Predicting ¿c-Si:H crystal orientation from Raman measurement under polarized light

The determination of the dominant crystal orientation is of great importance in gaining insight into the growth mechanisms of hydrogenated microcrystalline silicon (¿c-Si:H). However, for this purpose most techniques are time-consuming, expensive and destructive. In this contribution, a new approach is investigated to determine crystal orientation in ¿c-Si:H films from Raman spectrum. Raman measurements have been applied under varying polarization angles to a series of samples of varying crystalline volume fraction (fc) covering the transition from amorphous to microcrystalline silicon regime. First, the dependence of the Raman intensity of the 520 cm¿1 TO peak on polarization angle is measured on [100], [110], and [111] single-crystalline silicon wafers. We found distinct patterns for these reference wafers and have used these patterns as a fingerprint for a specific crystal orientation in ¿c-Si:H. Subsequently, we measured the Raman intensity of the TO peak as a function of polarisation angle on the ¿c-Si:H films and compared the obtained patterns with that of the references. For most of the rf PECVD ¿c-Si:H samples we obtained a dominant crystal orientation of [111]. We found that the dominant crystal orientation is independent of the crystalline volume fraction of the ¿c-Si:H. The inferred crystal orientation will be compared with XRD results.