COMPOSITIONAL AND OPTICAL CHARACTERIZATION OF RF SPUTTER DEPOSITED TEOX THIN-FILMS FOR OPTICAL DISK APPLICATION

Tellurium suboxide (TeOx) thin films have been realized by rf reactive sputtering deposition by using a Te target and an Ar-O2 gas mixture. Non-stoichiometric films with different compositions, with x values ranging from 0.5 to 2, have been obtained by changing deposition parameters such as the oxygen concentration in the gas mixture, the total gas flow and the gas pressure during the deposition. The Te and O atomic concentrations and the mean value of x in the samples have been measured by RBS. XPS analysis has shown that Te atoms are both in metal and oxidized forms and that the metallic Te atomic per cent decreases as the x value increases. From transmittivity and reflectivity measurements the refractive index n and the extinction coefficient k (at the wavelength of 830 nm) have been evaluated and their behaviour as a function of sputtering conditions and post-deposition annealing process has been analysed, with the aim to use these films as optical disk recording media. Films with 0.7 < x < 1.2 show the highest relative variation in n and k after heat treatment at 200-degrees-C for about 5 min.