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SUMMARY:The Rise of Low Voltage Electron Microscopy for Quantum Materials 
 Research - David C. Bell\, Harvard University 
DTSTART:20161128T100000Z
DTEND:20161128T110000Z
UID:TALK68502@talks.cam.ac.uk
CONTACT:Duncan Johnstone
DESCRIPTION:Combinations of different quantum materials are of high intere
 st to explore new phenomena and act as the foundation for future electroni
 c devices at the nanometer scale. Our quantum materials research is widely
  spread\, reaching from defect formation in graphene to the characterizati
 on of hybrid quantum materials.  Our work utilizing Low-Voltage High-Resol
 ution Electron Microscopy (LV HREM) has shown results not possible with in
 termediate voltage systems. One advantage is our ability to use our electr
 on monochromator to reduce the effects of chromatic aberration as well as 
 improving the Electron Energy Loss signal for optical components.   Low vo
 ltage imaging has several significant advantages\, including increased cro
 ss-sections for inelastic and elastic scattering\, increased contrast per 
 electron and improved spectroscopy efficiency\, decreased de-localization 
 effects and reduced radiation knock-on damage.  We demonstrated an unexpec
 tedly strong surface-plasmonic absorption at the interface of silver and h
 igh-index dielectrics based on electron and photon spectroscopy. The measu
 red bandwidth and intensity of absorption deviate significantly from the c
 lassical theory. Our density-functional calculation well predicts the occu
 rrence of this phenomenon. It reveals that due to the low metal-to-dielect
 ric work function at such interfaces\, conduction electrons can display a 
 drastic quantum spillover\, causing the interfacial electron-hole pair pro
 duction to dominate the decay of surface plasmons . This finding can be of
  fundamental importance in understanding and designing quantum nanoplasmon
 ic devices that utilize noble metals and high-index dielectrics.\n\nWe hav
 e also examined a Kagome ferromagnet\, the Low Voltage (S)TEM images mappe
 d with  low voltage EELS show the atomic structure of the layered material
 \, and the magnetic force microscopy measurements reveal the magnetic anis
 otropy of the crystal on the surface.  Low-Voltage TEM offers significant 
 improvement in contrast for inorganic materials\, biological samples and e
 specially nano-biological samples while retaining atomic resolution. Appli
 cation of Low-Voltage Electron Microscopy and its development and future d
 irections will be presented.
LOCATION:Goldsmiths 1\, Lecture room\, Dept. of Materials Science and Meta
 llurgy
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