Effect of thermal annealing on the luminescent and structural properties of the SiOxCy thin films by organic catalytic chemical vapor deposition

Photoluminescent silicon oxycarbide (SiO_xC_y) thin films were deposited on n-type (100) silicon substrates using the organic catalytic chemical vapor deposition (OCat-CVD) technique employing tetra-ethyl orthosilicate (TEOS) as an organic-based precursor. These films were annealed at a temperature of 500, 800 and 1000 °C for 30 min in a nitrogen (N₂) environment. The as-deposited and annealed SiO_xC_y films were analyzed using optical and structural characterizations, such as photoluminescence (PL), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), Secondary ion mass spectrometry (SIMS) and scanning electron microscopy (SEM). The PL spectrum of the as-deposited film showed emission in the blue-green region, while the annealed SiO_xC_y films showed strong emission from blue to near-infrared. The PL in all the films was attributed to different structural defects related to oxygen and carbon that act as radiative centers in the SiO_xC_y network. The annealed films showed an increase in the emission intensity, where the annealed film at 800 °C displayed the highest emission intensity. This is related to an increase in the amount of radiative defects in the films due to structural and compositional changes after the thermal annealing (TA). XPS and SIMS measurements showed an oxygen incorporation with the TA, increasing from 54.6 at % to 63.8 at % for the as-deposited and annealed at 1000 °C films, respectively. FTIR spectra showed an increase in the Si-O-C and Si-O-Si bonds and the hydrogen and other radicals desorption. These results support the creation of radiative centers due to structural changes in the films after the thermal annealing.