Electron beam creation of metastable defects in hydrogenated amorphous silicon: hydrogen collision model

Metastable dangling bond (DB) creation during keV electron-beam irradiation of hydrogenated amorphous silicon (a-Si:H) is explained with the H collisi on model of light-induced metastability and several physically reasonable a ssumptions. Each incident electron creates an electron-hole pair every nm a s it traverses the sample, resulting in a 1-nm-radius 'hot tube' extending from the front to the back surface of a film <40 nm thick. Electron-hole pa ir recombination within the tube excites mobile II out of Si-H bonds. Durin g the 10 ps before the tube cools, mobile H normally annihilates with a DB left at its site of excitation, but it can diffuse up to 2 nm within the tu be. Because mobile H are created so close together, there are occasional H collisions to form a metastable two-H complex. As in light-induced metastab ility, these collisions leave metastable DBs at the sites of excitation. Th e model predicts linear creation kinetics followed by saturation of the def ect density, as observed. (C) 2000 Elsevier Science B.V. All rights reserve d.