title: Transmission electron microscopy at 20 kV for imaging and spectroscopy.
abstract: The electron optical performance of a transmission electron microscope (TEM) is characterized for direct spatial imaging and spectroscopy using electrons with energies as low as 20 keV. The highly stable instrument is equipped with an electrostatic monochromator and a C(S)-corrector. At 20 kV it shows high image contrast even for single-layer graphene with a lattice transfer of 213 pm (tilted illumination). For 4 nm thick Si, the 200 reflections (271.5 pm) were directly transferred (axial illumination). We show at 20 kV that radiation-sensitive fullerenes (C(60)) within a carbon nanotube container withstand an about two orders of magnitude higher electron dose than at 80 kV. In spectroscopy mode, the monochromated low-energy electron beam enables the acquisition of EELS spectra up to very high energy losses with exceptionally low background noise. Using Si and Ge, we show that 20 kV TEM allows the determination of dielectric properties and narrow band gaps, which were not accessible by TEM so far. These very first results demonstrate that low kV TEM is an exciting new tool for determination of structural and electronic properties of different types of nano-materials.
authors.affiliation: Central Facility of Electron Microscopy, Group of Electron Microscopy of Materials Science, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany. ute.kaiser@uni-ulm.de
authors.forename: U
authors.initials: U
authors.lastname: Kaiser
authors.forename: J
authors.initials: J
authors.lastname: Biskupek
authors.forename: J C
authors.initials: JC
authors.lastname: Meyer
authors.forename: J
authors.initials: J
authors.lastname: Leschner
authors.forename: L
authors.initials: L
authors.lastname: Lechner
authors.forename: H
authors.initials: H
authors.lastname: Rose
authors.forename: M
authors.initials: M
authors.lastname: Stöger-Pollach
authors.forename: A N
authors.initials: AN
authors.lastname: Khlobystov
authors.forename: P
authors.initials: P
authors.lastname: Hartel
authors.forename: H
authors.initials: H
authors.lastname: Müller
authors.forename: M
authors.initials: M
authors.lastname: Haider
authors.forename: S
authors.initials: S
authors.lastname: Eyhusen
authors.forename: G
authors.initials: G
authors.lastname: Benner