Electronic aging and related electron interactions in thin-film dielectrics

The author points out that hot electrons generated in dielectrics subjected to high electrical field strengths can produce highly reactive chemical species which contribute to the aging process. The study of the interaction of such low energy (0 to 15 eV) electrons near the surface of dielectrics in experiments combining cryogenic thin film deposition and high-resolution low-energy electron-beam techniques is discussed. Examples of the results obtained with thin film atomic and molecular solids are used to illustrate the basic mechanisms which control the electron-dielectric interactions and provide a description of the basic degradation processes involved during electronic aging. It is shown that elastic and quasi-elastic scattering of hot electrons in dielectrics can be described in terms of band structure parameters, whereas inelastic scattering is often 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. >