SiOx thin films were prepared using magnetron sputtering with different O2 flow rates on a silicon substrate. The samples were characterized using Fourier transform infrared spectroscopy in transmission and reflection, covering a spectral range of 5 to 25 μm. By employing a multilayer model, the values of the complex refractive index that best fit the experimental transmission and reflection results were optimized using the Brendel-Bormann oscillator model. The results demonstrate the significance of selecting an appropriate range of O2 flow rates to modify the SiOx stoichiometry, as well as how the refractive index values can be altered between those of Si and SiO2 in the mid-infrared range.
Keywords: mid-infrared; optical properties; refractive index; silicon oxide; thin film.