Download The Scanning Transmission Electron Holography Microscope

The Scanning Transmission Electron
Holography Microscope
(STEHM)
MSC/SMC
June 5-8, 2012
Halifax, NS
Rodney Herring
University of Victoria,
Victoria, BC Canada
V8W 2Y2 ([email protected])
Scanning Transmission Electron Holography
Microscope (STEHM) Infrastructure
STEHM – Hitachi HF3300V
Fischione Ion Miller
(Model 1010)
SEM – Hitachi S4800
(+ Bruker EDS)
Fischione Plasma Cleaner
(Model 1020)
FIB – Hitachi HB-2100
Hitachi UV Cleaner
(ZoneSEM)
Pelco Carbon Coater
(Cressington 208C)
+ Anatech Metal Coater (Au+Pd)
Scanning Transmission Electron
Holography Microscope (STEHM)
Special features of STEHM
•  Accelerating voltage
•  Electron source
•  Probe forming lenses
•  Focusing lenses
•  Projector lenses
•  Base unit
•  Housing laboratory
•  The STEHM can perform all conventional TEM and STEM
imaging and analytical methods but just a lot better.
•  Everything that’s good for electron holography is good
for high resolution imaging.
The STEHM
Accelerating Voltage (The Top Hat)
•  Can be used at 300 kV, 200 kV and 60 kV
•  Multiple voltages enable multiple variables of the
specimen to be determined by electron holography
•  300 kV for ultra-high spatial resolution, high-beam
current studies
•  200 kV for specimens that damage at 300 kV but not at 200
kV, e.g., silicon.
•  60 kV for beam sensitive, biological specimen
•  Carbon displaces at ~80 kV
•  Still able to obtain 1 Å resolution (0.7 Å measured)
The STEHM
The Electron Source (The Brains)
•  New Cold-FEG Electron Gun Assembly
•  New materials – very stable in high vacuum.
•  Electron emitter – tungsten (W) single crystal (~10 nm dia)
•  Improved vacuum to 10-13 torr (10-11 Pa)
•  Just one order less than deep space
•  Reduced deposition of H on W electron emitting surface
•  Electron emission improved by 3x
•  Previously, Cold-FEG 10x brighter than standard Schottky
FEG
•  Now 30x brighter than standard Schottky FEG
•  permanently stable at high electron emission
The STEHM
The Electron Source (The Brains)
•  Improved electron energy spread
•  ~ 0.3 eV
•  Can be reduced by reducing electron extraction voltage
•  Ultimate performance not yet measured (EELS)
•  Energy spread decreases (improves) with age of emitter
•  Necessary for energy-filtered imaging (GIF) and energyfiltered holography measuring bandgaps and quasiparticle
properties
•  most coherent electron source of any machine
•  Required for high resolution imaging and high resolution
holography
•  Excellent starting point for the electron optics to follow
The STEHM
Probe Forming Lenses (Condenser Lenses)
•  Substantially improved over HF3300 performance
•  Ultra low-noise, quiet electronics
•  Ultra stable lens currents
•  Ultra quiet switches between STEM & TEM modes
•  Smallest probe size not yet determined but will be
much better than 1.0 Å (~ 0.5 Å – 0.7 Å)
The STEHM
Probe Forming Lenses (Condenser Lenses)
Special condenser lens apertures
Dislocated hologram aperture
•  For changing electron beam from plane wave to
electron vortex beams
•  For manipulating specimen’s electrons, atoms
and nanostructures
•  Used to filter electron spin polarized electrons
Electron Biprism
•  One electron biprism above specimen
•  Forms two beams
•  For STEM holography and Confocal Electron
Holography
Formation of Electron Vortex Beams
B J McMorran et al. Science 2011;331:192-195
Electron Vortex Beam from Dislocated Hologram
Creation of spiral-type wave from a plane wave using
hologram with a dislocation.
R A Herring Science 2011;331:155-156
Herring & Pozzi, Intro to EH (1999).
Electron vortex beams carry orbital angular momentum
(OAM) useful for:
•  atomic and subatomic scale manipulations
stir up currents in superconductors
apply magnetic fields at the nanoscale
pick and place molecules and atoms
make and break electronic bonds (tweezers)
•  enable new chemical, crystallographic, optical, electronic, and
magnetic information about a sample
•  enable new technique for magnetic imaging
•  enable spiral phase microscopy in a TEM
•  enhance the visibility of edges in samples with low absorption
contrast, such as unstained biological specimens,
macromolecules, carbon nanotubes, and polymers, without
sacrificing spatial resolution.
•  new capabilities for electron energy loss spectroscopy (EELS) in
a TEM
•  the dark intensity node of the vortex could be used to improve
the spatial resolution of the electron microscope
R A Herring Science 2011;331:155-156
The STEHM
Focusing Lenses (The Heart)
•  First Cs + Cc corrected STEM
•  Ultra small, high-current electron probe better
than 0.7 Å expected
•  Using Secondary Electron detector can see
surface atoms and atomic structures of
specimen
•  For use with HAADF detector for Z-contrast
imaging and performing AEM (analytical
electron microscopy)
•  Necessary for interrogating electron densities
between atomic columns of crystals
•  For characterization of point defects and small
electronic defects, eg., EL2 defect in GaAs.
The STEHM
Focusing Lenses (The Heart)
•  STEM Cs + Cc corrector
•  Contains EXB Wien filter
•  Only electron microscope with Wien filter
•  May be possible to produce spin polarized
electron beams having electron spin
momentum
•  Opens up new research involving:
• 
electron and nuclear spintronics
• 
measurement and characterization of
magnetic potentials at atomic scale.
Scanning Transmission Electron
Holography Microscope (STEHM)
Focusing Lenses (The Heart)
Object lens pole piece
•  same as NRC NINT’s HF3300
•  +15o rotation using standard holder
•  tomography holder available with 360o rotation
•  Ultra-clean vacuum using ZoneTEM
•  Cs – who cares?
STEHM
Focusing Lenses (The Heart)
•  First Aplanatic TEM
•  First Cs and coma corrected TEM
•  Cc partially corrected
•  Coma correction increases high resolution
field-of-view imaging area by 10x
•  Area increased from ~100 nm to ~one micron
diameter
•  Ultimate spatial resolution not yet determined
•  Better than 50 pm measured
•  Spatial resolution improved using UVic’s $1.2M
STEHM Lab
The STEHM
The Intermediate Lenses (The Legs)
•  One extra projection lens – higher magnification
•  Accommodate 3 electron biprisms below specimen
•  For new types of beam interference/holography
•  eg., 3D confocal electron holography, directly
imaging the specimen’s phase information, etc
•  Magnification between biprisms made equal to one
•  Enables lensless, double energy-filtered lattice
imaging, etc
•  Can split electron wave into four pieces by also using
condenser electron biprism above specimen
•  Great for quantum mechanic studies involving
frustrated electrons and quantum communications
The STEHM
The Intermediate Lenses (The Legs)
•  Electron holography
•  Hologram carrier fringes down to ~4 pm
•  Fringes can be able to measure electron wave
disturbances due to vibrations less than the
wavelength of the electron, i.e., < 2 pm
•  May be possible to use for monitoring Earth’s
plate tectonics
•  ~ 1 million times better than using LASER
The STEHM
The Base (The Feet)
• 
• 
• 
• 
• 
• 
New Base developed for STEHM
Steel composite
More rigid
More vibration dampening
Ultra-stable mechanically
Necessary for high column (~4.5 m) of STEHM
The STEHM Lab
STEHM Lab (The Home)
•  Five layers of walls protect the STEHM
•  Aluminum outer wall to remove stray electromagnetic
fields
•  Steel-clad thermal insulation wall to help maintain room
temperature to + 0.1 oC per hour.
•  Mu metal shielding to remove stray magnetic fields
including protection around PEELS/GIF
•  Cooling panels + quiet HVAC with wrap-around sock for
diffuse room air
•  Isolated foundation directly on top of bed-rock
•  Sound reducing panels
•  Over-pressurized room to remove barometric pressure
fluctuations
The STEHM
Special accessories of STEHM
•  Has almost all analytical and imaging accessories
•  SE - Secondary Electron detector for seeing surfaces
•  EELS – electron energy loss spectrometer for
determining composition (light elements) and
molecular state of atoms and molecules
•  EDS – x-ray energy dispersive spectrometer for
compositions (atomic column x atomic column
should be possible)
The STEHM
Special accessories of STEHM (cont’d)
•  Imaging energy filter (GIF – Gatan Imaging Filter) for
energy-filtered imaging and higher magnification
imaging (20x)
•  HAADF – high-angle annular dark field imaging (highresolution Z-contrast imaging)
•  HAABFD - high-angle annular bright field imaging (highresolution STEM imaging)
•  Still needed - Cathodoluminescence detector for
optoelectronic materials
The STEHM
Specimen holders of STEHM
•  High-stability single tilt holder for high-resolution
imaging
•  Double-tilt low background for analytical electron
microscopy
•  Tomography (360o rotation) for 3-dimensional
imaging
•  High-stability high-temperature holder (1500 oC) for
molecular dynamic studies
•  Liquid N2 holder for beam sensitive specimens and
low-temperature studies
•  Flash freezer for biological fluid specimens (cryoEM)
The STEHM Lab
The Cost
•  See Excel spread sheet
STEHM Akira Tonomura Fellowship
•  In honour of Dr. Akira Tonomura who passed away on
May 2, 2012
•  Winner of: Emperor Award, Benjamin Franklin
Award, Royal Society Award, Honda Award, etc
•  To support one scientist and one engineer to use
STEHM at UVic for periods of time varying from one
month to one year.
•  Several fellowships each year are expected to be
granted.
•  Theoretical to experimental studies involving STEHM
•  Open to anyone from academia, government, industry
and independents.
Some STEHM Studies
•  electron & nuclear spin momentum studies
•  electron vortex beam specimen manipulation
•  coherence measurement of quasiparticles
•  molecular dynamics using TDS electrons
•  measurement of time using TDS electrons
•  Stobbs factor – quantitative HREM
•  3D strain field measurements using HOLZ and
confocal electron holography
•  protein crystal structures - nucleation and growth
•  short range structure of amorphous materials
•  next generation gene sequencing
•  monitoring Earth s tectonic motions
•  etc., etc., etc.
Summary
The STEHM
•  One awesome electron microscope
•  Enabling awesome science
In Conclusion
Don’t use the ABNORMAL infrastructure
Use the STEHM infrastructure for what its worth!
See:
Lab Manager - Elaine Humphrey
STEHM infrastructure Trainer – Adam Schuetze
http://stehm.uvic.ca/
Acknowledgements
•  Canadian Foundation for Innovation
•  British Columbia Knowledge Development Fund
•  Hitachi High Technologies Canada
•  University of Victoria