Ultralow Energy Scanning Transmission Electron Microscopy and Graphene

0481337 - ÚPT 2018 CN eng A - Abstrakt
Frank, Luděk - Mikmeková, Eliška
Ultralow Energy Scanning Transmission Electron Microscopy and Graphene.
BIT's 5th Annual Conference of AnalytiX-2017. Conference Abstract Book. Dalian: BIT Goup Global, 2017. s. 223.
[BIT's Annual Conference of AnalytiX-2017 /5./. 22.03.2017-24.03.2017, Fukuoka]
Institucionální podpora: RVO:68081731
Klíčová slova: STEM * graphene * ulatralow energy
Obor OECD: Nano-materials (production and properties)

Over the last decade, even commercially available scanning electron microscopes have employed biasing of the specimen to a high negative potential in order to reduce the landing energy of the illuminating electron beam without deteriorating the image resolution. In this way, the electron energy can be lowered to tens or even units of eV provided facilities are available to align the electrostatic field properly above the specimen. Having the specimen sufficiently thin and therefore penetrable for ultralow energy electrons, we can also implement STEM at these energies by inserting the detector at ground potential below the biased sample. Pilot experiments have verified the performance of ultralow energy STEM on very thin tissue sections not treated with any agents containing heavy metals and on 2D crystals, including graphene. Greatly enhanced intensity of interaction of ultraslow electrons with solids produces very high image signals, even for light elements constituting living matter or for differences in thickness amounting to one atomic layer of carbon. This has enabled us to measure transmissivity for electrons from 0 to 40 eV in dependence of the number of graphene layers. Moreover, we have examined phenomena occurring on surfaces bombarded with very slow electrons under various vacuum conditions in order to compare them with traditional carbonaceous contamination of electron-illuminated surfaces in a standard vacuum. We found slow electrons releasing hydrocarbon molecules instead of decomposing them, resulting in much cleaner surfaces securing the increasing transmissivity of graphene. We have established a range of electron energies not generating local defects in the graphene lattice by means of Raman spectroscopy.
Trvalý link: http://hdl.handle.net/11104/0276914