Correlation of simulated TEM images with irradiation induced damage

Crystal damage induced by irradiation is investigated using transmission el ectron microscopy (TEM) coupled to molecular dynamics (MD) calculations. Th e displacement cascades are simulated for energies ranging from 10 to 50 ke V in Al, Ni and Cu and for times of up to a few tens of picoseconds. Sample s are then used to perform simulations of the TEM images that one could obs erve experimentally. Diffraction contrast is simulated using a method based on the multislice technique. It appears that the cascade induced damage in Al imaged in weak beam exhibits little contrast, which is too low to be ex perimentally visible, while in Ni and Cu a good contrast is observed. The n umber of visible clusters is always lower than the actual one. Conversely, high resolution TEM (HRTEM) imaging allows most of the defects contained in the sample to be observed, although experimental difficulties arise due to the low contrast intensity of the smallest defects. Single point defects g ive rise in HTREM to a contrast that is similar to that of cavities. TEM im aging of the defects is discussed in relation to the actual size of the def ects and to the number of clusters deduced from MD simulations. (C) 2000 El sevier Science B.V. All rights reserved.