Hydrogen-effusion-induced structural changes and defects in<i>a</i>-Si:H films: Dependence upon the film microstructure

Abstract

In order to better understand the effects of hydrogen incorporation and departure on the defects and the disorder in undoped hydrogenated amorphous silicon (a-Si:H), we performed a comparative study on samples deposited under different plasma conditions. We used a combination of IR absorption spectroscopy, electron-spin resonance, photothermal deflection spectroscopy, constant photocurrent method, and elastic recoil detection analysis measurements to determine the changes in the defect density and in the disorder, as well as in the hydrogen concentration and bonding modes, after isochronal annealing cycles at temperatures up to 500--600 \ifmmode^\circ\else\textdegree\fi{}C. The results, which show a better stability of the bonded hydrogen in the films deposited at high rates, are interpreted as a whole in terms of specific local hydrogen bonding environments, related to different growth mechanisms. \textcopyright{} 1996 The American Physical Society.