Microcrystalline silicon nucleation sites in the sub-surface of hydrogenated amorphous silicon

We have characterized surface structures of hydrogenated amorphous silicon (a-Si:H) by applying infrared attenuated total reflection spectroscopy, in order to investigate the phase transition from a-Si:H to microcrystalline silicon (μc-Si:H). At the onset of μc-Si:H nucleation from the a-Si:H phase, an infrared absorption peak at 1937±5 cm−1 assigned to the SiHn (n=1–2) complex is detected in a 5-Å thick region of the a-Si:H sub-surface. The SiHn complex concentration within the a-Si:H sub-surface region showed a clear relationship with the μc-Si:H nucleation. We propose that the SiHn complex, formed by insertion of H into a strained Si–Si bond, contributes to the reactions that result in μc-Si:H nucleus formation.