Scanning Reflection Electron Microscopy of Surface Topography by Diffusely Scattered Electrons in the Scanning Electron Microscope

K. Z. Baba-Kishi

The Hong Kong Polytechnic University, Department of Applied Physics, Hung Hom, Kowloon, Hong Kong

Full-text (for Scanning subscribers)

Summary: In this paper, the technique of scanning reflection electron microscopy (SREM) by diffusely scattered electrons in the scanning electron microscope is described in detail. A qualitative account of the formation of image contrast in SREM is also described. It is assumed that, for grazing geometry, forward-scattered electrons reflect from regions close to the surface, following a few scattering events within the first few atomic layers, and lose very little energy in the process. The penetration depth of the primary electrons is very limited, resulting in strongly peaked envelopes of forward-scattered electrons. It is also assumed that a surface containing topographic features presents a range of tilt angles, resulting in different reflection coefficients. Tilt contrast results because each facet has a different scattering yield, which is dependent upon local surface inclination. Full details of the instrumentation designed for SREM are described, and to illustrate the technique, results recorded from an epitaxial GaAs on GaAs crystal, Pb₂(Zr,Ta)O₆ thin film on silicon, and SiO₂ amorphous film on silicon are presented.

Key words: diffuse scattering, low-loss electrons, angular distribution of backscattered electrons, reflection electron microscopy, scanning electron microscope, surface topography