The Rise of Low Voltage Electron Microscopy for Quantum Materials ResearchThursday (29.09.2016) 09:45 - 10:15 Part of:
Combinations of different quantum materials are of high interest to explore new phenomena and act as the foundation for future electronic devices at the nanometer scale. Our quantum materials research is widely spread, reaching from defect formation in graphene to the characterization of hybrid quantum materials. Our work utilizing Low-Voltage High-Resolution Electron Microscopy (LV HREM) has shown results not possible with intermediate voltage systems. One advantage is our ability to use our electron monochromator to reduce the effects of chromatic aberration as well as improving the Electron Energy Loss signal for optical components. Low voltage imaging has several significant advantages, including increased cross-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 unexpectedly strong surface-plasmonic absorption at the interface of silver and high-index dielectrics based on electron and photon spectroscopy. The measured bandwidth and intensity of absorption deviate significantly from the classical theory. Our density-functional calculation well predicts the occurrence of this phenomenon. It reveals that due to the low metal-to-dielectric work function at such interfaces, conduction electrons can display a drastic quantum spillover, causing the interfacial electron-hole pair production to dominate the decay of surface plasmons . This finding can be of fundamental importance in understanding and designing quantum nanoplasmonic devices that utilize noble metals and high-index dielectrics.
We have also examined a Kagome ferromagnet, the Low Voltage (S)TEM images mapped with low voltage EELS show the atomic structure of the layered material, and the magnetic force microscopy measurements reveal the magnetic anisotropy of the crystal on the surface. Low-Voltage TEM offers significant improvement in contrast for inorganic materials, biological samples and especially nano-biological samples while retaining atomic resolution. Application of Low-Voltage Electron Microscopy and its development and future directions will be presented.