Argon sputtering analysis of the growing surface of hydrogenated amorphous silicon films

The surface of freshly deposited hydrogenated amorphous silicon (a-Si:H)films are studied by argon sputtering and mass-spectrometer detection of the sputtered neutral molecules. The surface density of H atoms in the top H-rich layers of the film is established from the initial surge of sputtered H-containing molecules. This shows that the growing film has a hydrogen-rich surface layer of multiply H bonded Si atoms about five monolayers thick on a room-temperature substrate. At the ∼240 °C substrate temperature typical of film production, the thickness of this hydrogen-rich layer decreases to about one monolayer.