Photoluminescence properties of thin-film SiOxCy deposited by O-Cat CVD technique using MMS and TEOS

This work aims to evaluate the properties of deposited SiO_xC_y thin films by means of organic catalytic chemical vapor deposition (O-Cat CVD) technique. The employed precursors were Monomethyl Silane (MMS; (CH₃-SiH₃)) and Tetra-ethyl orthosilicate [TEOS; (Si(OC₂H₅)₄)], which corresponded to gaseous and liquid sources, respectively. The deposition chamber worked under a reactant atmosphere of hydrogen (H₂) and oxygen (O₂), likewise the use of tantalum (T_a) as a catalyst for MMS precursor. TEOS was used at the Argon atmosphere and tungsten (W) as a catalyst. The deposition time was varied from 20 to 30 min in order to evaluate its influence on the luminescent properties of the deposited films. Chemical and bonding-state characterization were performed through Fourier transform infrared (FTIR) and X-ray Photoelectron Spectroscopy (XPS) techniques. The measurements of thickness and refractive index of the thin films were obtained by ellipsometry. Optical properties were evaluated by photoluminescence spectroscopy. The FTIR showed the peak shifting from the stoichiometric stretching value of Si-O-Si bonding (1080 cm^-1) to 1025 cm^-1 and 1036 cm^-1 for MMS and TEOS precursors, respectively. The Si-O-Si bonding shift might come due to the oxygen deficiency in the prepared samples. Through XPS measurements, it was possible to determine different bonding states and their amount through the formation of SiO_xC_y thin films; however, the sample deposited with TEOS shows its nature closer to the SiO_x phase in comparison to MMS deposited thin films. The thickness of thin films increased proportionately with the increment of deposition time. Moreover, the red-shifted PL spectrum was determined for the MMS deposited samples in comparison to TEOS deposited samples. Intense emission in a broad region of the visible spectrum was observed without further thermal annealing process. The different reasons were discussed about the origin of photoluminescence, but still, there is further need for additional studies to determine the PL mechanism.