MICROPROBE RAMAN-SPECTROSCOPY OF TIN COATINGS OXIDIZED BY SOLAR BEAM HEAT-TREATMENT

Physical vapor deposited TiN coatings oxidized by solar beam heat trea tment in air were examined by microprobe Raman spectroscopy. The Raman spectra of TiN treated at 400-degrees-C indicated incipient oxidation by the presence of anatase TiO2 and additionally showed a broadband f eature around the forbidden TiN vibrational mode. Inhomogeneous mixtur es of rutile TiO2 and small amounts of anatase polymorph (<10%) were d etected for the treatments at 600-degrees-C only during the initial st age of oxidation. Prolonged treatment at 600-degrees-C resulted in a c omplete anatase-to-rutile conversion. Rutile was identified as the sin gle product of oxidation of the TiN samples treated at 800-degrees-C. Peak analysis of the rutile spectra revealed no substantial spectral s hifts, demonstrating an oxide growth of nearly stoichiometric rutile w ith an estimated composition in the range of TiO2+/-0.02. The Raman sc attered light intensity could be correlated with the rutile layer thic kness.