Spherical aberration correction has become inevitable in materials science for atomic-resolution imaging of conventional objects by transmission electron microscopy at medium accelerating voltages (80-300kV). However, low-Z and radiation-sensitive low-dimensional objects often require lower accelerating voltages because the threshold for knock-on damage is below 80kV for these materials. Unfortunately, the resolution of spherical aberration-corrected transmission electron microscopy at an accelerating voltage less than 80 kV with a standard Schottky type or field-emission electron source is strongly limited by the chromatic aberration of the objective lens. Here we report on our approach to achieve atomic resolution at voltages in the range between 20-80kV in transmission electron microscopy [1,2,3]. We apply the newly-developed aberration corrector that corrects for both, spherical and chromatic aberration of the objective lens. First experimental results of low-dimensional objects will be presented.
The performance of the SALVE (Sub-Angstrom Low-Voltage Electron microscopy) microscope enables atomic-resolution imaging and high-resolution energy-filtered (EF)-TEM with large energy windows even at 20kV accelerating voltage. Obviously, no damping of the contrast transfer function by chromatic aberration has to be considered in the image calculation routine, although image spread due to thermal magnetic field noise  needs to be taken into account as a new source of contrast transfer damping. The envelope now results from image-spread and residual defocus . Image calculations are performed in dependence of the electron dose . Figure 1 shows experimental HRTEM images of single-layer graphene at 30kV; as the usable aperture is about 65mrad, consequently an information limit of 107pm has been achieved. The comparison of the line profiles through the calculated and experimental images of a defect in graphene demonstrates that a good match has been obtained assuming Si substitutions. Moreover, on the example of TiO2 we demonstrate the new capabilities for EFTEM imaging. We now can use an energy window of about 20 eV where the defocus changes by only about 2 nm. This enables previously reported high-resolution EFTEM  imaging but at low accelerating voltages.
In addition, we discuss the importance of sophisticated sample preparation approaches [8,9] and show results in imaging and spectroscopy on low-dimensional objects [10-15].
 U. Kaiser, J. Biskupek, J.C. Meyer, J. Leschner, L. Lechner, H. Rose, M. Stöger-Pollach, A.N. Khlobystov, P. Hartel, H. Müller, M. Haider, S. Eyhusen and G. Benner Ultramicroscopy 111 (2011), p. 1239.
 M. Linck, P. Hartel, S. Uhlemann, F. Kahl, H. Müller, J. Zach, and M Haider, M. Niestadt and M. Bischoff, J. Biskupek, Z. Lee, T. Lehnert, F. Börrnert, H. Rose, and U. Kaiser (2016) submitted.
 S. Uhlemann Physical Review Letters 111(4) (2013), 046101.
 M. Haider, P. Hartel, H. Müller, Microsc. Microanal. 16(2010), 393.
 Z. Lee, H. Rose, O. Lehtinen, J. Biskupek, U. Kaiser, Ultramicroscopy 145 (2014), 3.
 K. W. Urban, J. Mayer, J. R. Jinschek, M. J. Neish, N. R. Lugg, and L. J. Allen, Phys. Rev. Lett. 110, (2013), 185507.
 G. Algara-Siller, O. Lehtinen, A, Turchanin, U. Kaiser, Appl. Phys. Lett. 104 (2014) 153115.
 G. Algara-Siller, S. Kurasch, M. Segeti, O. Lehtinen, U. Kaiser, Appl. Phys. Lett. 103 (2013) 20310.
 G. Algara-Siller, N. Severin, S. Chong, T. Björkman, R. Palgrave, A. Laybourn, M. Antonietti, Y. Khimyak, A. Krasheninnikov, J. P. Rabe, U. Kaiser, A. Cooper, A. Thomas, M. Bojdys, Angewandte Chemie, 53 (2014) 7450.
 O. Lehtinen, L. Tsai, R. Jalil, R. R. Nair, J. Keinonen, U. Kaiser and I. V. Grigorieva, Nanoscale, 6 (2014) 6569.
 O. Lehtinen, N. Vats, G. Algara-Siller, P. Knyrim, U. Kaiser, Nano Lett. 15 (1) (2015) 235.
 T. Zoberbier, T. W. Chamberlain, J. Biskupek, M. Suyetin, A. G. Majouga, E. Besley, U. Kaiser, A. N. Khlobystov, Small (2016) accepted.
 A. Markevich, S. Kurasch, O. Lehtinen, O. Reimer, N. Hohlbein, X. Feng, K. Müllen, A. Turchanin,
A N. Khlobystov, U. Kaiser, and E. Besley, Nanoscale (2016) accepted.
 A. Botos, J. Biskupek, T. W. Chamberlain, G. A. Rance, C. Stoppiello, J. Sloan, Z. Liu, K. Suenaga, U. Kaiser, A. N. Khlobystov, JACS (2016) accepted.
 The authors greatly acknowledge funding from the German Research Foundation (DFG) and the Ministry of Science, Research and the Arts (MWK) of the federal state Baden-Württemberg, Germany in the frame of the SALVE project.
To cite this abstract:Ute Kaiser; Properties of low-dimensional electron-beam-sensitive objects by spherical and chromatic aberration-corrected low-voltage high-resolution transmission electron microscopy and spectroscopy. The 16th European Microscopy Congress, Lyon, France. https://emc-proceedings.com/abstract/properties-of-low-dimensional-electron-beam-sensitive-objects-by-spherical-and-chromatic-aberration-corrected-low-voltage-high-resolution-transmission-electron-microscopy-and-spectroscopy/. Accessed: April 3, 2020
EMC Abstracts - https://emc-proceedings.com/abstract/properties-of-low-dimensional-electron-beam-sensitive-objects-by-spherical-and-chromatic-aberration-corrected-low-voltage-high-resolution-transmission-electron-microscopy-and-spectroscopy/