Mechanism for formation of ultra thin SiNx on a-Si - XPS and FTIR studies

The mechanism of the formation of in-situ ultra thin silicon nitride (SiNx) layer (< 2 nm) on amorphous silicon (a-Si) layer has been studied by Fourier transform infra-red spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The ultra-thin SiNx layers have been obtained through a hot-wire chemical vapor deposition (HWCVD) route. Approximately 1–4 nm thick films of SiNx were obtained on 12 nm and 40 nm thick a-Si at nitriding temperatures of 250 °C and 850 °C. FTIR of the ultra-thin SiNx layer reveals the radicals of decomposed (NH3) gas reacts with a-Si to form SiNx. Further, our XPS results corroborate this mechanism for the formation of SiNx and confirms the formation of ultra thin SiNx layers. This work will enable the development of Si quantum well (Si-QW) superlattice and Si quantum dot (Si-QD) superlattice structures based on a-Si for third generation (3G) solar photovoltaics.