Electron microscopy of small defect clusters in irradiated metals.nI. The theory of contrast and experimental methods for determination of the type of defect

摘要

Irradiation of metals with particles produces defect clusters which are detectable in the electron microscope. The structure of the defect clusters cannot, however, be deduced from the contrast if the defects are smaller than 150 A. A comparison between specifically designed experiments (dynamical two-beam image) and the results of the contrast theory does, nevertheless, permit determination of the defect type (i.e. the simplest possible shape of the defects and distinction between vacancy and interstitial agglomeration). This analysis is applied to the defects detectable in neutron-irradiated copper. It is shown that almost all the analysed defects may be most simply interpreted as Frank dislocation loops of the vacancy type.