On the effects of thermal treatment on the composition, structure, morphology, and optical properties of hydrogenated amorphous silicon-oxycarbide

The composition, structure, morphology, and optical characteristics of hydrogenated amorphous silicon-oxycarbide (a-SiC_xO_yH_z) materials were investigated as a function of experimental processing conditions and post-deposition thermal treatment. Thermal chemical vapor deposition (TCVD) was applied to the growth of three different types of a-SiC_xO_yH_z films, namely, SiC-like (SiC_1.08O_0.07H_0.21), Si-C-O (SiC_0.50O_1.20H_0.22), and SiO₂-like (SiC_0.20O_1.70H_0.24). The resulting films were subsequently annealed at temperatures ranging from 500 °C to 1100 °C for 1 h in an argon atmosphere. The composition, structure, and morphology of as-deposited and post-annealed films were characterized by Fourier transform infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectroscopy (RBS), nuclear-reaction analysis (NRA), and scanning electron microscopy. Corresponding optical properties were assessed by spectroscopic ultraviolet-visible ellipsometry (UV-VIS-SE). These studies led to the identification of an optimized process window for the growth of Er doped silicon oxycarbide (SiC_0.5O_1.0:Er) thin film with strong room-temperature photoluminescence emission measured around 1540 nm within a broad (460 nm to 600 nm) wavelength band. Associated modeling studies showed that the effective cross section for Er excitation in the SiC_0.5O_1.0:Er matrix was approximately four orders of magnitude larger than its analog for direct optical excitation of Er ions.