Improved near-infrared luminescence of si-rich SiO2 with buried Si nanocrystals grown by PECVD at optimized N2O fluence

Abstract

The optimized N2O fluence for plasma enhanced chemical vapor deposition (PECVD) growing silicon-rich substoichiometric silicon oxide (SiOx) with buried Si nanocrystals is demonstrated. Strong room-temperature photoluminescence (PL) at 550-870 nm has been observed in SiOx thin films grown by PECVD with N2O fluence varying from 105 to 130 sccm. After annealing from 15 to 180 min, a 22-nm-redshift of the PL has been detected. The maximum PL intensity is observed for the 30-min annealed SiOx growing at N2O fluence at 120 sccm. Larger N2O fluence and longer annealing time causes a PL blueshift by 65 nm and 20 nm, respectively. Such a blueshift is attributed to shrinkage in the size of the Si nanocrystals under the participation of dissolved oxygen atoms from N2O. The (220)-oriented Si nanocrystals with radius ranging from 4.4 to 5.0 nm are determined. The luminescent lifetimes lengthens from 20 mu s to 52 mu s as the nc-Si size extends from 4.0 to 4.2 run. Optimal annealing times for SiOx preparing at different N2O fluences and an optimum N2O fluence of 120 sccm are reported. Serious oxidation effect at larger N2O fluence condition is observed, providing smaller PL intensity at shorter wavelengths. In contrast, the larger size nc-Si will be precipitated when N2O fluence becomes smaller, leading to a weaker PL at longer wavelength. These results provide the optimized growth condition for the Si-rich SiO2 with buried Si nanocrystals.