Application of real-time in situ spectroscopic ellipsometry and infrared spectroscopy for characterizing interface structure of a-Si:H layer

We have applied real-time in situ spectroscopic ellipsometry (SE) and infrared attenuated total reflection spectroscopy (ATR) to investigate a-Si:H nucleation process on substrate that affects the resulting a-Si:H/substrate interface structure significantly. The analyses of these real-time measurements show the formation of a 30 Å thick H-rich interface layer having an average hydrogen content of 20 at.% on a c-Si substrate covered with native oxide (30 Å). This interface layer formation is primarily caused by the H-rich three-dimensional island growth on the substrate. We found a weak dependence of interface layer properties on a-Si:H deposition conditions. This result suggests that the interface layer formation is controlled by the nucleation site density of a-Si:H islands on the substrate, rather than plasma conditions.