Effect of carbon concentration on optical and structural properties in the transition from Silicon Rich Oxide to SiCxOy films formation

The role of carbon atomic concentration on the transition from Silicon Rich Oxide (SRO) to Silicon Oxicarbide films (SiCxOy) is reported. For this, optical and structural properties were analyzed by Photoluminescence (PL), Micro-Raman, Fourier Transform Infrared (FTIR) and X-Ray Photoelectron Spectroscopy (XPS) measurements. An SRO film with 16.6 at.% of Si-excess and SiCxOy films with carbon concentration from 1.3 to 7.2 at.% were grown by Hot Filament Chemical Vapor Deposition Technique (HFCVD). The SRO film (C = 0 at.%) and SiCxOy films with low carbon atomic concentration (C = 1.3 at.%) exhibited a very low PL emission in the red-infrared region (1.5–1.7 eV) manly attributed to SiO defects which are reduced or annihilated by incorporation of carbon. An increase in carbon atomic concentration greater than 1.3 produces a strong PL emission at white region (3.35–1.72 eV) characteristic of SiCxOy films attributed to radiative defects such as defects associated to Si-related oxygen vacancies (Si-NOVs), Si-related oxygen deficiency centers (Si-ODC) and C-related oxygen vacancies (C-NOVs). In this work it was found that a carbon atomic concentration greater that 1.3 is required to have a high density of these radiative defects. Also, due to the high growth temperature (900 °C) and Si-excess (from 16.6 to 3.9 at.%), we propose the presence of Si nanocrystals (Si–NCs) embedded in both SRO and SiCxOy films with low carbon concentration (SiO2-Like characteristics). Whereas an increase in carbon concentration of 7.2 at. %, Si–NCs precipitation was inhibited in the SiCxOy films.