Spectroscopic studies of low-temperature synthesized nanocrystalline silicon oxy-carbide thin films

Abstract

Low-temperature synthesis of intrinsic nanocrystalline silicon oxy-carbide thin films has been performed by conventional RF-PECVD operated at moderate power P ∼ 260 W.Film prepared at substrate temperature ∼ 170 °C has electrical conductivity ∼ 10–3 S cm−1, optical band gap ∼ 1.96 eV with moderate crystallinity XC. After adequate doping, the material could be useful in the fabrication of the window layer of the all-silicon tandem solar cells.The thin film with substantial crystallinity and a moderate ultra-nanocrystalline (unc-Si) component comprises two distinct and significantly different phases, the nc-Si and the a-SiOxCy:H matrix component, which exhibit different relaxation patterns, at high frequency for the nc-Si and at low frequency for the a-SiOxCy:H counterpart. However, the film prepared at a lower TS, possessing a lesser crystallinity and a higher fraction of unc-Si, exhibits just one combined relaxation peak at a mid-frequency, implying that the insignificant amount of the purely nc-Si phase cannot demonstrate its characteristic relaxation kinetics because of the absence of its own prominent identity in the overall matrix, which is dominated mainly by the a-SiOxCy:H component.