Optical properties and microstructure of TiN thin films before and after annealing

Titanium nitrides, oxides and oxynitrides (TiN, TiO₂, and TiN _x O _y ) are potential materials for several electronic and optical applications. In this work, TiN thin films are deposited by using RF magnetron sputtering (reactive sputtering type) with a pure titanium target, argon (Ar), and nitrogen (N₂) gases. All sputtered TiN thin films were subsequently annealed in air at 800 C for 2 hours. The microstructure and the optical properties (absorbance and emittance) of sputtered TiN thin films are studied before and after annealing. The optical properties of all thin films before and after annealing are characterized by spectrophotometer, and Fourier transform infrared spectroscopy (FTIR). The morphology and structure are studied by scanning electron microscope (SEM), atomic force microscope (AFM), X-ray diffraction (XRD), and Raman spectroscopy. It was found that the optical absorbance of sputtered TiN thin films is changed after annealing and increased to 94% with a stable profile in ultraviolet (UV), visible range and near infrared (IR) ranges. The initial polycrystalline TiN microstructure is transformed after annealing in air at 800 °C for 2 hours to rutile TiO₂ nanofibers. These nanofibers caused light scattering inside the thin film, which improved the optical absorbance.