Mechanisms of radiation damage in beam-sensitive specimens, for TEM accelerating voltages between 10 and 300 kV.
Ionization damage (radiolysis) and knock-on displacement are compared in terms of scattering cross section and stopping power, for thin organic specimens exposed to the electrons in a TEM. Based on stopping power, which includes secondary processes, radiolysis is found to be predominant for all incident energies (10-300 keV), even in materials containing hydrogen. For conducting inorganic specimens, knock-on displacement is the only damage mechanism but an electron dose exceeding 1000 C cm(-2) is usually required. Ways of experimentally determining the damage mechanism (with a view to minimizing damage) are discussed.
Physics Department, University of Alberta, Edmonton, Canada. regerton@ualberta.ca
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Egerton