Effect of Plasma Oxygen Content on the Size and Content of Silicon Nanoclusters in Amorphous SiOx Films Obtained with Plasma-Enhanced Chemical Vapor Deposition

Abstract

The influence of Ar + SiH4 + O2 plasma formulation on the phase composition and optical properties of amorphous SiOx films with silicon nanoclusters obtained using PECVD with DC discharge modulation was studied. Using a unique technique of ultrasoft X-ray emission spectroscopy, it was found that at a 0.15 mol.% plasma oxygen content, amorphous silicon a-Si films are formed. At a high oxygen content (≥21.5 mol.%), nanocomposite films based on SiOx silicon suboxide containing silicon nanoclusters ncl-Si are formed. It was found that the suboxide matrix consists of a mixture of SiO1.3 and SiO2 phases, and the average oxidation state x in the SiOx suboxide matrix is ~1.5. An increase in the concentration of O2 in the reactor atmosphere from 21.5 to 23 mol.% leads to a decrease in ncl-Si content from 40 to 15% and an increase in the average oxidation state x of SiOx from 1.5 to 1.9. In this case, the suboxide matrix consists of two phases of silicon dioxide SiO2 and non-stoichiometric silicon oxide SiO1.7. Thus, according to the experimental data obtained using USXES, the phase composition of these films in pure form differs in their representation in both random coupling and random mixture models. A decrease in the ncl-Si content of SiOx films is accompanied by a decrease in their sizes from ~3 to ~2 nm and a shift in the photoluminescence band from 1.9 eV to 2.3 eV, respectively.

Keywords

• SiO_x
• plasma-enhanced chemical vapor deposition
• DC discharge modulation
• silicon nanoclusters
• photoluminescence