Microstructure and surface roughness of microcrystalline silicon prepared by very high frequency-glow discharge using hydrogen dilution

The microstructure of a series of silicon films deposited by very high frequency glow discharge (VHF-GD) with silane concentration in hydrogen varying from 100% down to 1.25% has been observed with transmission electron microscopy (TEM). The surface topography of the layers has been analysed by atomic force microscopy (AFM). At silane concentration below 8.6%, a phase transition between amorphous hydrogenated silicon (a-Si:H) and microcrystalline silicon (μc-Si:H) is observed by TEM. After this transition, the further decrease of silane concentration leads to complex changes of the crystalline microstructure of the layers. AFM observations of the surface reveal that the film rms roughness increases with the decrease of the silane concentration. The surface morphology is not related simply to the microstructure of crystalline grains as observed by TEM.