Investigation of Crystallinity Depth Profile in Thin Film µc-Si:H on Different Substrates

In this work we report a simple approach by which we are able to probe crystallinity evolution in thin film microcrystalline silicon (¿c-Si:H) using depth-profile Raman measurement. Crystalline volume fraction f, is used as a measure of crystallinity indicator and varies with varying film growth phases. Each phase is identified by certain range of crystalline volume fraction extracted from the phase material. Our investigation shows that radio frequency plasma enhanced chemical vapour deposition (rf PECVD) growth of ¿c-Si:H evolves through various material phases from an initial amorphous incubation layer (ASIC) through other phases into the full microcrystalline regime. We found that f increases gradually in growth direction and saturates at the full microcrystalline regime. By means of seeding, we show that we are able to modify the growth process such that ¿c-Si:H evolution is more rapid, more uniform, less dependent on substrate and begins nearly directly from the crystalline phase hence omitting the amorphous and proto-crystalline phases. X-ray diffraction measurement is used to further investigate the structure of ¿c-Si:H grown on different substrates with and without seed layers and the results are also presented.