Thermal diffuse scattering and REM image-contrast preservation

Abstract

The diffuse diffraction spots occurring in reflection high energy electron diffraction (RHEED) patterns and not lying on the circle in which the Ewald sphere intercepts a reciprocal plane have been selected for reflection electron microscopy (REM) imaging of Pt(111) surfaces. Application of the boundary conditions for reflection electron diffraction to the inelastic diffusely scattered electrons requires that the thermal diffuse scattering process gives these diffuse diffraction spots in RHEED patterns, and there is no contribution from elastically scattered electrons to the image contrast. Contrast resulting from surface steps has been observed to be well preserved around the near-focus region in the REM images. It has also been observed that the contrast is smeared out rapidly in the off-focus region due to the diffuseness of the thermal diffuse spot used for REM imaging.