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University of Ioannina
Department of Materials Science & Engineering
Computational Materials Science
Plasmonic Near-Field Enhanced
Absorption and Scattering
Elefterios Lidorikis
Materials Science & Engineering, University of Ioannina, Greece
June 8-11, 2011
Crete, Greece
Crete, 8-11 June 2011
Plasmonic Near-Field Enhanced Absorption and Scattering
Localized surface plasmon resonance
•  Inside an electric field a
nanoparticle gets polarized
•  Surface plasmon resonance
•  Strong scattering
•  Strong absorption
•  Strongly enhanced near fields
Plasmonic Near-Field Enhanced Absorption and Scattering
Outline
•  We will use a point-dipole approximation and consider two applications:
–  Enhanced solar cell absorption
–  Enhanced Raman scattering
Plasmonic Near-Field Enhanced Absorption and Scattering
Enhanced solar absorption
•  Metallic nanoparticles and/or
nanostructures can be used:
–  on the surface
–  inside the semiconductor
–  on the back contact
metal nanodisks or nanowires
•  Enhancement due to:
–  scattering
–  LSPR near-fields
back metal contact
metal nanoparticles
metal nanodisks or nanowires
back metal contact
back metal contact
Plasmonic Near-Field Enhanced Absorption and Scattering
Theory of SPR near-field enhancement
E0
k,ω
Au nanoparticle
z
2a
h
y
x
Plasmonic Near-Field Enhanced Absorption and Scattering
Theory of SPR near-field enhancement
E0
k,ω
z
y
x
for a<<λ
Plasmonic Near-Field Enhanced Absorption and Scattering
Theory of SPR near-field enhancement
z
θ
x
φ
y
Plasmonic Near-Field Enhanced Absorption and Scattering
Theory of SPR near-field enhancement
z
for r<<λ the dominant term is the
θ
x
φ
y
absorption enhancement
Plasmonic Near-Field Enhanced Absorption and Scattering
Absorption enhancement
•  at a point
•  on a plane
•  within a volume
Plasmonic Near-Field Enhanced Absorption and Scattering
Planar absorption enhancement
L
– 
Multiple scattering → Claussius-Mossotti
– 
Absorption in the nanoparticle → reduced field strength
Plasmonic Near-Field Enhanced Absorption and Scattering
Planar absorption enhancement
Plasmonic Near-Field Enhanced Absorption and Scattering
Planar and volume absorption enhancement
Plasmonic Near-Field Enhanced Absorption and Scattering
Volume enhancement of composites
Plasmonic Near-Field Enhanced Absorption and Scattering
Surface-Enhanced Raman Scattering
virtual energy
level
vibrational
state
ground state
Schedin et al., ACS Nano 4, 5617 (2010)
Plasmonic Near-Field Enhanced Absorption and Scattering
Theory of SERS in 2d
z
θ
x
φ
y
Plasmonic Near-Field Enhanced Absorption and Scattering
Theory of SERS in 2d
This excites a Raman dipole
z
θ
x
φ
y
Plasmonic Near-Field Enhanced Absorption and Scattering
Theory of SERS in 2d
This excites a Raman dipole
z
which re-radiates exciting a
secondary dipole in the nanoparticle
θ
x
φ
y
Plasmonic Near-Field Enhanced Absorption and Scattering
Theory of SERS in 2d
This excites a Raman dipole
ks,ωs
z
which re-radiates exciting a
secondary dipole in the nanoparticle
θ
x
φ
y
total particle-induced Raman emission
Plasmonic Near-Field Enhanced Absorption and Scattering
Theory of SERS in 2d
assume square array with side L
L
Normalize with the signal I0 expected without nanoparticles
Plasmonic Near-Field Enhanced Absorption and Scattering
Validation of 2d SERS theory
10nm nanoparticles
Ey
Ex
140nm nanoparticles
Plasmonic Near-Field Enhanced Absorption and Scattering
FDTD SERS calculations: model
Au
Cr
SLG
Drude-Lorentz model:
1 free electron & N bound electrons
Plasmonic Near-Field Enhanced Absorption and Scattering
FDTD SERS calculations: method
monitor the field at graphene
Fourier transform
normalize to field without Au disks
absorption enhancement
emission enhancement
Plasmonic Near-Field Enhanced Absorption and Scattering
Raman enhancement
absorption enhancement
Plasmonic Near-Field Enhanced Absorption and Scattering
Conclusions and acknowledgements
•  Simple description of plasmonic
near-field effects based on a
discrete dipole
–  enhanced absorption in
semiconductors
–  SERS in 2d materials
•  insight for designing plasmonic
response
Happy
Birthday
Costa!
Computing time provided
by RCSS Ioannina
Semiconductor absorption
•  University of Patras
–  M.M Sigalas
•  N.C.S.R “Demokritos”
–  N. Lagos
SERS in graphene
•  Cambridge University
–  A.C. Ferrari
–  A. Lombardo
•  University of Manchester
–  K.S. Novoselov
–  A.K. Geim
–  A.N. Grigorenko
–  F. Schedin
–  V.G. Kravets
Plasmonic Near-Field Enhanced Absorption and Scattering
FDTD scheme with dispersion
•  Include polarization terms in Maxwell’s equations
reflection
transmission
absorption
effective medium
band structure
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