Influence of the substrate on the early stage of the growth of hydrogenated amorphous silicon evidenced by kinetic ellipsometry

Publisher Website
Google Scholar
Abstract
Fast real‐time ellipsometry is used to study in situ, as a function of the substrate, the growth of the first tens of monolayers of hydrogenated amorphous silicon (a‐Si:H) deposited by a rf glow discharge of SiH4. The high sensitivity of this technique is illustrated and the early stage of the growth is found to strongly depend upon the nature of the substrate. A nucleation mechanism followed by incomplete coalescence is observed on metal and hydrogenated amorphous germanium (a‐Ge:H) substrates. On the contrary, fused silica (SiO2) and tin dioxide (SnO2) are superficially reduced: this reduction creates at the interface a mixed layer of a‐Si:H and silicon oxide on the silica substrate, and produces elemental tin at the surface of the SnO2 substrate. In this last case, tin is found to diffuse in the further a‐Si:H growing film. On crystalline silicon (c‐Si), the a‐Si:H growth shows incomplete coalescence followed by homogeneous growth, probably together with the reduction of the native c‐Si oxide layer.