Microprobe Raman spectroscopy of TiN coatings oxidized by solar beam heat treatment

Physical vapor deposited TiN coatings oxidized by solar beam heat treatment in air were examined by microprobe Raman spectroscopy. The Raman spectra of TiN treated at 400 °C indicated incipient oxidation by the presence of anatase TiO₂ and additionally showed a broadband feature around the forbidden TiN vibrational mode. Inhomogeneous mixtures of rutile TiO₂ and small amounts of anatase polymorph (< 10%) were detected for the treatments at 600 °C only during the initial stage of oxidation. Prolonged treatment at 600 °C resulted in a complete anatase-to-rutile conversion. Rutile was identified as the single product of oxidation of the TiN samples treated at 800 °C. Peak analysis of the rutile spectra revealed no substantial spectral shifts, demonstrating an oxide growth of nearly stoichiometric rutile with an estimated composition in the range of TiO_2±0.02. The Raman scattered light intensity could be correlated with the rutile layer thickness.