Optical Properties and Microstructure of TiNxOy and TiN Thin Films before and after Annealing at Different Conditions

TiN and TiNxOy thin films share many properties such as electrical and optical properties. In this work, a comparison is conducted between TiN (with and without annealing at 400 °C in air and vacuum) and TiNxOy thin films deposited by using RF magnetron sputtering with the same pure titanium target, Argon (Ar) flow rate, nitrogen flow rates, and deposition time on stainless steel substrates. In the case of TiNxOy thin film, oxygen was pumped in addition. The optical properties of the thin films were characterized by spectrophotometer, and Fourier transform infrared spectroscopy (FTIR). The morphology, topography, and structure were studied by scanning electron microscope (SEM), atomic force microscope (AFM), and X-ray diffraction (XRD). The results show that both thin films have metal-like behavior with some similarities in phases, structure, and microstructure and differences in optical absorbance. It is shown that the absorbance of TiN (after vacuum-annealing) and TiNxOy have close absorbance percentages at the visible range of light with an unstable profile, while after air-annealing the optical absorbance of TiN exceeds that of TiNxOy. This work introduces annealed TiN thin films as a candidate solar selective absorber at high-temperature applications alternatively to TiNxOy.