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Graphene examined with very slow electrons
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SYSNO ASEP 0450825 Document Type C - Proceedings Paper (int. conf.) R&D Document Type Conference Paper Title Graphene examined with very slow electrons Author(s) Frank, Luděk (UPT-D) RID, SAI, ORCID
Mikmeková, Eliška (UPT-D) RIDNumber of authors 2 Source Title 12th Multinational Congress on Microscopy. - Budapest : Akadémiai Kiadó, 2015 - ISBN 978-963-05-9653-4 Pages s. 182-183 Number of pages 2 s. Publication form Online - E Action MCM 2015. Multinational Congress on Microscopy /12./ Event date 23.08.2015-28.08.2015 VEvent location Eger Country HU - Hungary Event type WRD Language eng - English Country HU - Hungary Keywords graphene ; 2D crystals ; ultra-low-energy STEM ; ultra-low-energy SEM Subject RIV JA - Electronics ; Optoelectronics, Electrical Engineering R&D Projects TE01020118 GA TA ČR - Technology Agency of the Czech Republic (TA ČR) Institutional support UPT-D - RVO:68081731 Annotation Electron microscopy of materials composed of light elements suffers from low image contrast, particularly in the transmission microscopy of biomedical specimens. Post-fixation or staining with heavy metal salts that highlight certain structural details is a partially successful aid in routine microscopy. In order to examine mutually overlapped flakes of two-dimensional crystals such as graphene we need to obtain a contrast contribution from a single layer of carbon atoms. This task requires increasing the scattering rate of incident electrons by means of a drastic lowering of their energy to hundreds of eV or less. The cathode lens principle implemented in the SEM, and recently in the STEM mode as well, makes it possible to use an arbitrarily low energy in both reflection and transmission modes. Contrasts between sites differing in thickness by a single graphene layer are demonstrated at 220 eV. The high lateral resolution of ultra-low-energy STEM with a cathode lens enabled us to measure graphene transmissivity accurately down to 1 eV for 1 to 7 graphene layers. Surprisingly, below 50 eV the transmissivity does not increase as one would expect from the usual behaviour of the inelastic mean free path of electrons, but remains within a range of units of percent. Workplace Institute of Scientific Instruments Contact Martina Šillerová, sillerova@ISIBrno.Cz, Tel.: 541 514 178 Year of Publishing 2016
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