The splitting of absorption bands in IR spectra of anisotropic SiH monolayers covering the internal surfaces in μc-Si:H

Microcrystalline silicon (μc-Si:H) films with a hardly detectable residual amorphous phase fraction (<5%) have been prepared by hot-wire chemical vapor deposition (HW-CVD). The hydrogen bonding and structure of the internal boundaries in μc-Si:H samples were studied by means of IR spectroscopy. The absorption bands of monohydrides, SiH, and polihydrides, SiH,, were identified with respect to their different thermal stability. A characteristic feature of the IR absorption in μc-Si:H investigated in this paper is the splitting of SiH vibrational modes. The interpretation of this splitting in terms of the absorption of optically anisotropic SiH monolayers covering the internal surfaces in pc-Si:H enables us to identify the absorption lines in IR spectra and to determine the crystallographic orientation of grain boundaries in our μc-Si:H samples.