The role of surface in sputtered amorphous silicon: An oxidation study

High porosity amorphous silicon samples were produced by dc-sputtering in high argon pressure. Post-deposition oxidation and correlated effects were studied in order to elucidate the surface contribution to the measured properties. Infrared spectroscopy, used to follow the oxygen concentration during the oxidation process, allows us to detect the way in which the oxygen is attached. The electron spin density, absorption edge, and dark conductivity are measured in correlation with the oxygen content. We conclude that, for this material, dangling bonds are preferentially located near the inner surface of the porous structure. It is suggested that band bending is responsible for conductivity enhancement and two alternative mechanisms are proposed to explain the absorption edge shift.