Correlation between photoluminescence and radiative defects in silicon oxycarbide films due to the growth temperature effect

In this work, the effect of growth temperature (678–988 °C) on silicon oxycarbide (SiCxOy) samples obtained by hot filament chemical vapor deposition (HFCVD) is reported. The samples were deposited on silicon (Si) n-type (100) and quartz substrates for optical and structural studies. At a lower temperature (678 °C), silicon oxycarbide powders were formed on Si substrates due to the homogeneous reaction occurring in the gas phase. However, for temperatures between 804 and 988 °C, silicon oxycarbide films were formed on Si substrates. By changing the temperature from 678 to 988 °C, both carbon (C) concentration (21.2–17.7 wt.%) and the relative percentage of Si–C bond density (%RtSi-C = 11.34–3.47 %) decreased, as demonstrated by EDS and FTIR measurements, respectively. On the other hand, the content of relative Si–O–Si bonds located around 1060 cm−1 remained dominant in all cases, resulting in SiCxOy films with an amorphous SiOx-type structure. These films exhibited strong photoluminescence (PL) centered in the blue region (∼3 eV), where Si–NOVS radiative centers were preferentially responsible for PL emission. At a lower temperature (678 °C), the PL intensity decreased. The determination of optical bandgap energy (Eopt) using Tauc Plots coincided with the emission due to luminescent centers (∼3 and ∼2.7 eV) observed in PL, indicating that the radiative transitions were due to defects. The AFM measurements showed an increase in roughness from 5.01 to 16.20 nm as the growth temperature decreased, as expected according to SEM measurements.