Diffuse scattering in weak-beam images

Abstract
The importance of the diffuse background in weak-beam electron micrographs is discussed. In typical cases its magnitude, as measured by a displaced aperture technique, is about 0-005 relative to the incident beam intensity and roughly equal to the ’coherent’ (Bragg) background. The role of various diffuse scattering mechanisms is estimated and it is concluded that the magnitude of the diffuse background cannot be adequately explained by thermal diffuse scattering or by disorder scattering from, for example, surface contaminant films. A major contribution arises from scattering due to electronic excitation. The quality of weak-beam images could perhaps therefore be improved by energy filtering.

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