A real time study of the growth of microcrystalline silicon on transparent conducting oxide substrates

A detailed real time ellipsometry study of the growth of microcrystalline silicon (μc-Si) films on transparent conducting oxide (TCO) substrates is presented. Indium tin oxide and ZnO substrates are compared. μc-Si films prepared either from a high power (SiH4,H2) plasma or by alternating the SiH4 and H2 plasmas (layer-by-layer technique) are considered. Insights into the mechanisms of the TCO/μc-Si interface formation are obtained. A strong chemical reduction of the TCO substrate is observed during the early stage of exposure to the (SiH4,H2) plasma. Then the ellipsometric measurements reveal an induction period of about 1 min before the nucleation of microcrystallites. μc-Si films deposited by the layer-by-layer technique display a different behavior, in particular the chemical interaction at the ZnO/μ-Si interface is not observed in this case.