Rapid synthesis of nc-Si/a-SiNx:H QD thin films by plasma processing for their cost effective applications in photonic and photovoltaic devices

摘要

A rapid and single step synthesis of nc-Si/a-SiNx:H QD thin films, where nc-Si QDs of size similar to 9-2.6 nm and number density similar to 10(11)-10(12) cm(-2) are embedded in a-SiNx:H matrix, has been made possible from a (SiH4 + NH3) gas mixture, with the advent of high density low pressure planar inductively coupled plasma processing. The nc-Si/a-SiNx:H QD films of high crystallinity (similar to 80%) with preferred orientation /(< 220 >)//(< 111 >) similar to 1, along with the distinct presence of alpha-Si3N4 and beta-Si3N4 components have been obtained at a competitive deposition rate of similar to 20.6 nm min(-1) from an extremely low flow rate (similar to 2.0 sccm) of the feed gas SiH4. The significance of the result lies in attaining such a material from pure SiH4 plasma without H-2-dilution, and that even at a low substrate temperature (similar to 250 degrees C) compatible for device fabrication. Tunable and intense visible photoluminescence (PL), with a variety of individual colors in the range 1.55-3.10 eV, has been demonstrated as a consequence of band-to-band recombination due to quantum confinement effects (QCE). The high magnitude of the confinement parameter (similar to 13.5 eV nm(2)) has been correlated to the core-shell-like structure of the QDs within a dielectric matrix; the amorphous shell-like component surrounding the rigid network of the nc-Si QD core has been revealed by the HR-TEM micrograph. With all their various properties e.g., high crystallinity, favored orientation, wide optical gap due to the quantum confinement in the Si-ncs and a significant amount of nitrogen bonding in the matrix, as well as their photoluminescence, which is tunable over a wide range, the nc-Si/a-SiNx:H quantum dot (QD) thin films obtained at high growth rate have enormous promise for their cost effective applications in silicon based photonic and photovoltaic devices.