A detailed study of hydrogenated amorphous silicon (a-Si:H) surfaces during etching and subsequent low temperature (T≤200°C) oxidation was carried out using in-situ and spectroscopic ellipsometry (SE). The microstructural information from SE is correlated with the properties of the corresponding evaporated Pd Schottky barrier structures. Oxide layers thinner than ∼ 10 Å have little effect on the diode characteristics and electron surface recombination velocities. This is consistent with a porous structure for these oxides. Evidence is found from growth kinetics that higher density, compact oxide growth occurs for greater thicknesses. These oxides have a large effect on electron transport and surface recombination velocities consistent with the formation of metal-insulator-semiconductor structures.