An Examination of H Effusion in a-Si:H Using Infrared Spectroscopy

Abstract

We present the results of H diffusion studies on glow discharge (GD) and hot wire (HW) deposited a-Si:H films studied by infrared (IR) spectroscopy. In this technique, a-Si:H films deposited on crystalline silicon are annealed isochronally for fixed times, and after each anneal the decrease in the amount of SiH infrared absorption is carefully measured. We then incorporate these data into the rate equation for loss of SiH bonds due to annealing, enabling the determination of an activation energy to break these bonds and place the H in a site that cannot be measured by IR. The activation energies for device quality GD films are similar to those found in the a-Si:H diffusion literature, suggesting that diffusion parameters can be measured by this method. On the other hand, a similar analysis of data for HW films containing similar H contents is not clear cut. GD and HW samples with lower H content, deposited at higher Ts, are also examined. We discuss these results in the context of film microstructure.