which the former
members of the Dortmund team W. Langbein and P. Borri moved in 2004, and B. Patton in
2005. A joint project about FWM at single quantum dots was completed in 2005, and in 2006
two joint publications on “Coherent Control and Polarization Readout of Individual Excitonic
States” and “Time- and spectrally-resolved four-wave mixing in single CdTe quantum dots”
have been prepared.
Task 2. Optical properties and relaxation kinetics of MC polaritons
(Lead team: Grenoble)
The Grenoble team has performed a number of unique experiments on Bose-Einstein
condensation of microcavity (MC) polaritons in CdTe-based nanostructures under
nonresonant optical excitations. The Paderborn team fabricated and characterised some of the
samples. The Grenoble team has developed a set-up which allows spectroscopic imaging in
real- and k- spaces to investigate the optical properties of microcavity polaritons. Relaxation
of polaritons along the dispersion curve has been studied as a function of the excitation
density using a nonresonant excitation pulse. In the low excitation regime, a marked
bottleneck effect at high in-plane k wavevectors is clearly observed. The related experimental
results were also obtained by the Dortmund team for GaAs-based microcavities. The latter
results deal with the polariton broadening in energy and momentum space measured as a
function of in-plane momentum: when optically exciting the lower polariton branch, the
strong dispersion versus wavevector results in a directional emission on a ring.
Fig. 1. Far-field emission of
a CdTe-based microcavity as
a function of the pumping
power, measured at T=5K.
The most remarkable result of the final year is the demonstration of Bose-Einstein
condensation of exciton polaritons in a CdTe-based microcavity. It has been made possible
through a close collaboration between the network teams of Grenoble and Cambridge, and the
EPFL team at Lausanne (B. Deveaud, Switzerland). The results will soon be published in
Nature.
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Experiments were performed at low temperature (5-40 K) on a CdTe-based microcavity
containing 16 quantum wells, using a spectroscopic imaging setup to probe the polariton
population in the momentum space. Under non-resonant and cw excitation, one can obtain
massive occupation of the polariton ground state, by either increasing the pump density (Fig.
2) or lowering the bath temperature (Fig. 3).
Fig. 2. Polariton distribution in the lower polariton branch at T=5K, as a function of the pump power P/P 0 = 0.84,
1.12 and 1.21 (P0 = condensation threshold power).
Fig. 3. Polariton distribution in the lower polariton branch for the same pump power, as a function of the
temperature, T = 16.5 and 10.4 K.
A more quantitative analysis of the polariton occupancy in the lower polariton branch is
displayed in Fig. 4 in a semi-logarithmic scale for various pump powers at T = 5 K. It can be
seen that close to condensation threshold (P = 0.86 Pthr), the occupancy can be fitted with a
Maxwell-Boltzmann distribution, indicating a polariton gas in thermal equilibrium at around
16 K. Above threshold, one can clearly observe a bimodal distribution marked by the
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saturation of the excited states and the formation of a condensate in the ground state. Such a
behavior is typical of Bose-Einstein condensation at finite temperature.
Fig. 4. Polariton occupancy measured at T = 5 K for various pump powers, P thr = condensation threshold power.
Teff is the polariton temperature.
At first sight, the observation of a polariton gas in internal thermal equilibrium could
appear puzzling considering the short polariton radiative lifetime (on the order of 10-12 s). In
fact, strong broadening of the polariton emission along the dispersion curve for pumping
around threshold indicates that the dephasing time due to polariton-polariton scattering is
shorter than the polariton lifetime by a factor 2 (not shown). Such a mechanism could indeed
permit attainment of internal thermal equilibrium before the escape of polaritons out of the
microcavity.
The critical density is estimated to be around 5.108 cm-2, which agrees well with the
theoretical threshold density for condensation at Teff = 16 K (see report of Cambridge team).
The expected spatial long range coherence and temporal coherence have been also observed
by using a Michelson interferometer.
All these results have been discussed with the Cambridge team (visits of Cambridge in
September 2005, January and July 2006, visit of Grenoble in April 2006), and presented at
the PMP workshop in Cambridge in June 2006.
The cooperation between the Cardiff and Cambridge teams has resulted in the suggestion
and development of a new field in the optics of semiconductor microcavities – resonant
acousto-optics of MC polaritons. Namely, in contrast with the conventional acousto-optics,
which usually deals with weak, nonresonant acousto-optical nonlinearities due to the
photoelastic effect, the proposed scheme exploits the excitonic states nearly resonant with the
acoustic and optical fields in the intra-band and inter-band transitions, respectively. As a
result, the large-value, resonant acousto-optical nonlinearities can be realised. The resonant
acousto-optic effect is particularly strong and well-defined for MC polaritons parametrically
driven by a surface acoustic wave (SAW). Recently, the resonant acousto-optic effect was
observed for SAW-driven MC polaritons (Paul-Drude-Institute, Berlin).
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Task 3. Interface-photon-mediated interaction of self-assembled quantum dots (QDs)
(Lead team: Cardiff)
The Cardiff and Dortmund teams have studied, both theoretically and experimentally, the
radiative corrections to the excitonic molecule (XX) state in GaAs-based microcavities. This
work is extremely important for the project, because for the first time the co-existence of the
MC and interface polaritons was demonstrated, and the importance of the “hidden” optics
associated with the evanescent light field of interface polaritons was proven. Namely, it turns
out that the radiative corrections to the XX state, the Lamb shift (a real part of the energy) and
radiative width (an imaginary part of the energy), are large, about 10%-30% of the molecule
binding energy and definitely cannot be neglected. Furthermore, we demonstrated that the
optics of excitonic molecules is dominated by the in-plane resonant dissociation of the
molecules into outgoing 1-lambda-mode and 0-lambda-mode cavity polaritons. It is the latter
decay channel, which deals with the short-wavelength MC polaritons invisible in standard
optical experiments, that refers to the “hidden” optics of microcavities.
The Cardiff team has also completed a theoretical study of the interface-photon-mediated
interaction of self-assembled or surface-deposited QDs (the Network YR, PhD student C.
Creatore was involved in this study). The conventional optics of interface (self-assembled) or
surface-deposited (colloidal) quantum dots (QDs) deals with the pump and signal light
associated with bulk photon modes. However, a long-distance coupling between the dipoleactive electronic states (excitons) in QDs also occurs by means of in-plane propagating
interface photons. The interface light is localized in the z-direction (the structure growth
direction) and invisible at macroscopic distances from the nanostructure. Thus the interface
photons contribute to the total optics of in-plane distributed QDs in a “hidden” way. We have
developed the interface, quasi-two-dimensional optics and described how the QDs
communicate via interface photons. The microscopic approach we used deals with in-plane
randomly-distributed QDs (Poisson statistics) which are inhomogeneously broadened in
energy (Gaussian statistics). The calculated eigen-spectrum of the Hamiltonian “bulk photons
+ QDs” allowed us to classify the eigenstates in terms of the rapidly decaying modes
(“radiative states”) and relatively weakly decaying modes (“interface photon-mediated QD
states”).
Fig. 4. Transition between the strong and the weak coupling limits for the quasi-particle solution in the 3D
space (Re[], Im[], k||). (g): the strong coupling limit. (h): the transition point. (i): the weak coupling limit .
In the final year, the Cardiff group has also studied how scattering processes relax the
coherent QW exciton -- photon coupling and change strong coupling regime to the weak one
(see Fig. 4).
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Weak-strong coupling polariton transition in a spherical photonic semiconductor dot has
been analysed by the Cardiff team. The developed approach to coherent polariton optics of a
spherical photonic dot (PD) for spatially dispersive and non-dispersive excitons shows that the
transition between the weak and strong coupling regimes results purely from changes in the
intrinsic radiative lifetime, which in turn depends upon the Rabi frequency, radius of the dot,
and dielectric constants of the dot and its surrounding medium. The discrete transition point is
attributed to the intersection of the polariton branches, which occurs at critical values of these
parameters. The transition point manifests as a discrete jump in the derivative of the radiative
linewidth, and its experimental observation using high precision modulation spectroscopy of a
CuCl PD is proposed. The pos-doctoral YR, Dr N. Nikolaev, was involved in this study.
Bragg diffraction of microcavity polaritons by a surface acoustic wave (SAW) was
proposed, analysed theoretically, and modelled numerically by the Cardiff team. Bragg
scattering of polaritons by a coherent acoustic wave is mediated and strongly enhanced by the
relevant exciton states resonant with the acoustic and optic fields in the intraband and
interband transitions, respectively. In this case, in sharp contrast with conventional acoustooptics, the resonantly enhanced Bragg spectra reveal the multiple orders of diffracted light,
i.e., a Brillouin band structure of parametrically driven polaritons can be directly visualized.
The above scheme was analyzed for polaritons in (GaAs) semiconductor microcavities driven
by a surface acoustic wave: for realistic values of the SAW, frequency = 1 GHz and acoustic
intensity less than 100 W/cm2, the main acoustically-induced band gap in the polariton
spectrum can be as large as 1 meV, and the Bragg replicas up to n=3 can be observed.
Furthermore, the resonant acousto-optic effect was proposed for TO-phonon polaritons. In this
case the acoustically changed restrahlen band and the acoustically induced spectral gaps in the
polariton spectrum can be used for frequency resolved detection of THz radiation [A. L.
Ivanov, in the book: Problems of condensed matter physics, Editors A. L. Ivanov and S. G.
Tikhodeev (Oxford University Press), in print].
A microscopic theory of photoluminescence, transport and thermalization of long-lived
indirect excitons in GaAs/AlGaAs coupled wells has been developed in order to explain a
recently observed so-called inner ring in the PL patterns. This work was done in cooperation
with the Cambridge team and with Prof L. V. Butov and his colleagues from UC San Diego
(USA).
Task 4. Disorder and decoherence effects in the optical response of photonic structures
(Lead team: Cambridge)
Much of the theoretical efforts of the Cambridge team was focussed on modelling
spontaneous coherence in semiconductor microcavities, particularly in context of the very
exciting experimental results of the Grenoble group. Several exchange visits between the
Cambridge and Grenoble groups (in both directions) were undertaken with a focus on the
analysis of data.
The focus of the strictly theoretical research on microcavity polariton physics over the
period of the research collaboration has been to start with a straightforward model of
interacting polaritons – the Dicke model – which can be solved at the mean field level, and
then to introduce realistic physical features so that real systems can eventually be addressed.
This programme, which was essentially completed, includes:
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- A full treatment of a model of localised excitons and propagating polaritons, including
a detailed model of disorder parametrized by experiment, and including also the effects of
two-dimensionality; this follows on from the work on the BCS/BEC crossover;
- A prediction of new signatures of condensation in resonant Rayleigh scattering;
- The first treatment of a phase transition in the Dicke model in an open, pumped
system, establishing that at the mean field level one may still have complete coherence even in
the presence of phase-breaking;
- The earlier understanding developed of the effects of dimensionality, disorder, and
decoherence were all critical in being able to contribute to a detailed analysis of the
experimental data in CdTe microcavities from the Grenoble group (published in Nature). In
particular, the measured blue shift cannot be understood without the effects of disorder, which
then allows one a separate calibration of the density to compare to direct photon counting
(which is difficult); the understanding of the lineshape depends on a realistic model for
decoherence; the understanding of the coherence length in the experiment depends upon a
proper 2D model (because there is no long-range order at non-zero T); and the understanding
of the transition temperature depends upon the proper inclusion of interactions – it turns out
that these systems are at a high enough density that simple non-interacting BEC is incorrect.
The Cambridge team has also studied Foerster-type energy transfer between an epitaxial
quantum well and a proximal monolayer of seminconductor nanocrystals (the post-doctoral
YR, Dr. Simon Kos, was involved in this study). The current technology enables to fabricate
semiconductor nanocrystals of high purity and a good size control, which, in turn, implies
control of the spectroscopic properties, and thus makes the nanocrystals well suited for optical
applications. However, injection of charge carriers into the nanocrystals is obstructed by a
passivation layer that protects surface of the nanocrystals. An alternative mechanism of charge
creation in the nanocrystals by energy transfer from a proximal quantum well was proposed.
In this case the rate of the energy transfer is comparable to the radiative recombination rate of
quantum-well excitation, which is the ultimate competing process.
Another investigation performed by the Cambridge team is accurate Quantum Monte
Carlo modelling of the phase diagram of the electron-hole system of an isotropic
semiconductor (2D and 3D cases). This study is a topic of the PhD thesis of P. Lopez Rios,
the pre-doc YR of the Cambridge team.
The Cardiff and Cambridge teams have also performed a (still preliminary) theoretical
study on disorder-induced change of the wavevector-frequency boundary between the
interface and bulk photon modes resonantly coupled with QW excitons.
Task 5. Spectroscopic methods for detection of interface light
(Lead team: Lund)
The Lund team has investigated random telegraph noise (RTN) in individual InP
quantum dots in GaInP where the photoluminescence is modulated and discovered a new type
of noise. The "old" type of RTN consisted of a modulation of the intensity of the
photoluminescence. The newly discovered noise consists of a shift of the emission lines
without any change of the total emission intensity. The Lund group has also developed a
comprehensive theory of which correlation functions can occur for electrons and also for
bosons. This is important for the calculation of few-particle effects in quantum dots and
quantum wires. Furthermore the Lund team has investigated the effect of etching on
individual quantum dots where clear effects of strain relief have been observed when the
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capping layer is removed from the dots. The strain effects on capped quantum wires have been
studied where the capping layer strains the core of the wire. These studies have been perfomed
on level of individual quantum wires (consisting of a GaAs core and a GaInP shell). All the
above research works were related to the interface light field associated with excitons in QDs,
QWells and QWires. The Lund team has observed that the emission lines from single InP
quantum dots shift with temperature, where the shift is dependent on the energy position of
the lines in a systematic way. The Lund team has also calculated the basic electronic structure
of most III-V quantum dots grown on most III-V substrates, as outlined in Task 5. In addition
the team has etched out dots in predefined places in pillars.
In the last two years, the Lund team has theoretically investigated pair-densities in manybody physics. This work has been concerned with characterising which functions of two
variables that can be a pair density. This is of fundamental importance for the calculation of
few- and many-body physics since it will lead to improved density functional theories. It has
been found that the pair-densities lie in a convex set and that the convex set becomes smaller
when the number of particles increases. Furthermore distance densities have also been
characterised and it has been proven that the distance densities that can arise from a
wavefunction have positive Fourier transforms. This is thus a necessary condition, but not
sufficient. Lately conditions on the eigenvalues of the pair-density, viewed as a HilbertSchmidt kernel has been found. These conditions are highly surprising and shows that the
problem is strongly connected with Random Matrix Theory. On the experimental side the
Lund group has investigated individual quantum dots of InAs on the surface of InP. These
dots emit in the deep infrared and a good correlation between the photoluminescence spectra
and theoretical calculations was found. The shape of the dots was determined by atomic force
microscopy. Finally, correlation spectroscopy of indvidual quantum dots of InP in GaInP has
also been performed allowing the identification of biexcitons and excitons. The polarisation
dependence of the exciton peaks was investigated and found to be in perfect agreement with
8-band k.p calculations.
Task 6. Materials Characterisation
(Lead team: Crete)
The Paderborn team has grown and sent to FORTH for Cross-section Transmission
Electron Microscopy (XTEM) three quantum dot samples (#1031, 1035, 1036) prepared by a
Stranski-Krastanow process, during the period of Dr H. Ouacha (a Network YR, Crete team)
secondment to Paderborn. These growths are part of the activities planned within Task 7
(Paderborn team) while the analyses are part of the activities within Task 6. The highlight of
these results: (a) The QDs were formed in all the specimens. However the best well defined
dots were observed in the specimen 1036, (b) The QDs were not periodic laterally or along the
growth, (c) Extended defects were not observed between the QDs and the matrix, and (d) In
the specimen 1035, ZnSe areas have the hexagonal structure. Following the successful
collaboration with the Paderborn team on the Cross-section Transmission Electron
Microscopy (XTEM) analyses of quantum dot samples prepared by a Stranski-Krastanow
process, during the period of Dr H. Ouacha (a Network YR, Crete team) secondment to
Paderborn, FORTH team has trained the new YR recruited after the departure of Dr Ouacha,
Ms M. Suchea from Romania. Ms Suchea was trained on the surface characterization of thin
films using SEM and AFM.
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Following the re-allocation of resources within the consortium, FORTH has undertaken
the task of fulfilling an additional 6 YR-month effort. The most closely related scientific area
for which a young researcher from Romania (Mr Valentine Tudose) was recruited was related
to the growth and characterization of 1D nanostructures of ZnO (nanorods) utilizing simple
chemical processing techniques.
Furthermore, in the same subject of Metal Oxide film characterization FORTH has
continued its effort to develop a new set-up for a reliable testing of their sensing
characteristics of ZnO and InOx utilizing Surface Acoustic Waves (SAWs). To this extent a
novel chamber was fabricated that would combine existing conductometric and new SAW
techniques while new masks were designed and fabricated to cover a range of frequencies
from 100 MHz to1GHz (see Fig. 5).
Fig. 5. A typical set-up (presented in the last meeting in Lund) for the SAW testing. This is one of the SAW
sensor structures wire bonded on a chip and the corresponding measuring setup. On the left side one can see as
SAW sensor structure fabricated at FORTH on a 36°-Y LitaO3, IDTs made from 20nmCr+200nmAu, transducer
periodicity 40μm, distance 810nm and 50 finger pairs.
Fig. 5. The sensing response of 100nm(top) and 20nm (bottom) InOx layered SAW sensor.
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Results on the sensing response of 100nm(top) and 20nm (bottom) InOx layered
SAW sensor towards a sequence of O3 pulses in synthetic air are presented in Fig. 6. O3
reduces the conductivity of InOx therefore the acoustic wave velocity increases and this is the
reason for observing an increase in the oscillation frequency. The frequency shifts of 30 to 80
KHz for the 100nm InOx SAW sensor@160C and of $0 to 50 KHz for the 20nm InOx SAW
sensor have been observed. These are very high sensitivities towards very low (in the ppb
range) O3 concentrations and the results make us very ambitious for obtaining measurable
responses towards sub-ppb concentrations, which would be state of the art for gas sensors.
The developed SAW technique is also relevant to resonant acousto-optic proposed and
developed by the Cardiff and Cambridge teams.
Task 7. Formation principles of II-IV Quantum Dots in microcavities
(Lead team: Paderborn)
The main scientific result of the Paderborn team was the deveplopment and MBEpreparation of ZnSe-based microcavities with CdZnSe-multi-quantum wells, which have
shown large Rabi-splitting at room temperature. The group demonstrated, for the first time,
that polariton devices, based on II-VI microcavities, can potentially operate at room
temperature (normal) conditions. The optimisation of the Bragg mirror processing was the
most crucial pre-request to achieve this result extremely important for possible technological
applications. The samples were optically characterized by the Grenoble group. The YR N.
Rousseau was fully integrated into this research work. In collaboration with the Crete-Team
cross-section Transmission Electron Microscopy (XTEM) studies have been performed, to
understand in more detail the formation kinetics of self-organized grown CdSe quantum dots.
In these experiments Dr. H. Ouacha (a Network YR, Crete team) was directly involved in the
MBE sample preparation. The results of these experiments allowed us to integrate CdSe-QDlayers in ZnSe-microcavity structures, according to the working plan.
In turn, the Grenoble team, using a new MBE process, has succeeded in obtaining a
clear Stranski-Krastanov growth mode for self-assembled CdTe and CdSe QDs. For both
types of QDs, no thermal activation of confined carriers is observed up to 150-200K. The
Grenoble group has also developed the technology for a hybrid microcavity based on
dielectric mirrors and ZnSe-based microcavities grown on GaAs substrates. This know-how
was shared with the Network partners.
Within “Paderborn-Dortmund” cooperation, the new epitaxial technique, the hybrid
growth of MBE using nanocrystals as colloidal seeds was further developed. The nanocrystal
concentration and wetting of the organic solution on a ZnSe substrate can now be controlled.
In close cooperation with the Paderborn group, Oliver Schöps from the Dortmund group has
measured concentration of the optical active nanocrystals and monitored blinking phenomena
before and after overgrowth. The results have been successfully presented at conferences and
a publication is in preparation.
As detailed above and discussed in Subsection B.3 (Breakdown of Tasks and
Milestones), our PMP Network was at the international state-of-the-art.
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A.2 Joint Publications and Patents
List of the PMP-Network publications
[1] N. Le Thomas, O. Schöps, B. Möller, U. Woggon, and M.V. Artemyev, Spectroscopy of
single CdSe nanorods, Technical digest of CLEO/IQCE, May 2004 San Francisco, USA.
[2] U. Woggon, R. Wannemacher, M. V. Artemyev, B. Möller, N. Le Thomas, V. Anikeyev,
and O. Schöps, Dot-in-a-dot: electronic and photonic confinement in all three dimensions,
Applied Physics B: Lasers and Optics 77, 469 (2003).
[3] B.M. Möller, U. Woggon, M. V. Artemyev, and R. Wannemacher, Photonic molecules
doped with semiconductor nanocrystals, Phys. Rev. B 70, 115323 (2004).
[4] W. Langbein, P. Borri, U. Woggon, V. Stavarache, D. Reuter, and A. D. Wieck,
Radiatively limited dephasing in InAs quantum dots, Phys. Rev. B 70, 033301 (2004).
[5] P. Borri, W. Langbein, U. Woggon, M. Schwab, M. Bayer, S. Fafard, Z. Wasilewski, and
P. Hawrylak, Exciton dephasing in quantum dot molecules, Phys. Rev. Lett. 91, 264701
(2003).
[6] P. Borri, W. Langbein, U. Woggon, A. Esser, J.R. Jensen, and J.M. Hvam, Biexcitons in
semiconductor microcavities, Semicond. Sci. Technol. 18, S351 (2003).
[7] B. Möller, U. Woggon, M. V. Artemyev, and R. Wannemacher, Mode control by
nanoengineering light emitters in spherical microcavities, Appl. Phys. Lett. 83, 2686 (2003).
[8] S. Schneider, P. Borri, W. Langbein, U. Woggon, J. Förstner, A. Knorr, R. L. Sellin, D.
Ouyang, and D. Bimberg, Self-Induced transparency in InGaAs quantum dot waveguides,
Appl. Phys. Lett. 83, 3668 (2003).
[9] A. Kudelski, K. Kowalik, J. Kasprzak, A. Golnik, J.A. Gaj, T. Wojtowicz, and G.
Cywiński, Magnetic field controlled in-plane optical anisotropy in parabolic (Cd,Mn,Mg)Te
quantum wells, Phys. Stat. Sol. (c) 1, 965 (2004).
[10] A. Smith, N. I. Nikolaev, and A. L. Ivanov, Coherent optics of spherical photonic dots:
weak and strong coupling regimes, Proceedings of the 27th International Conference on the
Physics of Semiconductors, edited by J. Menendez and C. Van de Walle, AIP Conference
Proceedings Volume 772 (American Institute of Physics, Melville, NY, 2005), pp. 757-758.
[11] F. M. Marchetti, B. D. Simons, and P. B. Littlewood, Condensation of Cavity Polaritons
in a Disordered Environment, Phys. Rev. B 70, 155327 (2004).
[12] M. H. Szymanska, P. B. Littlewood, and B. D. Simons, Polariton condensation and
lasing in optical microcavities – the decoherence driven crossover, Phys. Rev. A 68, 013818
(2003).
12
[13] J. Keeling, P. R. Eastham, M. H. Szymanska, and P. B. Littlewood, Polariton
condensation with localised excitons and propagating photons, Phys. Rev. Lett. 93, 226403
(2004).
[14] P. R. Eastham, M. H. Szymanska, and P. B. Littlewood, Phase locking in quantum and
classical oscillators: polariton condensates, lasers, and arrays of Josephson junctions, Solid
State Communications 127, 117-122 (2003).
[15] Mats-Erik Pistol, N-representability of correlation functions and density matrices, Condmat ./0406300 (2004).
[16] J. Persson, U. Hakansson, M. K. J. Johansson, L. Samuelsen and M-.E.Pistol, Strain
effects on InP quantum dots: Dependence of cap layer thickness, Phys. Rev. B 72, 085302
(2005).
[17] A. Pawlis, O. Husberg, A. Kharchenko, K. Lischka, and D. Schikora, Structural and
optical investigations of ZnSe based semiconductor microcavity structures, Phys. Stat. Sol. (a)
188, 983 (2001).
[18] A. Pawlis, A. Kharchenko, O. Husberg, D. J. As, K. Lischka, and D. Schikora, Large
room temperature Rabi-splitting in a ZnSe/(Zn,Cd)Se semiconductor microcavity structure,
Solid State Commun. 123, 235 (2002).
[19] A. Pawlis, A. Kharchenko, O. Husberg, D. J. As, K. Lischka, and D. Schikora, Large
room temperature Rabi-splitting in II-VI semiconductor microcavity quantum structures,
Microelec. Journal 34, 439 (2003).
[20] A. Pawlis, D. J. As, D. Schikora, J. Schörmann, and K. Lischka, Photonic devices based
on wide gap semiconductors for room temperature polariton generation (invited paper),
Phys. Stat. Sol. (c) 1, 5202 (2004).
-----------------------------------------------------------------------------------------------------------------Special issue of Journal of Physics: Condensed Matter, Vol. 16 (08 September 2004; for
details see http://www.iop.org/EJ/journal/-page=forthart/0953-8984/1)
[21] P. B. Littlewood, P. R. Eastham, J. M. J. Keeling, F. M. Marchetti, B. D. Simons, and M.
H. Szymanska, Models of coherent exciton condensation, pp S3597-S3620.
[22] A. L. Ivanov, Thermalization and photoluminescence dynamics of indirect excitons at
low bath temperatures, pp S3629-S3644.
[23] W. Langbein, Energy and momentum broadening of planar microcavity polaritons
measured by resonant light scattering, pp S3645-S3652.
[24] M. Richard, J. Kasprzak, R. Andre, L. S. Dang, and R. Romestain, Angle resolved
spectroscopy of polariton stimulation under non-resonant excitation in CdTe II-VI
microcavity, pp S3683-S3688.
13
[25] A. Pawlis, A. Kharchenko, O. Husberg, K. Lischka, and D. Schikora, Preparation and
properties of ZnSe/(Zn,Cd)Se multi quantum well microcavities for room temperature
polariton emission, pp S3689-S3694.
[26] N. I. Nikolaev, A. Smith, and A. L. Ivanov, Polariton optics of semiconductor photonic
dots: weak and strong coupling limits, pp S3703-S3720.
[27] M.-E. Pistol, InP quantum dots in GaInP, pp S3737-S3748.
[28] S. Osborne, P. Blood, P. Smowton, Y. C. Xin, A. Stintz, D. Huffaker, and L. F. Lester
Optical absorption cross section of quantum dots, pp S3749-S3756.
[29] G. Kiriakidis and N. Katsarakis, Photon sensitive high-index metal oxides films, S3757S3768.
----------------------------------------------------------------------------------------------------------------[30] W. Langbein, Spontaneous parametric scattering of microcavity polaritons in
momentum space, Phys. Rev. B 70, 205301 (2004).
[31] N. LeThomas, E. Herz, O. Schöps, U. Woggon, and M.V. Artemyev, Exciton fine
structure in single CdSe nanorods, Phys. Rev. Lett 94, 016803 (2005).
[32] U. Woggon, E. Herz, O. Schöps, M.V. Artemyev, C. Arens, N. Rousseau, D. Schikora,
K. Lischka, D. Litvinov, and D. Gerthsen, Hybrid epitaxial-colloidal semiconductor nanostructures, Nano Letters 5, 483 (2005).
[33] B. Möller, U. Woggon, and M. V. Artemyev, Coupled resonator optical waveguide
(CROW) doped with nanocrystals, Optics Letters 30, 2116 (2005).
[34] N. LeThomas, O. Schöps, U. Woggon, M. V. Artemyev, M. Kazes, and U. Banin, Cavity
QED with semiconductor nanocrystals, Nano-Letters 6, 557 (2006).
[35] B. M. Möller, U. Woggon, M. V. Artemyev, and R. Wannemacher, Photonic molecules
doped with semiconductor nanocrystals, Phys. Rev. B 70, 115323 (2004).
[36] N. Le Thomas, T. Selle, E. Herz, U. Woggon, and M. V. Artemyev, Line Shape Analysis
of Single Excitons and Trions in CdSe Nanorods, Technical Digest, CLEO/QELS 2005,
Baltimore, USA.
[37] M. Richard, J. Kasprzak, R. Romestain, R. André, and Le Si Dang, Spontaneous
coherent phase transition of polaritons in CdTe microcavities, Phys. Rev. Lett. 94, 187401
(2005).
[38] K. Cho, K. Okumoto, N.I. Nikolaev, and A. L. Ivanov, Bragg diffraction of microcavity
polaritons by a surface acoustic wave, Phys. Rev. Lett. 94, 226406 (2005).
[39] W. Langbein, Polariton correlation in microcavities produced by parametric scattering,
Phys. Stat. Solidi (b) 242, 2260 (2005).
14
[40] W. Langbein and B. Patton, Microscopic measurement of photon echo formation in
groups of individual excitonic transitions, Phys. Rev. Lett. 95, 017403 (2005).
[41] H. J. Pask, H. D. Summers, and P. Blood, Light-current characteristics of quantum dots
with localized recombination, Appl. Phys. Lett. 87, 083109 (2005).
[42] S. Cox, E. Rosten, J .C. Chapman, S. Kos, M .J. Calderon, D.-J. Kang, P. B. Littlewood,
P. A. Midgley, and N. D. Mathur, Strain control of superlattice implies weak charge-lattice
coupling in La0.5Ca0.5MnO3, Phys. Rev. B 73, 132401 (2006).
[43] M. Hruska, S. Kos, S. A. Crooker, A. B. Saxena, and D. L. Smith, Effects of strain,
electric and magnetic fields on latera electron spin transport in semiconductor epilayers,
Phys. Rev. B 73, 075306 (2006).
[44] S. Kos, M. Achermann, V. I. Klimov, and D. L. Smith, Different regimes of Foerstertype energy transfer between an epitaxial quantum well and a proximal monolayer of
semiconductor nanocrystals, Phys. Rev. B 71, 205309 (2005).
[45] S. Kos, A. J. Millis, and A. I. Larkin, Gaussian fluctuation corrections to the BCS meanfield gap amplitude at zero temperature, Phys. Rev. B 70, 214531 (2004).
[46] B. A. Davidson, R. Ramazashvili, S. Kos, and J. N. Eckstein, Broken Particle-Hole
Symmetry at Atomically Flat a-Axis YBa2Cu3O7-d Interfaces, Phys. Rev. Lett. 93, 107004
(2004).
[47] M.-E. Pistol, N-representability of two-electron densities and density matrices and the
application to the few-body problem, Chem. Phys. Lett. 400, 548-552 (2004).
[48] J. Persson , D. Hessman , M.-E. Pistol, W. Seifert, and L. Samuelson, Charging control
of InP/GaInP quantum dots by heterostructure design, Appl. Phys. Lett. 85, 5043-5045
(2004).
[49] N. Panev, M.-E. Pistol, J. Persson , W. Seifert, and L. Samuelson, Spectroscopic studies
of random telegraph noise in small InP quantum dots inGaxIn1-xP, Phys. Rev. B 70, 073309
(2004)
[50] C. Pryor and M.-E. Pistol, Band-edges diagrams for strained III-V semiconductor
quantum wells, wires and dots, Phys. Rev. B 72, 205311 (2006).
[51] Z. Zanolli, L. E. Jensen, M. T. Björk, M-E Pistol, and L. Samuelson, Fabrication, optical
characterization and modeling of strained core-shell nanowires, Thin Solid Films 515, 733
(2006).
[52] R. Marins, E. Fortunato, P. Nunes, I. Ferreira, A. Marques, M. Bender, N. Katsarakis, V.
Cimalla, and G. Kiriakidis, Zinc oxcide as an ozone sensor, J. Appl. Phys. 96, 1398 (2004).
[53] J. Androulakis, S. Gardelia, J. Giapintzakis, E. Gagaoudakis, and G. Kiriakidis, Indium
Oxide as Possible Tunnel Barrier in Spintronic Devices, Thin Solid Film 471, 293 (2005).
15
[54] M. Suchea, S. Christoulakis, M. Katharakis, N. Katsarakis, and G. Kiriakidis, Surface
characterization of ZnO transparent thin films, IOP, Journal of Physics: Conference series 10,
147 (2005).
[55] M. Richard, J. Kasprzak, R. André, R. Romestain, Le Si Dang, G. Malpuech, and A.
Kavokin, Experimental evidence for Bose condensation of exciton-polaritons, Phys. Rev. B.
72, 201301 (2005).
[56] J. Kasprzak, M. Richard, R. André, R. Romestain, G. Malpuech, A. Kavokin, and Le Si
Dang, Spontaneous phase condensaation of CdTe exciton-polritons, Phys. Stat. Sol. (c) 3, 797
(2006).
[57] J. Kasprzak, M. Richard, S. Kundermann, A. Baas, P. Jeambrun, J. Keeling, F. M.
Marchetti, M. H. Szymańska, R. André, J. L. Staehli, V. Savona, P. B. Littlewood, B.
Deveaud, and Le Si Dang, Bose-Einstein Condensation of Exciton Polaritons, to be published
in Nature.
[58] A. L. Ivanov, Resonant acousto-optical response of microcavity polaritons, Phys. Status
Solidi (a) 202, 2657-2663 (2005).
[59] L. E. Smallwood and A. L. Ivanov, In-plane diffusion and photoluminescence of in-direct
excitons, Phys. Status Solidi (c) 2, 3932-3935 (2005).
[60] A. L. Ivanov, L. E. Smallwood, A. T. Hammack, Sen Yang, L. V. Butov, and A. C.
Gossard, Origin of the inner ring in photoluminescence patterns of quantum well excitons,
Europhysics Letters 73, 920-926 (2006).
[61] C. Creatore and A. L. Ivanov, Weak and strong coupling limits for quantum well
polaritons, Phys. Status Solidi (c) 3, 2444-2448 (2006).
[62] A. T. Hammack, M. Griswold, L. V. Butov, L. E. Smallwood, A. L. Ivanov, and A. C.
Gossard, Laser induced trapping of excitons in coupled quantum wells, Phys. Rev. Lett. 96,
227402 (2006).
[63] A. L. Ivanov, N. I. Nikolaev, and K. Cho, SAW-driven microcavities for device
applications, IEE Proceedings Optoelectronics, in print (2006).
[64] A. L. Ivanov, Acoustically-induced superlattices: from electrons and photons to excitons
TO-phonones and polaritons, in the book: Problems of condensed matter physics, Editors A.
L. Ivanov and S. G. Tikhodeev (Oxford University Press,), in print.
[65] L. Mouchliadis, C. W. Lai, and A. L. Ivanov, Electric current induced anti-traps for
indirect excitons, Superlattices and Microstructures, submitted (2006).
[66] V. V. Temnov and U. Woggon, Superradiance and Subradiance in an Inhomogeneously
Broadened Ensemble of Two-Level Systems Coupled to a Low-Q Cavity, Phys. Rev. Lett. 95,
243602 (2005).
16
[67] B. Möller, U. Woggon and M. V. Artemyev, Coupled resonator optical waveguide
(CROW) doped with nanocrystals, Optics Lett. 30, 2116 (2005).
[68] B. Patton, U. Woggon, and W. Langbein, Coherent Control and Polarization Readout of
Individual Excitonic States, Phys. Rev. Lett. 95, 266401 (2005).
[69] N. Le Thomas, U. Woggon, W. Langbein, M. V. Artemyev, Effect of a dielectric
substrate on whispering gallery mode sensor, J. Opt. Soc. Am. B, submitted (2006).
[70] B. Patton, W. Langbein, U. Woggon, L. Maingault and H. Mariette, Time- and
spectrally-resolved four-wave mixing in single CdTe quantum dots, Phys. Rev. B 73, 235354
(2006).
[71] Ch. Arens, N. Roussau, D. Schikora, K. Lischka, O. Schöps, E. Herz, U. Woggon, D.
Litvinov, D. Gerthsen, and M. V. Artemyev, Colloidal nanocrystals integrated in epitaxial
nanostructures: structural and optical properties, phys. stat. sol. (c) 3, 861 (2006).
[72] N. LeThomas, U. Woggon, O. Schöps, M. V. Artemyev, M. Kazes, U. Banin, Cavity
QED with semiconductor nanocrystal, Nano Lett. 6, 557 (2006).
[73] O. Schöps, N. Le Thomas, U. Woggon, and M. V. Artemyev, Recombination dynamics
of CdTe/CdS core-shell nanocrystals, J. Phys. Chem. B 110, 2074 (2006) .
[74] B. Möller, U. Woggon, and M. V. Artemyev, Photons in coupled microsphere
resonators, J. Opt. A: Pure Appl. Opt. 8, S113-S121 (2006).
[75] M.-E. Pistol, Relations between N-representable n-particle densities, Chem. Phys. Lett.
422, 363-366 (2006).
[76] M.-E. Pistol, Characterization of N-representable n-particle densities when N is infinite,
Chem. Phys. Lett. 417, 521-523 (2006).
[77] M.-E. Pistol, N-representable distance densities have positive Fourier Transform,
Chem. Phys. Lett., submitted (2006).
[78] C. Ellström, J. Trägårdh, L. Samuelson, W. Seifert, M.-E. Pistol, S. Lemeshko, and C.
Pryor, Investigations of InAs surface dots on InP, Appl. Phys. Lett. 89, 033111 (2006).
[79] R. Marins, E. Fortunato, P. Nunes, I. Ferreira, A. Marques, M. Bender, N. Katsarakis, V.
Cimalla, and G. Kiriakidis, Zinc oxcide as an ozone sensor, J. Appl. Phys. 96, 1398 (2004).
[80] J. Androulakis, S. Gardelia, J. Giapintzakis, E. Gagaoudakis, and G. Kiriakidis, Indium
Oxide as Possible Tunnel Barrier in Spintronic Devices, Thin Solid Film 471, 293 (2005).
[81] M. Suchea, S. Christoulakis, M. Katharakis, N. Katsarakis, and G. Kiriakidis, Surface
characterization of ZnO transparent thin films, IOP, Journal of Physics: Conference series 10,
147 (2005).
17
[82] F. M. Marchetti, J. Keeling, M. H. Szymanska, and P. B. Littlewood, Thermodynamics
and excitations of condensed polaritons in disordered microcavities, Phys. Rev. Lett. 96,
066405 (2006).
[83] F. M. Marchetti, J. Keeling, M. H. Szymanska, and P. B. Littlewood, Absorption,
Photoluminescence and Resonant Rayleigh Scattering Probes of Condensed Microcavity
Polaritons, submitted to Phys. Rev. B (2006).
[84] M. H. Szymanska, J. Keeling, and P. B. Littlewood, Nonquilibrium Quantum
Condensation in an Incoherently Pumped Dissipative System, Phys. Rev. Lett. 96, 230602
(2006).
[85] J. Keeling, Response functions and superfluid density in a weakly interacting Bose gas
with nonquadratic dispersion, Phys. Rev. B, in print (2006).
[86] P. B. Littlewood and S. Kos, Focus on the Fermi surface, Nature (News and Views),
438, 435 (2005).
[87] M. Hruska, S. Kos, S. A. Crooker, A. Saxena and D. L. Smith, Effects of strain, electric,
and magnetic fields on lateral electron spin transport in semiconductor epilayers, Phys. Rev.
B 73, 075306 (2006).
[88] S. Cox, E. Rosten, J. C. Chapman, S. Kos, M. J. Calderon, D. J. Kang, P. B. Littlewood,
P. A. Midgley, and N. D. Mathur, Strain control of superlattice implies weak charge-lattice
coupling in La0.5Ca0.5MnO3, Phys. Rev. B 73, 132401 (2006).
[89] P. Lopez Rios, A. Ma, N. D. Drummond, M. D.Towler and R. J. Needs, Inhomogeneous
backflow transformations in quantum Monte Carlo, Phys.Rev. E, in press (2006).
[90] N. D. Drummond, P. Lopez Rios, A. Ma, J. R. Trail, G. G. Spink, M. D. Towler, and R.
J. Needs, Quantum Monte Carlo study of the Ne atom and the Ne+ ion, J.Chem.Phys. 124,
224104 (2006).
In addition, a special issue of Journal of Physics: Condensed Matter (a special issue on
optical coherence and collective phenomena in nanostructures) will be published in the end
2006 -- beginning 2007 as a Proceeding of our Seventh PMP Network Workshop. The Editors
of the issue are the PMP Network members (P. B. Littlewood, F. M. Marchetti and M. H.
Szymanska). A similar issue was published in 2004, right after the First PMP Network
Workshop [J. Phys.: Cond. Matter 16, No 35 (2004) edited by A. L. Ivanov, the PMP Network
coordinator]:
[91] P. Borri and W. Langbein, Coherent dynamics of excitons in InGaAs self-assembled
quantum dots.
[92] P. R. Eastham, The new physics of non-equilibrium condensates: insights from classical
dynamics.
[93] C. Ellström, W. Seifert, C. Pryor, L. Samuelson, M.-E. Pistol, Exciton fine structure
splitting in InP quantum dots in GaInP.
18
[94] J. Keeling, Coulomb interactions, gauge invariance, and phase transitions of the Dicke
model.
[95] L. Mouchliadis and A. L. Ivanov, Anti-trapping of indirect excitons by a current filament.
[96] Z. Zanolli, B. A. Wacaser, M.-E. Pistol, K. Deppert and L. Samuelson, Core-shell InPCdS nanowires: fabrication and study.
[97] Z. Zanolli, M.-E. Pistol, L. E. Fröberg and L. Samuelson, Quantum confinement effects in
InAs-InP core-shell nanowires.
[98] C. Creatore and A. L. Ivanov, Effect of damping on the properties of exciton-polaritons
in quantum wells.
PMP Network Patent:
[99] M. V. Artemyev, E. Herz, K. Lischke, D. Schikora, and U. Woggon, “Verfahren zur
Integration von kolloidal erzeugten Nanopartikeln in epitaktische Schichten”, DE 10 2004 008
065.8, February 19, 2004.
Conference Presentations of PMP-Network Young Researchers
A. Kudelski, O. Krebs, J. Kasprzak, G. Cywiński, P. Voisin, and J.A. Gaj, Giant in plane
optical anisotropy induced by longitudinal magnetic Cd1-xMnxTe, International Conference on
Physics of Semiconductors, Edinburgh 2002.
J. Siwiec-Matuszyk, J. Kasprzak, A. Babinski, and M. Baj, Intersubband scattering in
pseudomorphic GaAs/InGaAs/AlGaAs structure, XXXI International School of
Semiconducting Compounds, Jaszowiec 2002.
N. Le Thomas, O. Schöps, M.V. Artemyev, and U. Woggon, CdSe doped Micro-Spheres:
Candidates for a Thresholdless Laser, 304th WE-Heraeus-Seminar (Elementary QuantumProcessors) , 13-15 October 2003.
J. Kasprzak, M. Richard, Le Si Dang, R.Romestain, R. Andre, and J.A. Gaj, Polariton effects
in II-VI semiconductor microcavities, VIII Workshop on Physics of Semimagnetic
Semiconductors, Obory 2003.
J. Kasprzak, M. Richard, Le Si Dang, R.Romestain, R. Andre, and J.A. Gaj, Stimulation
phenemena in II-VI semiconductor microcavities, XXXII International School on the Physics
of Semiconducting Compounds, Jaszowiec 2003.
F. Boeuf, M. Miller, M. Richard, R. Andre, J. Bleuse, Le Si Dang, and J. Kaprzak, R.
Romestain, “Polariton Laser: contribution of CdTe based microcavities”, Les Houches
summmer school, 2003.
19
C. Creatore , poster presented at the “International Summer School on Functional
Nanostructures”, Karlsruhe, Germany, September 2003.
M. Suchea and G. Kiriakidis, “Atomic Force Microscopy Analysis of Polycrystalline Indium
Oxide Thin films”, poster presented in XIX National Conference in Solid State and Material
Science, Tessaloniki Greece,21-24 September 2003.
N. Le Thomas, E. Herz, M.V. Artemyev, and U. Woggon, Micro-Photoluminescence of single
CdSe nanorods , Quantum Dot 2004 Banff/Canada , 9-14 May 2004.
N. Le Thomas, E. Herz, M.V. Artemyev, and U. Woggon, Engineering of Exciton-Photon
Coupling in micro-spheres, International Workshop on Solid State Based Quantum
Information Processing QIP 2004, 2004, Herrsching, Bavaria, 13rd-17th September 2004.
N. Le Thomas, E. Herz, O. Schöps, M.V. Artemyev, W. Langbein, and U. Woggon, Lowtemperature spectroscopy of single CdSe nanorods: Fine structure and polarization
properties, MRS meeting, Boston, 29th-3rd December 2004.
B. Möller, N. Le Thomas, M.V. Artemyev, and U. Woggon, Nanocrysal-doped polymer
spheres as building blocks for coupled resonator optical waveguides MRS meeting, Boston,
29th-3rd December 2004.
O. Schöps, E. Herz, B. Möller, N. Le Thomas, M.V. Artemyev, and U. Woggon, Shapecontrol of the optical selection rules in CdSe nanorods, MRS meeting, Boston, 29th-3rd
December 2004.
C. Creatore, oral presentation at “SIOE, Semiconductor and Integrated OptoElectronics”,
Cardiff, U.K, April 2004.
M. Richard, J. Kasprzak, R. André, R. Romestain Le Si Dang, Polariton stimulation and
condensation in semiconductor microcavities, 20th General Conference of the Condensed
Matter Division of the European Physical Society, Prague, Tchek Republic, 17-23 July, 2004.
M. Richard, J. Kasprzak, R. André, R. Romestain, and Le Si Dang, Spontaneous build-up of
polariton coherence in semiconductor microcavities, 1st International Conference on
Spontaneous Coherence in Excitonic Systems, Seven Springs (Pennsylvanie), USA, May 2004.
M. Richard, J. Kasprzak, R. André, R. Romestain, and Le Si Dang, Coherent phase transition
in CdTe microcavities, E-MRS Fall Meeting, Warsaw, Poland, September 2004.
M. Richard, J. Kasprzak, R. André, R. Romestain, and Le Si Dang, Towards evidence of
spontaneous polariton condensation in II-VI microcavities, 4th International Conference on
Physics of light-matter coupling in nanostructures, Saint Petersburg, Russia, 29 June-3 July,
2004.
Creatore and A. L. Ivanov, Collective interface-photon-mediated states of in-plane
distributed quantum dots, QEP-16 PHOTON 04, Glasgow, U.K., September 2004.
S. Kos, Gaussian fluctuation corrections to the BCS mean-field gap amplitude at zero
temperature, 2005 APS March Meeting.
20
S. Kos, Effects of strain, electric and magnetic fields on electron spintransport in
semiconductor epilayers, LT24 2005.
S. Kos, Different regimes of Foerster-type energy transfer between an epitaxial quantum well
and a proximal monolayer of semiconductor nanocrystals, , Seminar at Columbia University,
New York, 2005.
S. Kos, Specific heat at the transition in a superconductor with fluctuating magnetic moments,
Low-temperature group seminar in Cambridge, 2005.
P. Lopez-Rios, Backflow corrections in QMC: going beyond the Slater-Jastrow wave-function
in real systems, given at the TCM group, Cambridge, 2005
P. Lopez-Rios, Studying the electron-hole phase diagram, given at TTI, Tuscany, Italy, 2005.
Z. Zanolli, talk at ACSIN-8, Stockholm, June 2005.
N. Le Thomas, O. Schöps, U. Woggon, M. V. Artemyev, M. Kazes, U. Banin, CQED with
semiconductor nanocrystals, QELS 2006, Long Beach, USA, 2006.
N. Le Thomas, O. Schöps, M.V. Artemyev and U. Woggon, Cavity QED with Single CdSe
Nanorods, QD 2006, Chamonix, France 2006.
O. Schöps, N. LeThomas, M.V.Artemyev, U.Woggon, Excitonic fine structure of colloidal IIVI nanocrystals: Size and shape dependent recombination dynamics, QD 2006, Chamonix,
France 2006.
O. Schöps, Ch. Arens, D. Schikora, K. Lischka, M.V. Artemyev, U. Woggon, Colloidal
Nanocrystals Integrated in Epitaxial Nanostructures: Structural and Optical Properties, QD
2006, Chamonix, France 2006.
Ch. Arens, O. Schöps, M. V. Artemyev, D. Schikora, K. Lischka, U. Woggon , Self organized
grown Stranski Krastanow II-VI quantum dots vs. colloidal nanocrystals integrated in
epitaxial nanostructures, ICPS 28, Vienna, Austria 2006.
C. Creatore and A. L. Ivanov, Weak and strong coupling limits for quantum well polaritons,
Nonlinear Optics and Excitation in Semiconductors NOEKS8, Muenster, Germany, Febraury
2006.
S. Kos, Spin noise of itinerant fermions, 2006 APS March Meeting.
S. Kos, Weak coupling of the charge order to the lattice in La1-xCaxMnO3 close to x=0.5,
Third meeting of the EU project "Controlling Mesoscopic Phase Separation", Paris, June
2006.
S. Kos, Spins under strain, Quantum Complexities in Condensed Matter, Cambridge, July
2006.
S. Kos, Spins under strain, Florida State University, Tallahassee, Florida, USA, March 2006.
S. Kos, Spins under strain, University of California, Santa Barbara, California, USA, March
2006.
21
S. Kos, Spins under strain, University College London, May 2006.
P. Lopez-Rios, Inhomogeneous backflow transformations in QMC, APS March meeting,
Baltimore, USA, 2006, and at the TTI, Tuscany, Italy.
P. Lopez-Rios, Inhomogeneous backflow transformations in QMC, TTI, Tuscany, Italy, 2006.
P. Lopez-Rios, Inhomogeneous backflow transformations in QMC, Electronic structure winter
workshop, Robinson College, Cambridge, UK, 2006.
Z. Zanolli, Ab initio study of InAs and GaAs with wurtzite crystal structure, Helsinki
University of Technology, Laboratory of Physics – Computational Nanoscience, Helsinki,
Finland, May 22, 2006.
Z. Zanolli, Ab initio study of InAs and GaAs with wurtzite crystal structure, Université
Catholique de Louvain, Unité de Physico-Chimie et de Physique des Matériaux, Louvain-laneuve, Belgium, April 12, 2006.
B.A. Wacaser, K.A. Dick, Z. Zanolli, K. Deppert, and L. Samuelson, Size-Selected compound
semiconductor quantum dots by nanoparticle conversion, ACCGE 16 and OMVPE 12, July
10–15, 2005, Big Sky, Montana, USA.
Z. Zanolli and U. von Barth, InAs with wurtzite crystal structure: full-potential and
psedopotential ab-initio calculations, 5th Oresund meeting on quantum transport, May 15,
2006, Lund, Sweden.
Z. Zanolli and U. von Barth, InAs with wurtzite crystal structure: full-potential and
psedopotential ab-initio calculations, DFTEM 2006 – 12th WIEN2k WORKSHOP, April 19–
23, 2006, Wien, Austria.
M-E Pistol, C. Pryor, Z. Zanolli, N. Sköld, L. Fröberg, M.Björk, L. Samuelson, Theoretical
and optical investigations of strained core-shell quantum wires, The Nanophysics and
Nanoelectronics Symposium 2006, March 13 -17, 2006, Nizhny Novgorod, Russia.
Z. Zanolli, L.E. Jensen, M.T. Björk, M-E Pistol, and L. Samuelson, Fabrication, optical
characterization and modeling of strained nanowires, ACSIN-8/ICTF-13, June 19-23, 2005,
Stockholm, Sweden.
M. Suchea, S. Christoulakis, I.V. Tudose, D. Vernardou, M.I. Lygeraki, S. H. Anastasiadis, N.
Katsarakis and G. Kiriakidis, Pure and Nb2O5 doped TiO2 amorphous thin films grown by dc
magnetron sputtering at room temperature: surface and photoinduced hydrophilic conversion
studies, International Conference on Coatings on Glass and Plastics, June 18-22, Dresden,
Germany, 2006.
In addition, all the young researchers usually attended our regular (biannual) Network meetings.
22
PART B - COMPARISON WITH THE PROJECT PROGRAMME
B.1 Research Objectives
State whether the research objectives, as set down in the project programme of
contract, are still relevant and achievable. If not, explain why.
All the research objectives formulated in Annex I of our Network research programme
(see also our website) have successfully been achieved.
B.2 Methodological Approach and Work Plan
Has the methodological approach changed from that described in the contract? If so,
how? Using charts and diagrams only, illustrate how the joint programme of work is
broken down into tasks and which teams are involved in each task. Explain any
significant differences from the work plan envisaged in the contract.
The methodological approach of the PMP-Network has not been changed in comparison with
that detailed in our initial proposal. The research programme was broken down into the seven
tasks according to our original plan. See the relevant webpage of our website:
http://www.astro.cardiff.ac.uk/research/PMPnetwork/network/projectobj.htm
B.3 Schedule and Milestones
The PMP-Network schedule was consistent with that we put in our original proposal. The
research works, training programme, Network meetings and workshops proceeded according
to the initial plan.
Breakdown of tasks and Milestones:
1. The experimental demonstration of the highest coupling efficiency of spontaneous
emission (beta-factor) ever observed for semiconductor nanocrystals. The first realisation
of the strong coupling regime for CdSe nanorods embedded in a spherical microcavity; the
Q-factor of about 200 000 was achieved.
2. The unique experiments on energy relaxation of MC polaritons in CdTe-based
nanostructures under nonresonant optical excitations.
3. New real-/k-space and resonant Rayleigh spectroscopies of semiconductor microcavities.
As a result, discovery of “polariton rings” in both CdTe-based and GaAs-based MCs.
4. The new epitaxial technique, the hybrid growth of MBE using nanocrystals as colloidal
seeds.
23
5. The mean-field (macroscopic) and first-principle (microscopic) theories of the long-range
interface-photon-mediated interaction of self-assembled or surface-deposited QDs. Hidden
optics associated with in-plane distributed QDs.
6. The suggestion and development of a new field in the optics of semiconductor
microcavities – resonant acousto-optics of MC polaritons.
7. The unique optical experiments with InP QDs in predefined places on the top of nanopillars.
8. The models of polariton condensation and lasing in optical microcavities.
9. The microscopic theory of decoherence of single-mode MC polaritons.
10. The theoretical models of relaxation kinetics and in-plane transport of statisticallydegenerate electrons, holes and indirect excitons in coupled QW.
11. The first observation of the MC polariton effects at room temperature (ZnSe-based
microcavities).
12. The radiative corrections to the excitonic molecule state in (GaAs-based) microcavities
have been for the first time calculated and measured.
13. The theoretical investigation of the single-mode excitonic polaritons in photonic dots:
intrinsic transition between the strong and weak coupling regimes.
14. The high-precision XTEM technique for characterization and selection of nanostructures.
15. The discovery of new RTN (random telegraph noise) in photoluminescence of InP QDs.
16. An effective SAW-induced Bragg diffraction of microcavity polaritons was proposed and
calculated.
17. A theoretical analysis of the spin flow in semiconductors.
18. The resonant acousto-optical effect for TO-phonons was proposed.
19. First observation of Bose-Einstein condensation of polaritons in CdTe-based microcavities
(paper in Nature).
20. Pair-density functional approach to many-body problem in solids was developed.
21. Coherent control and polarization readout of individual exciton states was realized.
B.4 Research Effort of the Participants
The research effort of the Network teams is described in detail in the Sections A.1 (Scientific
Highlights), B.3 (Schedule and Milestones), B.6 (Network Organisation and Management)
and Part C (Training). The collaborative research links are schematically shown in the chart
placed below. There were no significant variations with the initial PMP-Network plan.
24
B.5 Cohesion with Less Favoured Regions
Are any of the network partners from less favoured regions of the community? If so,
explain the efforts that have been made to integrate them into the project.
The Crete team, which is from EC Less Favoured Regions, had a very important role in the
PMP-Network: it is responsible for characterization and selection of various photonic nanostructures provided by other Network-teams (Paderborn and Dortmund). By putting the
Cardiff team to coordinate the Network, we also promoted Welsh physics, in particular, optoelectronics, to the best European standards.
B.6 Network Organisation and Management
The PMP Network organisation and management exactly followed our initial approach and
are detailed at our Network website:
http://www.astro.cardiff.ac.uk/research/PMPnetwork/index.html (see also the schematic).
Schematic of the PMP Network structure and management.
25
Major Network meetings and workshops
(1) An introductory meeting of the Network lead members took place at Cardiff in May 2002,
just before the start date of the project. We have discussed the Network research tasks, our
future cooperations and the relevant organising questions. Prof Leonid V. Keldysh (Physics
Institute, RAS, Moscow), an internationally leading expert in semiconductor physics, attended
the meeting and contributed a lot to the discussions of the scientific programme.
(2) The first working meeting “Photon-Mediated Phenomena – 1st Network Conference”
(28.03-31.03.2003, Gregynog, Wales) was organised by the Cardiff team, according to the
Workplan. Apart from the Network members, many leading experts in semiconductor optics
have contributed to the meeting by giving overview talks and by participating in various
Network-related discussions: Profs H. Akiyama (ISSP, Tokyo University), K. Cho (Osaka
University), S.-L. Chuang (University of Illinois), A. Kavokin (LASMEA, France), L. Levitov
(MIT, USA), M. S. Skolnick (University of Sheffield), D. Snoke (University of Pittsburgh,
USA), S. G. Tikhodeev (General Institute of Physics, RAS, Moscow), V. B. Timofeev (ISSP,
RAS, Chernogolovka), and Drs F. Laussy and I. Shelykh (LASMEA, France). All together, 43
participants attended the meeting. The conference was very successful, and the Proceedings
will be published in a special issue of Journal of Physics: Condensed Matter. The details of
the meeting (its program, list of participants etc.) are on our web site.
(3) The second working meeting “Photon-Mediated Phenomena – 2st Network Conference”
was organized by the Crete team, according to the Workplan, and took place at Hersonissos,
Crete, October 24-25, 2003. All the groups were represented (about 20 attendees) and an
overall number of thirteen contributed talks were presented both by senior members of the
groups as well as by YRs (for details see the Network website). The meeting generally rated as
very successful, was rounded up by an extensive discussion coordinated by Prof. A. L. Ivanov
covering issues related to current scientific progress and achievements as well as plans for
further strengthening collaborative work and exchange activities.
(4) The Mid-Term-Review Meeting of the PMP Network is planned to be at Cardiff, on
August 31, 2004. Over 25 participants, including all the senior and young researchers of the
Network, an EU RTN scientific officer (Dr. R. Bilyalov), external scientific expert (Prof. K.
Cho, Japan), pro-VC of Cardiff University (Prof. P. Blood), are going to attend this important
meeting.
(5) The Third and Fourth Workshops, organised by Detlef Schikora and Ulrike Woggon, was
held in Paderborn (conference part) and Dortmund (training part) from
October 4th through to October 7th, 2004.
(6) The Fifth PMP Workshop, organised by Le Si Dang, was held in Autrans (France) from
June 11th through to June 12th: 26 participants including 4 invited speakers: L. Besombes
(Universite J. Fourier - CNRS Grenoble), P. Senellart (LPN, CNRS Marcoussis), T. Kuhn
(University Muenster), Ounsi el Daif (EPFL, Lausanne).
(7) The Sixth Workshop, organised by Prof. Mats-Erik Pistol, was held in Lund, from March
24th to March 26th, 2006. It consisted of a conference part and a training (this latter held in
the Experimental Solid State Division of the Physics Department of Lund University). Apart
26
from talks given by Network members, tutorials were given by external invited speakers: Prof.
L. Butov from University of San Diego (USA) about condensation in cold exciton gases and
Prof. D. Gershoni from the Israel Institute of Technology at Haifa about entanglement of
photon pairs in quantum dots. About twenty researchers have attended the meeting.
(8) The last Network Workshop, organised by the Cambridge team, was held in Cambridge,
from 23rd to 25th June 2006. It was mainly talk oriented and many important invited speakers
gave tutorial talks. Among them, Sir Prof. R. Friend from Cambridge spoke about the new
prospective in molecolular semiconductors, Prof. Aron Pinczuk from Columbia University
(USA) showed his research about Quantum Hall fluids, and Profs. L. Butov and D. Snoke
(both from USA) discussed their recent studies in the field on indirect excitons in Quantum
Wells. All the contributions from both invited and team-members speakers have been
collected in a special issue of the Institute of Physics publication, “Journal of Physics:
Condensed Matter” which will be published in the very end 2006 (or the very beginning
2007). About forty researchers have attended the meeting.
Summary of the PMP-Network visits (2002-2006)
From/
To
Cardiff
Crete
Cambridge
Lund
Dortmund
Paderborn
Grenoble
Cardiff
Crete
3
3
18
6
6
4
1
1
1
2
Cambridge
4
2
4
4
4
14
Lund
6
1
3
2
2
2
Dortmund
5
2
1
Padernborn
1
2
1
3
7
4
Grenoble
3
3
8
1
1
1
2
B.7 Connections to Industry
Describe the involvement of industry in the network. List all companies that have had
a meaningful interaction with the network, explaining in each case the nature of that
interaction (information exchange, participation in meetings, involvement in the
training programme, possible exploitation of results ...). Explain any significant
changes in the involvement of industry from that foreseen in the contract.
There is one PMP-Network patent, filed by the Dortmund and Paderborn teams: M.V.
Artemyev, E. Herz, K. Lischke, D. Schikora, and U. Woggon, “Verfahren zur Integration von
kolloidal erzeugten Nanopartikeln in epitaktische Schichten”, DE 10 2004 008 065.8,
February 19, 2004, which is now extended to Europe and USA.
The resonant acousto-optics, proposed and developed by the Cardiff and Cambridge
teams, can result in a new generation of effective acousto-optical elements. Such devices can
potentially lead to a new high-tech industry in the EU.
27
PART C - TRAINING
C.1 Employment of Young Researchers
In a table similar to that below, summarise the number of young researchers (in manmonths) whose employment has so far been financed by the contract and compare it
with the overall deliverable specified in the contract.
Participant
Contract deliverable of Young
Researchers to be financed by the
contract (person- months)
Young Researchers financed by the
contract so far (person-months)
Pre-doc
(a)
Post-doc
(b)
Total
(a+b)
Pre-doc
( c)
Post-doc
(d)
Total
(c+d)
Cardiff
36
30
66
42
31
73
Cambridge
36
24
60
36
24
60
Grenoble
36
12
48
37
12
49
Paderborn
18
18
36
0
18
18
Dortmund
0
36
36
3
36
39
Crete
0
24
24
8
26
34
Lund
0
24
24
0
36
36
126
168
294
126
183
309
TOTAL
Explain any cases where the rate of employing young researchers is falling well below
what is expected under the contract. Explain, in particular, in such cases how the
vacancies have been published.
The Network positions were widely advertised via Tip-Top, DFG and Network web sites as
well as through network of collaborating institutes all over Europe sending e-mails and
distributing the existence of vacancies in local and international meetings. We got a lot of
applications (more than two hundred). The 18 month pre-doc position of the Paderborn
team was not filled and therefore was re-distributed among other teams (Cardiff,
Create, Grenoble and Dortmund). The training programme of young researchers was
successfully fulfilled with even more Post-doc training months!
C.2 Training Programme
There has been a solid integration of young researchers into our Network. In particular, the
first and second Network meetings (Gregynog, March 2003 and Hersonnisos, October 2003)
28
have provided the YRs with excellent overview talks, done by the internationally leading
experts in the field of semiconductor optics, on the research subjects. The YRs of the Cardiff
team were involved in a special set of lectures on quantum solid state theory. Mr C. Creatore
(pre-doc, Cardiff team) has attended a one-week summer school on functional nanostructures
(Bad Herrenalb, Germany). YRs C. Creatore (Cardiff) and M. Suchea (Crete) attended one
week summer school “2004 Lectures in Chemistry and Physics: The Nanotechnology Revolution”
organized by the “Onassis Foundation” in July 2004. Pablo L Rios (YR of the Cambridge team) has
participated in the work of the ICTP Winter School on QMC methods (International Centre
for Theoretical Physics, Trieste, Italy, winter 2003/2004). In order to be integrated better into
the Crete team, M. Suchea (YR of the Crete team) attended Greek Lessons for foreigners,
medium level at Philology Department of Crete University, Special Open course:
"Semiconductor based microsensors" at Physics Department of Crete University and
International NATO Conference, Hersonissos (Crete, September 2003). She also attended
regular graduate level classes offered by the Physics Department of the University of Crete.
Zeila Zanolli (YR of the Lund team) was a student of “Summer-School on Semiconductor
Quantum Dots: Physics and Devices”, Monte Veritá, Ascona (Italy, September 2004). She
was also trained in operating and setting up an infrared micro-PL setup, as well as in
measurements of individual quantum dots and quantum wires.
Dr N. Nikolaev (post-doc YR, Cardiff team) contributed to supervision of A. Smith, a
research student in Cardiff. The Dortmund team has involved Dr N. Le Thomas into the
training in experiments on micro-PL and time-resolved PL, led by Dr W. Langbein. Prof U.
Woggon gave an extended introduction to published literature concerning optics of
microspheres and spectroscopy of QDs. Dr N. Le Thomas was involved in supervision of
research students. He has also attended the 304 Hereaus-School on elementary quantum
processors (Bonn, Germany). The young researcher of the Lund team (Dr M. Cazayouz) was
introduced into the research area by learning micro-photoluminescence, electron beam
lithography, and etching techniques to isolate individual quantum dots. In the Crete team both
post and pre-doc YRs have had the chance to get an in-depth training on thin film growth
techniques utilizing conventional evaporation and sputtering systems, while they got an
individual training on specific characterization techniques. Dr H. Ouacha was trained on
optical techniques utilizing a VIS/UV spectrophotometer for the study of the film absorption
edges, while Ms M. Suchea got trained on surface topography technique utilizing atomic force
microscopy. Dr H Ouacha was also trained by the Paderborn group (Dr. D. Schikora) in the
epitaxy and optical characterization of Quantum Dot structures.
After his leaving to EPFL Lausanne, an intense research collaboration has established
with the Dortmund group and the former YR Nicolas LeThomas. He was involved in the
training of Marco Allione on physics of CdTe-based nanocavities. The Dortmund team
received additional funds from an intern network transfer and could offer three person month
to a PhD-student. These funds have been allocated to Jordi Gomes from Spain who worked in
Dortmund from May 1 until July 31. In these three month Jordi Gomes was trained in
different techniques of ultrafast spectroscopy and took part on experiments to study quantum
dot dynamics. Mr V. Tudose a chemist from Romania was oppointed (Crete team) at a short
notice for six months to undertake the task of growing nanostructured ZnO rode applying
chemical synthesis and characterization of ZnO nanostructured compounds for different
applications. He developed a chemical route for ZnO nanostructures and thin films growth and
gained experience on XRD characterization, optical and spectroscopic techniques as well as
surface characterization using SPM image processing. He became familiar with dc magnetron
sputtering and thermal evaporation thin films growth techniques. Besides ZnO, he was
involved in research on pure and doped TiO2, In2O3 and ZnO surface chemistry as well as gas-
29
metal oxide semiconductor surface interaction chemistry and followed seminars and public
lectures in Crete University as well as short training in SEM and AFM thin film
characterization in Laboratories in FORTH. His work experience gained working in PMP
Project will materialize in two papers, which are in preparation. Bernard Piechal, from
Warsaw University, joined the Grenoble team. He has received a PMP support of 3 months
from May 1, 2006 to July 31, 2006. During his stay, he receives a training in cathodoluminescence to carry out a Cathodo- luminescence study of ZnO nanorods
C.3 Factual Information on the Young Researchers
For each young researcher appointed with network funds, provide the following
information in tabular form: name, nationality, age at time of appointment, start and
likely end date of appointment, category of researcher (post-doc, pre-doc mentioning
if undertaking PhD studies), scientific speciality, place of work, country of work, and
whether the researcher had previously worked or studied at another network partner.
Currently, there are two female young researchers in the PMP Network: Dr Zeila Zanolli
(Lund team) and Ms Mirela Suchea (Crete team).
Dortmund team
Name
Nationality
Age at time of appointment
Work period in the network
Category of researcher
Scientific speciality
Place of work
Country of work
Whether the researcher had previously
worked or studied at another network partner
Nicolas Le Thomas
French
28
December 2002 – December 2004
Post-doc
Optoelectronics
Dortmund Universität
Germany
PhD in Grenoble Team
Name
Nationality
Age at time of appointment
Work period in the network
Category of researcher
Scientific speciality
Place of work
Country of work
Whether the researcher had previously
worked or studied at another network partner
Marco Allione
Italy
27
April 2005 – March 2006
Post-doc
Optoelectronics, Nonlinear Optics
Dortmund Universität
Germany
no
30
Name
Nationality
Age at time of appointment
Work period in the network
Category of researcher
Scientific speciality
Place of work
Country of work
Whether the researcher had previously
worked or studied at another network partner
Jordi Gomes
Spain
25
May 2006 – July 2006
Pre-doc
Optoelectronics, Nonlinear Optics
Dortmund Universität
Germany
No
Grenoble team
Name
Nationality
Age at time of appointment
Work period in the network
Category of researcher
Scientific speciality
Place of work
Country of work
Whether the researcher had previously
worked or studied at another network partner
Name
Nationality
Age at time of appointment
Work period in the network
Category of researcher
Scientific speciality
Place of work
Country of work
Whether the researcher had previously
worked or studied at another network partner
Name
Nationality
Age at time of appointment
Work period in the network
Category of researcher
Scientific speciality
Place of work
Country of work
Whether the researcher had previously
worked or studied at another network partner
Jacek Kasprzak
Polish
24
01.10.2003-30.09.2006
Pre-doc
Optics and physics of semiconductor
nanostructures
Laboratorie de Spectrometrie Physique
Grenoble
France
No
Andrea Balocchi
Italian
29
1 March 2003 - 29 February 2004
Post-doc
Spectroscopy and dielectric material
deposition
University Joseph Fourier, Grenoble
France
Never worked in a network before
Bernard Piechal
Polish
1 May 2006 – 31 July 2006
Pre-doc
Cathodoluminescence study of ZnO
nanorods
University Joseph Fourier, Grenoble
France
Never worked in a network before
31
Cardiff team
Name
Nationality
Age at time of appointment
Work period in the network
Category of researcher
Scientific speciality
Place of work
Country of work
Whether the researcher had previously
worked or studied at another network partner
Name
Nationality
Age at time of appointment
Work period in the network
Category of researcher
Scientific speciality
Place of work
Country of work
Whether the researcher had previously
worked or studied at another network partner
Celestino Creatore
Italian
26
01 February 2003-01 February 2006
Pre-doc
Physicist
School of Physics and Astronomy, Cardiff
University, Cardiff, Wales
United Kingdom
No
Nikolay Nikolaev
Bulgarian
33
15 January 2003 – 15 July 2005
Post-doc
Physicist
School of Physics and Astronomy, Cardiff
University, Cardiff, Wales
United Kingdom
No. I had only individual Marie Curie
fellowship – contract HPMF-CT-2000-00499
Cambridge team
Name
Nationality
Age at time of appointment
Work period in the network
Category of researcher
Scientific speciality
Place of work
Country of work
Whether the researcher had previously
worked or studied at another network partner
Simon Kos
Czech
32
29 June 2004- 28 June 2006
Post-doc
condensed matter theory
Cambridge University
UK
never worked in an EU network.
32
Name
Nationality
Age at time of appointment
Work period in the network
Category of researcher
Scientific speciality
Place of work
Country of work
Whether the researcher had previously
worked or studied at another network partner
Pablo Lopez Rios
Spanish
24
1 October 2003 –30 September 2006
pre-doc
Physicist
Cavendish Laboratory, Cambridge
UK
No
Lund team
Name
Nationality
Age at time of appointment
Work period in the network
Category of researcher
Scientific speciality
Place of work
Country of work
Whether the researcher had previously
worked or studied at another network partner
Zeila Zanolli
Italian
29
15 March 2004 – end of the Network
Post-doc
quantum optics, nanostructures
Lund
Sweden
No
Crete team
Name
Mirela Petruţa Şuchea
Nationality
Age at time of appointment
Work period in the network
Romanian
29
1-st of Aug 2002-31Dec2002; 1-st of June
2003-present
Pre-doc
Physics
Institute of Electronic Structure and Laser,
Foundation for Research & TechnologyHellas, PO Box 1527, Vasilika Vouton,
71110 Heraklion, Crete
Greece
In the period January-June 2003 I worked in
the “PICNIC” Project with the same location,
Institute of Electronic Structure and Laser,
Foundation for Research & TechnologyHellas, PO Box 1527, Vasilika Vouton,
71110 Heraklion, Crete, Greece.
Category of researcher
Scientific speciality
Place of work
Country of work
Whether the researcher had previously
worked or studied at another network partner
33
Name
Nationality
Age at time of appointment
Work period in the network
Category of researcher
Scientific speciality
Place of work
Country of work
Whether the researcher had previously
worked or studied at another network partner
Ioan Valentin Tudose
Romanian
26
1-st of Ianuary 2006-30 June 2006;
Pre-doc
Chemistry
Institute of Electronic Structure and Laser,
Foundation for Research & TechnologyHellas, PO Box 1527, Vasilika Vouton,
71110 Heraklion, Crete
Greece
No
Paderborn team
Name
Nationality
Age at time of appointment
Work period in the network
Category of researcher
Scientific speciality
Place of work
Country of work
Whether the researcher had previously
worked or studied at another network partner
Nicolas Rousseau
French
29
12-01-04 - 12-01-05
Post-Doc
Molecular beam epitaxy
Low scale Surface Analysis
Paderborn
Germany
Work within the Renibel EU network
But with allocation from the French state
PART D - SKETCHES OF THE YOUNG RESEARCHERS
D.1
For each of the young researchers who will present their experiences at the Mid-Term
Review Meeting, provide a maximum 25 line description of the young researcher’s
scientific background, of his responsibilities in the network and of his experiences
(positive and negative) to date. These sketches should be written by the young
researchers themselves.
Dortmund team
Dr. Nicolas Le Thomas
Before to starting as a post-doc in the PMP network, I made a PhD about the design,
the processing and the optical characterization of semiconductor tunable laser diodes. It was
an applied subject. My scientific background relies mainly on simple optical spectroscopy
experiments (photoluminescence, electroluminescence, photocurrent, and absorption) and
semiconductor device modelling.
34
During my post-doc in the PMP network, I have been carrying out an experimental
work in the experimental physic group of professor Woggon in Dortmund, Germany. This
work gives me the possibility to extend my fields of expertise to advanced optical
spectroscopy measurements like micro-photoluminescence and time resolved imaging. The
project topic is the study of the coupling between CdSe/ZnS nanocrystals and electromagnetic
modes of spherical micro-cavities. The main motivation is the observation of the strong
coupling regime between a confined electron-hole pair and a photonic mode (photonic
dot/quantum dot coupling).
It is very exciting for me to work in an international laboratory such as the one in
Dortmund. I strongly believe that my competencies have increased a lot. The job fits very
well with what I expected at the beginning of this post-doc. I also enjoy a lot the PMP network
meetings which give the opportunity to present and discuss preliminary results. Moreover
these meetings contributed to develop ideas and to build up fruitful collaborations with other
experimentalist members of the PMP network, as for instance with the Lund team, in order to
make challenging experiments. The main difficulty to carry out such experiments was my
limited contract time.
Dr. Marco Allione
The activity carried on in the Group of Prof. Woggon in the Department of Physics of the
Dortmund University can be divided in two main part.
The first one concerned the spectroscopy of single quantum rods at low temperature.
Chemically synthesized CdSe/ZnS core/shell quantum rods have been investigated in a microphotoluminescence setup previously realized there, that make use of a bath cryostat with a
microscope objective mounted on a piezoelectrically driven stage placed inside. This allowed
to reach low temperature down to few K. Luminescence spectra of several isolated rods were
collected. Particular interest was paid to the polarization properties of their emission as well
as to its dependence on the polarization of the exciting source and on its intensity. Collected
spectra were then analyzed in order to attribute the different features observed to different
types of excitations. Evidences were found of the presence of excitons and of charged
excitons in some of the observed spectra of single rods at low temperature.
The second part of the activity was related to the study of surface plasmons propagation in
metal nanowires. Silver nanowires prepared from chemical synthesis (100 to 500 nm thick and
from few to few tens of microns long) were used for these experiments. Once cast on a glass
substrate they have been employed in an experimental setup for surface plasmons excitation in
the so called Kreschmann-Raether configuration, which makes use of light totally reflected at
the glass/air interface. Different types of light sources were used at this purpose.
In summary both activities were extremely useful for me to practice on space resolved
spectroscopy techniques at room and at low temperature and to improve my knowledge on
physics of low dimensional semiconductor and metal structures as well.
Mr. Jordi Gomis Brescó
From the first of May to the end of July, I, Jordi Gomis Brescó, stayed in the experimental
physics eIIb group from the Universität Dortmund. During that period of time I have been
35
trained in the use of spectroscopic techniques for optical characterization of nanostructures,
including spatial and temporal high resolution techniques as confocal measurements and,
mainly, heterodyne pump and probe measurements that allow time accuracy in the range of 100
fs, limited only by the temporal broadness of the laser pulse employed in the measurement. In
such a set up, a titan-sapphire laser is used to pump an Optical Parametric Oscillator, allowing
us to cover a big spectral range (from 700-1000 nm the titan-sapphire laser alone and from
1050-1300 nm with the use of the OPO). The alignment and optimal use of both devices
formed part of the training procedure. Other less relevant techniques, like optical
autocorrelation with a separated autocorrelator and cross correlation through the heterodyne
setup were also used. The need of cryogenic temperatures lead me to get the proper preparation
to deal with liquid nitrogen and helium, and be capable of using properly the evaporated helium
recovery line present in the university.
Grenoble team
Mr. Jacek Kasprzak
I am at the first year of my PhD work in Laboratorie de Spéctrométrie Physique in
Grenoble at Joseph Fourier University. I work under supervision of Dr. Le Si Dang. Our team
is involved in Photon Mediated Phenomena European Research Network. Personally, I take a
part in it as the young researcher, and my work is supported by the means of this program. I'd
like to present some of my experience of being a network member. I have three kinds of
general remarks concerning:
- Scientific contribution of the network,
- Quotidian work in laboratory and live in Grenoble
- Financial support.
SCIENTIFIC CONTRIBUTION
The subject of my work is polariton phenomena in microcavities. Being the network
member gives me the unique chance to present my scientific results at network's meetings at
much larger circle then the laboratory. At the same time the regularity of workshops forces me
to recapitulate my results and trains my ability of presentation. The meetings give me fantastic
occasions to meet European scientific community working on the similar subjects: discuss
with experts and other young researchers as well, in informal atmosphere. On the other hand
the network meetings sketch the overview of actual state of work on photon mediated
phenomena in semiconductors on European arena. The meetings give also opportunity to visit
external scientific centres.
LIVE IN GRENOBLE and WORK IN LABORATORY
Decision of starting the PhD work in Grenoble opened a new chapter in my life.
Beside of obvious scientific reasons I was appealed by the beauty of the whole Grenoble
region. Living in Grenoble give me unrepeatable chance to develop my hobbies: mountain
trekking and skiing.
I have a pleasure to work in Laboratory de Spéctrométrie Physique: laboratory with good
tradition and great ambiance. I experience atmosphere of "taking care of the others" every day.
Among many colleges, I have met here a few people, whom now I consider as the friends. I
could find here the people who helped me - as a foreigner who knew neither the language nor
36
administration – with all: starting from inscription to the university and tons of administration
papers, ending at renting the apartment. I appreciate also the conditions I was employed: I
have the work contract with Joseph Fourier University and I'm PhD student at the same time
(with all the students rights). As a member of "équipe mixte UJF-CEA-CNRS” I have a
possibility to cooperate with strong grenoblan scientific community.
FINANCIAL SUPPORT
The financial support I am given is enough to live in Grenoble, even if these are the
means for me and my wife. I find it very good that there are the money to cover my journey to
Poland - my homeland, once a year. I am also grateful for paying for me two months of French
courses.
Mr. Jacek Kasprzak (last report)
From 1st of October 2003 to 9th of July 2006 I had the chance to be a member of the
Photon-Mediated-Phenomena (PMP) European Research Network. I worked as a “young
researcher” in the Grenoble team, and the PMP financial support allowed me to perform PhD
studies at the Joseph Fourier University in Grenoble. My experimental training in Laboratoire
de Spectrométrie Physique was focused on the research for Bose condensation in solid state
systems, in particular in semiconductor microcavities.
Being member of the network gave me the unique opportunity to present our results
on the European arena and exchange ideas with experts on semiconductor physics and
photonics, and other young researchers during network’s workshops. I am convinced that
those regular meetings (in Cambridge, Lund, Autrans, Paderborn, Dortmund, Cardiff and
Crete) were extremely useful. Not only that they motivated to recapitulate, summarize and
properly present our results, but also they allowed to follow the progress made by other teams
working on photon mediated phenomena is semiconductors. Thanks to these workshops I
could visit other European scientific poles and meet the people working there.
The network gave me an opportunity to go beyond the scientific community of my
team, laboratory and university and start cooperation on the European scale. This proves to be
very efficient since throughout joint efforts of teams led by Le Si Dang (Grenoble), B.
Deveaud (Laussane), P. Littlewood (Cambridge) we succeeded in demonstrating that Bose
condensation can occur in semiconductor microcavities.
I acknowledge this network for covering my frequent travel costs required for this
project, as well as the conference expenses (Warsaw 2005, Jaszowiec 2006). I also appreciate
the possibility of reimbursement of flights to Warsaw (my hometown), of tuition fees at the
university and of French language courses (~60h).
At the same time, I think that the mobility condition, so important for the European
Community, should be facilitated for members moving with their families. The practical
solutions would be, for example, the possibility of covering travel expenses and language
courses for the whole family.
Dr. Andrea Balocchi
Before the appointment I completed a PhD at the Physics department at Heriot-Watt
University, Edinburgh, Scotland. The subject of the research has been the development of a
37
fibre-based tunable semiconductor VCSEL for and telecommunications spectroscopic
purposes. The research has mainly involved the design and actual realisation of the device and
its subsequent characterisation. In addition, the PhD research has involved the spectroscopic
characterisation of wide band-gap II-Vi materials (ZnSe, ZnS, MgS, MgSe and alloys) grown
in the group for the realisation of room-temperature strongly coupled devices.
The work during the year as network post-doc has involved the design and realisation of
highly reflecting dielectric Bragg mirror for visible and UV strongly coupled microcavities.
The work has included the investigation of the suitable materials for the wavelength of
interest and the most appropriate method of deposition for the minimisation of absorption and
material roughness.
During the year I have also contributed in the spectroscopic research on the materials and
structure developed in the group and in particular on the cathode-luminescence of wide bandgap materials such as ZnO and GaN.
The position as network post-doc has allowed me on one side to broaden my spectroscopic
knowledge. I have learned new technique and methods of optical investigation of
semiconductors. In addition the use of different instrumentation has widen my technical
experience in this domain.
Moreover, the work on the dielectric material deposition has allowed exploring and varying
my knowledge towards field on which during my PhD I was only indirectly involved.
The network has allowed me to exchange experiences and knowledge especially with
the group of Paderborn.
During my appointment as network post-doc I participated to two network organized
meetings:
1st March 2003 in Cardiff:
“ZnCdSe/ZnSe strongly coupled microcavities”
2nd October 2004 in Crete:
“Oxide mirrors for blue and infrared microcavities”
Mr. Bernard Piechal
I was a member of the Photon-Mediated-Phenomena (PMP) European Research
Network from 1st of May to 31st of July 2006. I was working as a “Young Researcher” at the
Laboratoire de Spectrométrie Physique, Joseph Fourier University in Grenoble, in the
workgroup led by Daniel Le Si Dang. My work was focused on the cathodoluminescence
studies of ZnO nanorods.
Paricipating in the PMP network was very profitable for me. It gave me the
opportunity to take part into such a new and dynamically expanding field of research, as the
semiconductor nanorod and nanowire studies. Moreover, during the stay in Grenoble I have
learned new experimental techniques, especially scanning electron microscopy and
cathodoluminescence. These techniques are widely used, so I am convinced that learning them
surely will be very fruitful in my future research work. I have also learned various techniques
to prepare single nanorod samples.
During the period I worked in Grenoble I participated in the PMP workshop in
Cambridge. I found it very interesting, as the talks presented there were much more detailed in
comparison to the talks that are usually presented at conferences. Additionally the workshop
allowed me to meet researchers from outside the community of my home university and to
establish my own international contacts, the first ones in my career.
38
Cardiff team
Mr. Celestino Creatore
I graduated in Italy in October 2002. I got my degree after a four years study course
and a one-year project. My research concerned the application of unsupervised-learning
algorithms (derived in a statistical mechanics framework) applied to magnetoencephalographic signals. The research was developed within the Theory Group of the
Physics Department and the neuroscientists of the “FateBeneFratelli” Hospital in Rome.
Since February 2003 I am a Young Researcher Ph.D. student within the “Photon
Mediated Phenomena Network” project and I work at the Department of Physics and
Astronomy in Cardiff University, under the supervision of Prof. Ivanov.
My present research investigates the interaction between photons and Quantum Dots. Briefly,
it is a theoretical work (both analytics and numeric have being developed) which in the near
future will be developed in collaboration with other researchers joining the Network, in
particular, the group of Dr. Pistol (Lund Team, Sweden) for experimental work and the group
of Prof. Littlewood (Cambridge Team, U.K) for theory.
As a young researcher within the Network I think that the importance of the meetings
with the other members is huge and it enriches the Ph.D. work: it is a great opportunity to
have a useful exchange of ideas in a friendly and informal atmosphere. Besides the scientific
work, I have been involved in the organization of the first meeting of the network (held in
Cardiff on April 2003) and the technical preparation of the proceedings.
Besides the Network meetings, I have attended and presented a poster at the
“International Summer School on Functional Nanostructures” (Karlsruhe, Germany) on
September 2003, attended and had an oral presentation at the International Conference “SIOE,
Semiconductor and Integrated OptoElectronics” (Cardiff, Wales) on April 2004, attended
(with a fellowship) the “2004 Lectures in Chemistry and Physics: The Nanotechnology
Revolution” organized by the “Onassis Foundation” in Greece on July 2004.
Mr. Celestino Creatore (last report)
During my last year as young researcher in Cardiff (under the supervision of Prof. Ivanov), I
theoretically studied the role of damping in the interaction between photons and excitons in
Quantum Well structures. We developed both a semi-classical and a microscopic-Hamiltonian
formalism. We found interesting and novel results that have been reported in the International
Conference “Nonlinear Optics and Excitation in Semiconductors NOEKS8”, held in
Muenster, Germany (20-24 Febraury 2006) and in the last Network Workshop held in
Cambridge (23-25 June 2006) and have been published in the journals “Physica Status Solidi
c” (vol. 3, No. 7, pp. 2444-2448) and “Journal of Physics: Condensed matter” (in print). This
project gave me the possibility to enhance my knowledge in the nowadays very important
field of light-matter interaction in confined structures and to develop skills in numerical
computing to solve physical problems. The attendance of the Network Workshops was
extremely useful since I met important scientists and had with them stimulant and useful
discussions.
Within the Network I also worked as a webmaster for the Network website and I was involved
in the organisation of the first network workshop, held in Gregynog, Wales, (28-31 March
2003) and in the editing of the special issue of “Journal of Physics: Condensed matter” that
collects all the Workshop’s contributions.
39
Dr. Nikolay Nikolaev
My name is Nikolay I. Nikolaev. I was born in Svishtov, Bulgaria, in 1970. I received
my MSc degree in 1993 in the Department of Quantum Electronics and Laser Physics of Sofia
University. In 1999 he received his Ph.D. degree in the area of electromagnetic wave
propagation at the Department of General Physics of Sofia University. From 1997 through to
2000 I worked as researcher and scientific collaborator in Institute of Electronics, Bulgarian
Academy of Science. From 2000 through to 2001 as a assistant professor in the Department
of Physics, University of Architecture, Civil Engineering and Geodesy in Sofia. From 2001
through to 2003 I worked as a PostDoc researcher at Fraunhofer IISB in Erlangen, Germany
under Marie Curie Individual Fellowship. On 15.01.2003 I became a member of PhotonMediated Phenomena Network and I started work as a research associate in the Department of
Physics and Astronomy of Cardiff University in Wales, UK. My previous research experience
and interests - investigating and modelling of wave propagation in different media –
gyrotropic plasma, nano-semiconductor structures fit well to the research activities of the
network. I have a desire to mention the benefits for me as a member of network:
-Due to the financial support of the network I can continue evolving of my research career.
For me is also important that I work here in Cardiff among many highly qualified scientists in
the Physics department. Attending of various seminars (some of them funded by network) is
useful for me.
-Financial support of the network for buying necessary for science computer systems,
software, books.
-The benefit for me is supervision of my work from Prof. Ivanov. The often scientific
discussions with him and his big scientific experience and scientific contacts with many
outstanding scientists are great help for me.
-Another advantage of being member of network is the possibility for the scientific contacts
between our group here in Cardiff and another teams from our Network. The scientific
meetings (Gregynog, Crete, Cardiff), information exchange via Internet, telephone provide
good base for improvement of my scientific work.
For my stay here I have one article which will be published very soon in Journal of Physics:
Condensed Matter. Now I am preparing a next paper. We plan to submit it to Phys. Rev. B.
-I took part in preparation of scientific meeting in Gregynog.
-I took part in preparation of the special issue of Journal of Physics: Condensed Matter
containing the Proceedings of the First Workshop of the Network in Gregynog.
-I work as a second supervisor of the PhD student Andrew Smith.
Dr. Nikolay Nikolaev (last report)
My name is Nikolay I. Nikolaev. I was born in Svishtov, Bulgaria, in 1970. I received
my MSc degree in 1993 in the Department of Quantum Electronics and Laser Physics of Sofia
University. In 1999 he received his Ph.D. degree in the area of electromagnetic wave
propagation at the Department of General Physics of Sofia University. From 1997 through to
2000 I worked as researcher and scientific collaborator in Institute of Electronics, Bulgarian
Academy of Science. From 2000 through to 2001 as a assistant professor in the Department
40
of Physics, University of Architecture, Civil Engineering and Geodesy in Sofia. From 2001
through to 2003 I worked as a PostDoc researcher at Fraunhofer IISB in Erlangen, Germany
under Marie Curie Individual Fellowship.
In 2003 I joined Cardiff University as Research Associate at Prof. Alex Ivanov’s
Optoelectronics Theory Group (Cardiff School of Physics and Astronomy), supported through
the EU PMP Network. Here, I used different methods to investigate polariton optics. First - I
applied the WG method to calculate exciton-resonance-mediated light scattering from
photonic semiconductor structures - spheres, rods, ellipsoid structures [c1]. Second - I used
analytical method, based on solving of system from Maxwell’s equations for light field and
Hopfield’s equation for polarization [1,2]. In his work coherent optics of dipole-active,
dispersionless excitons in spherical semiconductor photonic dots (PDs) is developed. It is
shown that both strong and weak coupling regimes can intrinsically be realized simply by
changing the parameters of the dot and surrounding medium. Third - I used [3,4] Green
function technique to calculate Bragg scattering of polaritons by a coherent acoustic wave,
mediated and strongly enhanced by the exciton states resonant with the acoustic and optic
fields in the intraband and interband transitions, respectively. In this case, in contrast with
conventional acousto-optics, the resonantly enhanced Bragg spectra reveal the multiple orders
of diffracted light. The predicted phenomena are very interesting and experiments to observe
them have to be conducted.
My work in Network was appreciated by Cardiff University and from May through to
December 2005 I was invited to join a cross-disciplinary project of Cardiff School of
Biosciences on high-throughput screening. I was appointed as Research Associate in the
Molecular Cell Biology Research Group, where in collaboration with Dr. Paola Borri I made
numerical and analytical simulations for a novel approach to high-throughput biochemistry. In
particular I implemented the Metropolis Monte Carlo method to model the conformational
behaviour of long DNA molecules. This very useful for me experience won’t be possible
without my initial support from PMP Network.
At the end I would like to mention the benefits for me as a member of network:
-my satisfaction that my previous research experience and interests - investigating and
modelling of wave propagation in different media – gyrotropic plasma, nano-semiconductor
structures fit well to the research activities of the network.
-Due to the financial support of the network I can continue evolving of my research career.
For me is also important that I work here in Cardiff among many highly qualified scientists in
the Physics department. Attending of various seminars (some of them funded by network) is
useful for me.
-Financial support of the network for buying necessary for science computer systems,
software, books.
-The benefit for me is supervision of my work from Prof. Ivanov. The often scientific
discussions with him and his big scientific experience and scientific contacts with many
outstanding scientists are great help for me.
-Another advantage of being member of network is the possibility for the scientific contacts
between our group here in Cardiff and another teams from our Network. The scientific
meetings (Gregynog, Crete, Cardiff, Paderborn, Dortmund), information exchange via
Internet, telephone provide good base for improvement of my scientific work.
-I took part in preparation of scientific meeting in Gregynog.
-I took part in preparation of the special issue of Journal of Physics: Condensed Matter
containing the Proceedings of the First Workshop of the Network in Gregynog.
-I work as a second supervisor of the PhD student Andrew Smith.
41
1. N I Nikolaev, A Smith and A L Ivanov, "Polariton optics of semiconductor photonic dots:
weak and strong coupling limits", J. Phys.: Condens. Matter 16 (2004) S3703-S3719
2. A Smith, N I Nikolaev and A L Ivanov, "Coherent optics of spherical photonic dots:
transition between weak and strong coupling" Proceedings of the 27th International
Conference on the Physics of Semiconductors 26th-30th July 2004 Flagstaff, Arizona, USA,
edited by J. Menendez and C. Van de Walle, AIP Conference Proceedings Vol 772, AIP,
Melvile, NY, 757-758 (2005).
3. K. Cho, K. Okumoto, N.I. Nikolaev and A.L. Ivanov, "Bragg diffraction of microcavity
polaritons by a surface acoustic wave" Phys. Rev. Lett. 94, (2005) 226406 [Errata: Phys. Rev.
Lett. 94, (2005) 239905(E)].
4. A. L. Ivanov, N. I. Nikolaev, and K. Cho, SAW-driven microcavities for device
applications, IEE Proceedings Optoelectronics, in print (2006).
Participations in conferences
c1. A Smith, N I Nikolaev and A L Ivanov, "Polariton optics of spheroidal and cylindrical
single-mode microcavities" Semiconductor and Integrated Optoelectronics Conference
(SIOE), 14th-16th April 2003, Cardiff, Wales, UK (oral presentation),
c2. A Smith, N I Nikolaev and A L Ivanov, "Coherent polariton optics of spherical photonic
dots: weak and strong interaction limits", Postgraduate Research Conference in Electronics,
Photonics, Communications & Networks, and Computing Science. University of
Hertfordshire 5th to 7th April 2004, Hatfield, UK (oral presentation)
c3. A Smith, N I Nikolaev and A L Ivanov , "Polariton optics of semiconductor photonic dots:
weak and strong coupling limits", 27th International Conference on the Physics of
Semiconductors 26th-30th July 2004 Flagstaff, Arizona, USA (poster presentation)
c4. A Smith, N I Nikolaev and A L Ivanov , "Transition between the weak and strong
polariton coupling regimes in spherical photonic dots" 16th meeting of Quantum Electronics
and Photonics Group (QEP-16), 6th- 9th September 2004, Glasgow, UK (poster presentation)
c5. K.Cho, K. Okumoto, N.Nikolaev & A. L.Ivanov, "Bragg scattering of microcavity
polaritons by Surface Acoustic Wave", 9th Conference on the Optics of Excitons in Confined
Systems (OECS9) Southampton (UK), Sept 5-9 (2005).
Cambridge team
Dr. Simon Kos
As a PhD student at the University of Illinois in Urbana, I worked on various problems
in superconductivity using the quasiclassical approximation both in the Andreev and in the
Eilenberger formalism. As a postdoc in Los Alamos, NM, I first studied the Ce-based 115
heavy-fermion materials, thus joining a major experiment-theory effort there at that time.
42
Specifically, I helped analyze the NMR and specific-heat data on the material to show that
they both suggested a two-component description of the material. I then worked on energy
transfer between quantum-well and quantum-dot excitations, and on spin dynamics, both
involving inorganic semiconductors. In Cambridge, I would like to extend these last studies
into conjugated organic materials. I am new to Cambridge as well as to the Network; I expect
to learn about my responsibilities in the network at the Meeting.
Dr. Simon Kos (last report)
In the course of last year, I mainly continued working on the study of spin dynamics in lightly
n-doped GaAs. This is a joint experiment-theory project. The experimental techniques used
are optical injection and detection, which have a close relation to the PMP network. Our main
result was the development of a system of drift-diffusion equations that quantitatively describe
spin dynamics in GaAs epilayers. Our focus was on the study of the effect of symmetrylowering strain on spin dynamics. Due to spin-orbit coupling, this strain acts as a momentumdependent Zeeman field, and hence can be used to rotate the spin polarization. Its
momentum dependence has the additional benefit of increasing the spin transport length
compared to the case when magnetization is rotated by an applied magnetic field.
I have also been working on the theory of spin noise in systems with moving spin-carrying
particles, both conduction electrons in semiconductors and gases of alkali atoms. Generally,
with the decreasing size of systems under study, noise in the measurement grows relatively to
the signal or even in absolute value. We can turn the problem into a tool and use noise to
study the response functions of a system by appealing to the fluctuation-dissipation theorem. I
have been focusing on the signatures of different transport regimes as manifest in the
noise signal.
I have also continued working on spin and charge dynamics in the manganites, again
connected to imaging experiments. We have used strain to understand the nature of the
charge-ordered state in a manganite film. Since under the application of strain, the chargeorder superlattice moved differently from the parent crystal lattice, we concluded that the two
are only weakly coupled, contrary to the established models of the manganites, in which the
charge ordering is described as alternating valence of the manganese or oxygen atoms. We
have also been studying polaron dynamics in bilayer manganites that gives rise to behavior
similar to quasiparticles in high-temperature superconductors. The experimental technique
here is optical again, namely the angle-resolved photoemission spectroscopy.
Publications:
M. Hruska, S. Kos, S.A. Crooker, A. Saxena, and D.L. Smith, Effects of strain, electric, and
magnetic fields on lateral electron spin transport in semiconductor epilayers, Phys. Rev. B 73,
075306 (2006).
S. Cox, E. Rosten, J. C. Chapman, S. Kos, M. J. Calderon, D. J. Kang, P. B. Littlewood, P. A.
Midgley, N. D. Mathur, Strain control of superlattice implies weak charge-lattice coupling in
La0.5Ca0.5MnO3, Phys. Rev. B 73, 132401 (2006).
P. B. Littlewood and S. Kos,
43
Focus on the Fermi surface, Nature News and Views 438, 435 (2005).
Network meetings:
Closing meeting of the PMP network, Cambridge, June 2006, talk title:
"Spins under strain"
Conferences attended:
2006 APS March Meeting, talk title: "Spin noise of itinerant fermions"
Third meeting of the EU project "Controlling Mesoscopic Phase Separation", Paris, June
2006, talk title: "Weak coupling of the charge order to the lattice in La1-xCaxMnO3 close to
x= 0.5".
Quantum Complexities in Condensed Matter, Cambridge, July 2006, talk title: "Spins under
strain".
Invited talks:
Florida State University, Tallahassee, Florida, USA, March 2006, talk title: "Spins under
strain".
University of California, Santa Barbara, California, USA, March 2006, talk title: "Spins under
strain"
University College London, May 2006, talk title: "Spins under strain".
Mr. Pablo López Ríos
The problem in which I have started to work is finding the theoretical phase diagram
of the homogeneous electron-hole system, which is a model for semiconductors described by
a small number of parameters. Knowledge of the theoretical properties of the system for given
values of these parameters shall serve as a guide for experimentalists and engineers in their
use and development of materials and devices.
The numerical tool of choice in this area is the Quantum Monte Carlo (QMC) method,
as it has been proven capable of performing many-body integrals without omitting correlation
effects, thus yielding the most accurate results currently available. Cambridge QMC code is
called Casino, which aims at being a completely general, flexible package capable of treating
systems ranging from atoms to complex molecules and solids, using some of the best-known
QMC methods: Variational Monte Carlo (VMC), correlated-sampling Variance Minimization
(VM) for VMC wave-function optimization, and fixed-node Diffusion Monte Carlo (DMC),
which is extremely powerful.
In this first year of my PhD studies, I've become familiar with the QMC method as
well as with the Casino program. Some of the contributions I've made to this project so far
are: inclusion of an automatic time step optimization algorithm for VMC; correlation-time
calculation routines; optimization of existing VM algorithms, achieving performance
increases of up to 300%; a small number of contributions to the package's script library, and
44
general debugging. For the specific case of electron-hole systems, we have developed a new
functional form of the wave-function that we hope shall shed light on some inconsistencies
found in previous theoretical studies of the phase diagram. This has also been implemented in
Casino, and the preliminary results obtained for the two-dimensional electron-hole bilayer one of the systems of interest- do look promising.
There is still work to be done in order to draw a well-characterized phase diagram of
the electron-hole system, but it seems to me that the basis is now set and accurate results will
follow in a short time.
Mr. Pablo López Ríos (last report)
The aim of my PhD is to obtain an accurate phase diagram of the electron-hole system -- a
model of excited semiconductors – by means of Quantum Monte Carlo (QMC) techniques.
Other groups have already performed QMC calculations of electron-hole systems, but higher
accuracy can be obtained if the QMC method is developed further. Hence, this year has been
spent perfecting and using the following novel techniques:
* Backflow. Backflow is capable of generating very accurate trial wave-functions due to its
ability to modify the wave-function nodes, hence being able to correct for the Fixed-Node
Approximation (FNA), the only uncontrolled approximation that is present in the diffusion
Monte Carlo method. It should be noticed that backflow has never been applied to electronhole systems before.
* A more general, robust approach to studying phase diagrams using QMC, which involves
using a single flexible wave function to describe the system and then determine the phase by
means of analyzing QMC expectation values such as the condensate fraction, as opposed to
the widely-used technique of associating different single-particle orbitals to different phases,
an approach which is likely to fail when sophisticated trial wave functions (such as backflowSlater-Jastrow wave functions) are used.
List of publications
- P. Lopez Rios, A. Ma, N.D. Drummond, M.D. Towler, and R.J. Needs, “Inhomogeneous
backflow transformations in quantum Monte Carlo”, in press, Phys. Rev. E (2006).
- N.D. Drummond, P. Lopez Rios, A. Ma, J.R. Trail, G.G. Spink, M.D. Towler, and R.J.
Needs, "Quantum Monte Carlo study of the Ne atom and the Ne+ ion", J. Chem. Phys. 124,
224104 (2006).
- Co-author of the current version of the CASINO quantum Monte Carlo software package:
R.J. Needs, M.D. Towler, N.D. Drummond and P. Lopez Rios, CASINO version 2.0 User
Manual, University of Cambridge, Cambridge (2005).
- PhD thesis, to be submitted in September 2006.
45
- A paper on backflow + electron-hole systems is in preparation.
List of conferences attended
- 'APS March meeting 2006', Baltimore, USA.
- 'Quantum Monte Carlo in the Apuan Alps II', TTI, Tuscany, Italy.
- Electronic structure winter workshop, Robinson College, Cambridge, UK.
- PMP network June 2006 meeting.
List of talks given
- 'The zero-variance limit in QMC' at the electronic structure discussion group, TCM group,
Cambridge, UK.
- 'Inhomogeneous backflow transformations in QMC' at the APS March meeting, Baltimore,
USA; and at the TTI, Tuscany, Italy.
- 'QMC study of electron-hole systems' at the PMP network June 2006 meeting, Cambridge,
UK.
List of posters presented:
- 'Inhomogeneous backflow transformations in QMC' at electronic structure, Winter
workshop, Robinson College, Cambridge, UK.
List of other activities:
- Lecturer and practical-session demonstrator at the 'QMC and the CASINO program' Summer
school, TTI, Tuscany, Italy.
Lund team
Dr. Zeila Zanolli
Scientific background:
I’ve conducted a PhD research activity on GaAs-based Quantum Cascade Lasers
(QCLs) and LEDs emitting in the midbased on inter-subband transitions in a multiple quantum well heterostructure, so their
emission wavelength can be chosen by design. The study was developed across the various
design issues (comparing different injector and active region schemes, designing new devices
and calculating the appropriate waveguide layers), the optimization of the fabrication
techniques and of the whole processing scheme of the lasers, and the optical and electrical
characterization of the devices. These measurements were performed at low temperature
(10K) using an FT-IR spectrometer operated both in step-scan and in rapid-scan mode.
I have theoretical experience in the QM study of the time evolution and decoherence
effects in two level systems due to the interactions with the external environment.
Responsibilities in the network and experiences (positive and negative):
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Our group is working to build a new setup for detecting infrared (1photoluminescence from quantum dots. We have planned to study InP and InAs quantum dots
embedded in (Ga)InP and (Al)GaAs quantum wires, respectively.
My activity was mainly devoted to writing a labVIEW program to control the whole
experimental setup. This program allows the control of the spectrograph (grating, wavelength
and entrance slit width selection), of the IR camera and of the DT3157 frame grabber for the
different image acquisition modes of the camera.
The image acquisition part of the program was the most challenging one, since at the
beginning even the DT sample programs were not working. Work was done to understand the
right settings of both camera and frame grabber to make them working together. Besides the
frame grabber was supposed from DT Company to be controlled via a Visual C++ program,
so the calling of the DT functions was made via the “Call Library Function” mode of
labVIEW.
Dr. Zeila Zanolli (last report)
The research activity performed by Dr. Zeila Zanolli within the PMP network is focused
on the optical properties of quantum dots (QDs) and semiconductor nanowires (NWs). This
study is conducted using both experimental (photoluminescence measurements) and
theoretical (ab initio calculations) methods of investigation.
The investigation of single QDs aims at the understanding of the quantum physical
processes underlying the behaviour of the QD itself. This understanding can be exploited, for
instance, in the study of the photon statistics in the emission from quantum dots leading to
applications in quantum cryptography, quantum computing, single photon emitters and new
quantum devices.
Semiconductor NWs have generated considerable interest in the scientific community both
for fundamental reasons and for their potential technological applications. Since the typical
NWs dimensions are 20 – 40 nm in diameter and 1 – 4 m in length, they give the opportunity
to investigate quantum effects and optical and electronic properties in one-dimensional
systems. Besides, heterostrustures can be grown along the wire axis allowing the formation of
quantum dots and superlattices, or a shell can be added to the bare wire to improve the
intensity of the optical emission from the core. Nanowires act as waveguides for both photons
and electrons, hence they can be exploited in nano-photonics and nano-electronics.
a) Experimental study: photo-luminescence measurements
The optical properties of nanowhiskers and Quantum Dots (QDs) have been investigated
via low-temperature (4K) micro-photoluminescence (-PL) spectroscopy on single particles
(wires/dots) in the near IR (600 nm – 2 m).
A new -PL set-up was built to allow measurements in the 900 nm – 2 m range. A
LABVIEW program for the control of the experiment was written and the optical apparatus
between the spectrograph and the detection camera was optimized. The system is now
working and it is the primary investigation tool for the study of single InAs-based nanowires.
The investigated NWs are InAs-InP and InP-CdS core-shell systems. Nanowire core
diameters were typicaly among 20 and 70 nm. The InP shell radius was usually varied among
10 and 30 nm, while the CdS capping was up to 10 nm thick. Attention was paid to the
emission from both the core and the shell materials and on the possibility of increasing the
luminescence intensity and tuning the emission energy by straining the core. It was observed
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that the InAs core emission can be tuned by varying the ratio of the shell thickness to the core
diameter [1]. Besides, evidences of quantum confinement effects (more pronounced in the 20
nm core wires) were found [2]. The experimental results were compared with theoretical
calculations based on 8-bands kp theory, performed by Prof. Mats-Erik Pistol. The study of
the InP-CdS wires is reported in [3].
Studies of InP single QDs [4], and InAs QD embedded into InAs or InP nanowires were
also performed.
b) Theoretical investigation: ab initio calculations within DFT and GWA
The NWs are raising new challenges: being created in the laboratory, they can have a
physical structure and properties different from the natural materials. A proper understanding
of these features can be further exploited to tailor the behaviour of the NWs according to
specific needs.
Specifically, the InAs-InP core-shell NWs have wurtzite crystal structure, while the
corresponding bulk materials can exist only in the zinc-blende phase. Since there are neither
measured bulk properties nor previous theoretical studies on such new materials, the choice of
an ab initio method is highly appropriate for their theoretical investigation. Indeed this
calculation method does not require any knowledge of the material parameters and allows one
to predict numerous material properties.
Hence, research activity on III-V materials in the wurtzite phase using ab initio methods of
calculation has been performed. The methods employed are based on Density Functional
Theory (DFT) in the Local Density Approximation (LDA) and/or in the Generalized Gradient
Approximation (GGA) using pseudo-potentials and plane waves (PW) or ProjectorAugmented Waves (PAW). This first-principles approach allows the computation of ground
state properties such as total energies, charge densities, densities of states (DOS), equilibrium
lattice constants and elastic properties. The software packages used in this investigation are
ABINIT and VASP.
All-electrons calculation at the DFT/LDA level were used (using the WIEN2K software)
for the structure optimization of the InAs in the wurtzite phase and for the calculation of the
band structure with and without the inclusion of the Spin-Orbit interaction [5]. The allelectron results were compared to the results of pseudopotential calculations [6].
Excited states properties as band-structures were computed using methods based on
Many-Body Perturbation Theory as the GW approximation. The traditional approach of
perturbatively adding the GW corrections to the LDA band structure cannot be applied to the
InAs case. Hence, two different procedures were used and compared. In the first approach, the
GW band structure was corrected for the pd repulsion. In the second case, the LDA
wavefunction were used to start a Screened-Exchange (SX) calculation. Then, the GW
corrections were calculated using the latter SX wavefunction and eigenenergies as zero:th
order of the perturbative expansion. This led to the first calculation of the band structures of
InAs and GaAs in the wurtzite phase [7].
The outlined theoretical research project is conducted in collaboration with Prof. Ulf von
Barth (Lund University, Solid State Theory).
Publications within the Network:
[1] Z. Zanolli, L.E. Fröberg, M.T. Björk, M-E Pistol, and L. Samuelson, Fabrication, optical
characterization and modeling of strained nanowires, Thin Solid Films (In Press, Available
online from 25 January 2006).
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[2] Z. Zanolli, M-E Pistol, L.E. Fröberg, and L. Samuelson, Quantum confinement effects in
InAs-InP core-shell nanowires, Journal of Physics: Condensed Matter (accepted).
[3] Z. Zanolli, B.A. Wacaser, W. Seifert, K. Deppert, and L. Samuelson, Core-shell InP-CdS
nanowires: fabrication and study, Journal of Physics: Condensed Matter (accepted).
[4] B.A. Wacaser, K.A. Dick, Z. Zanolli, K. Deppert, and L. Samuelson, Size-selected
compound semiconductor quantum dots by nanoparticle conversion, Manuscript (2006).
[5] Z. Zanolli and U. von Barth, All-electron study of InAs wurtzite: structural and electronic
properties, submitted to Phys. Rev. B (2006).
[6] Z. Zanolli and U. von Barth, InAs with wurtzite crystal structure: full-potential and
psedopotential ab-initio calculations, DFTEM2006, refereed conference proceedings, edited
by J. Luitz et al, p. 186 (2006).
[7] Z. Zanolli, J. Furthmüller, F. Fuchs, U. von Barth, and F. Bechstedt, GW band structure of
InAs and GaAs in the wurtzite phase, submitted to Phys. Rev. B (2006).
Crete team
Dr. Mirela Şuchea
Scientific background
I studied physics in Physics Faculty at the University of Bucharest (1991-1997) with
Biophysics Specialization in the 4th and 5th years of study. I am licensed in Physics–
Biophysics with the License work: “The Ultrasonography. An Application in the PressureVolume Relation Study of the Left Ventricle”(1999), Coordinating teacher: Lect. Dr. Puiu
Bălan. In 1999 I attended the lectures in Consultant School for medical equipment at Zepter
Romania, Bio-Vita Program. In 2001 I got E. U. attestation as Medical Consultant for
Bioptron A.G. Switzerland. Between April 2000 and July 2002 I was working like assistant
laboratory in RAMI-Dacia –Synthetically Diamond Factory, Bucharest Romania. From
September 2002-present I am also a masters student in the Microelectronics Department of
Crete University.
Work experience
My main training work consists of structural and morphological characterization of
surfaces by microscopy and in particular utilizing, optical, AFM and SEM as well as TEM and
XTEM. I have followed lectures and sort time practical work in XRD, spectroscopy (UV-VIS,
FTIR and photoluminescence), optical and electrical characterizations, Hall measurements,
and IC’s processing work at the Laboratories at FORTH.
Working as a young researcher in the Crete team I learned also thin films growth techniques
utilizing the conventional evaporation and dc magnetron sputtering techniques.
Mr V. Tudose
Scientific background
I studied chemistry in Chemistry Faculty at the University of Bucharest (1998 – 2002) with
Radiochemistry Specialization. I am licensed in Chemistry with the license thesis:
“Cooperative effects in solvent extraction of VI uranium salts using carboxylic acids and
aromatic heterocyclic basis as extracting agents” (2002), Coordinated by Prof. Dr. Corneliu
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Podina. I received my master degree in Physical-Chemistry and Applied Radiochemistry at the
University of Bucharest in 2004. Since 2004 I’ve started my doctoral studies in Chemistry
dept. at the same University. Between 1999 and 2000 I’ve followed also the undergraduate
program courses in Physics Faculty of University of Bucharest. After my Master studies until I
joined the Crete team, I’ve worked also as teaching assistant in Radiochemistry Laboratory of
Chemistry Faculty.
Work experience
I’ve joined Photon Mediated Phenomena Program in January 2006 working as a young
researcher in the PEML Group at IESL FORTH, Crete Greece.
My main training work consists of chemical synthesis and characterization of ZnO
nanostructured compounds for different applications. I’ve developed a chemical route for ZnO
nanostructures and thin films growth. I’ve gained experience on XRD characterization, optical
and spectroscopic techniques as well as surface characterization using SPM image processing.
I become familiar with dc magnetron sputtering and thermal evaporation thin films growth
techniques. Except ZnO, I’ve been involved in research on pure and doped TiO2, In2O3 and
ZnO surface chemistry as well as gas-metal oxide semiconductor surface interaction
chemistry. I have followed seminars and public lectures in Crete University as well as short
training in SEM and AFM thin film characterization in Laboratories in FORTH. My work
experience gained working in PMP Project will materialize in two papers, which are still in
draft, but they will become ready for publishing by the end of this year.
Partial results were already presented as oral presentation in »International Conference on
Coatings on Glass and Plastics« in June 18-22 in Dresden/Germany as “Pure and Nb2O5
doped TiO2 amorphous thin films grown by dc magnetron sputtering at room temperature:
surface and photoinduced hydrophilic conversion studies” by M. Suchea, S. Christoulakis,
I.V. Tudose, D. Vernardou, M.I. Lygeraki, S. H. Anastasiadis, N. Katsarakis and G.
Kiriakidis.
Some other partial results are going to be presented in the 1st TCO International Symposium
which will be held in Crete in October 2006 as the poster presentation with the title “ZnO thin
films surface properties correlation with conductivity changes under UV
photoreduction/ozone oxidation processes” by M. Suchea, S. Christoulakis, I.V. Tudose, P.
Horvath, T. Kitsopoulos and G. Kiriakidis.
Working in Crete team as a member of PMP network was very useful for my career not only
for giving me the chance to work with highly qualified people in a quite good infrastructure
but also for very good access to scientific publications and scientific contacts within and
outside IESL/FORTH.
Paderborn team
Dr. Nicolas Rousseau
I have joined the Photon mediated phenomena network as a post-doctoral the 12 of
January 2004. During the first time, I have been trained on various methods of semiconductor
50
characterizations. Specifically, I have acquire new understanding on high resolution X ray
diffraction, cathode-luminescence, reflection high energy electron diffraction, atomic force
spectroscopy, Energy Dispersive X-ray Analysis. Also, I have drastically improved my skills
in crystal growth techniques. I am now able to master the growth of GaAs layers,
heterostructures based on ZnSe, ZnMgSe, ZnCdSe, CdSe, and I equally get a strong knowhow
on the growth of Stranski-Krastanov CdSe quantum Dots. This knowledge will be now
helpful to realized planar microcavities with CdSe quantum well or stacked CdSe quantum
dots as active layers.
After this training period, I have start a work on Bragg mirror based on ZnSe and
ZnMgSe layers. My aim with this study, is to obtain an high reflectivity (above 90%) centered
on 520 nm, which is the exact wavelength of the active layer inside microcavities. Concerning
this work, I have already cross many steps. In order, the mastering of the magnesium content
inside the ZnSe layers, and also a perfect control of layers thicknesses, which is a crucial
parameter for positioning the stop band of the mirror. So this two first results allow us to
produce in a reproducible way Bragg-mirrors centered on 520 nm with a reflectivity of more
than 80%.
Now, my work will consist in improving the reflectivity to reach 90% and be able to realize a
microcavity with a backside Bragg mirror ZnMgSe/MgSe. I would like to add the fact that
this work is realized in cooperation of a PhD student (M.Arens) which works also on it.
PART E - NETWORK FINANCING
E.1
Compare, in tabular form, the expenditure to date of each network partner (an
estimate will be sufficient) with the allowable costs foreseen in the table following the
signatures in the contract. Also estimate a breakdown of the total expenditure to date
by the network into the cost categories A, B, C and D. Explain any substantial
differences from the rates of spending originally foreseen.
The PMP Network final expenditure will be directly reported to the EU Commission by the
RACD (Cardiff University) responsible for the Network budget: Mr Nick Bodycombe (Email:
[email protected]) and Mrs Cerys Phillips (Email: [email protected]).
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