Photoemission and photoyield of amorphous Si films

We have studied the electronic structure of in situ sputtered amorphous Si (a-Si) and hydrogenated amorphous Si (a-Si:H) films with the use of angle-integrated photoemission with synchrotron radiation. The valence-band emission gives evidence for the presence of Si--H--H--Si broken-bond configurations in the film. Combining Si 2p core-level photoemission measurements with photoabsorption (photoyield) studies of the Si 2p edge, we have also followed the evolution of the band gap with sample preparation and annealing. The band gap decreases with higher annealing temperatures, and the hydrogenated films initially have a 0.3-eV-larger band gap than does a-Si