Scanning Microscopy


Low energy electrons are involved in a large number of analytical techniques for material analysis either as secondary particles or as the primary excitation source. The interaction of these electrons near the surface of solids can be investigated with high-resolution low-energy electron-beam techniques. The results of experiments performed on atomic and molecular solids in the range 0-30 eV with such techniques are reviewed in the present article. The major types of experiments are briefly described and examples of the results obtained from them are given to illustrate the basic mechanisms which control the electron-solid interactions and to provide a description of the basic degradation processes involved during sample irradiation. It is shown that elastic and quasi-elastic scattering of slow electrons can be described in terms of band structure parameters whereas inelastic scattering is usually governed by the formation of transient anions. These anions can decay by stabilization, by producing vibrationally and electronically excited molecules, or by dissociating into a stable anion and a neutral radical. These latter species usually initiate other reactions with nearby molecules causing further chemical damage. It is shown that the damage caused by transient anions can be controlled by modifying its molecular environment.

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