Studies on rf sputter deposited nickel-tungsten oxide thin films

Thin films of mixed nickel-tungsten oxide, were prepared by rf magnetron sputtering using mixed oxide target and were characterized by X-ray diffraction, UV-Vis-NIR spectrophotometer and micro Raman spectroscopy. All the deposited film was found to be in amorphous nature. The decrease in optical transmittance and transmission threshold shift towards higher wavelength region was observed for the films deposited at higher rf power (200 W). The Raman spectra of as-deposited Ni-W oxide films show two peaks corresponding to one-phonon LO mode at 560 cm^-1 and two-phonon LO mode at 1100 cm^-1 due to the vibrations of Ni-O bonds and a strong peak at 870 cm^-1 which corresponds to stretching vibration of the W-O pair in the WO₆ group, a so-called 'internal' mode. With increasing rf power the overall Raman intensity increases with increase in nickel-tungsten oxide content. (author)