Influence of deposition parameters on the optical properties of thin tungsten oxide films prepared by reactive Dc magnetron sputtering
Wangati, C. K.
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Tungsten oxide thin films are the most investigated because of their possible application in electrochromic devices. Studies have shown that the film properties depend on deposition conditions and preparation techniques. In this work, the optical properties of tungsten oxide thin films prepared in reactive de magnetron sputtering of tungsten target with argon in oxygen atmosphere have been studied. The optical properties of films prepared at different sputtering power (300 - 400) watts and deposition pressure (0.65 ., 0.90) Pa were investigated through the transmittance measurements in the wavelength range 300 - 800 nm. The experimental data were used as an input data for simulations to determine the band gap energy, refractive index, extinction coefficient, and film thickness of tungsten oxide films. From these studies the effects of increasing sputtering power from 300 watts to 400 watts was found to; decreased optical band gap from 3.16 eV to 2.97 eV while refractive index increased from 2.05 to 2.38 respectively. In addition, the deposition rate increased while extinction coefficient decreased with sputtering power. Increasing deposition pressure from 0.65 Pa to 0.90 Pa resulted in the decrease in band gap energy from 2.94 eV to 2.89 eV while refractive index decreased from 2.43 to 2.08 respectively. Further, the X-ray diffraction measurement indicated that tungsten oxide thin films deposited were amorphous. The amorphous nature was confirmed by AFM measurement, which reveals a smooth surface.