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 (SiN_x) 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 SiN_x 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 SiN_x 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 SiN_x and confirms the formation of ultra thin SiN_x 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.