U. Kaiser, J. Biskupek, J. Meyer, J. Leschner, L. Lechner, H. Rose, M. Stöger-Pollach, A. Khlobystov, P. Hartel, H. Müller, M. Haider, S. Eyhusen, G. Benner:
"Transmission electron microscopy at 20 kV for imaging and spectroscopy";
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 20keV. The highly stable instrument is equipped with an electrostatic monochromator and a C(S)-corrector. At 20kV it shows high image contrast even for single-layer graphene with a lattice transfer of 213pm (tilted illumination). For 4nm thick Si, the 200 reflections (271.5pm) were directly transferred (axial illumination). We show at 20kV that radiation-sensitive fullerenes (C(60)) within a carbon nanotube container withstand an about two orders of magnitude higher electron dose than at 80kV. 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 20kV 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.
Low-voltage TEM Beam damage High resolution EELS
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