Influence of deposition parameters on the optical properties of thin tungsten oxide films prepared by reactive Dc magnetron sputtering
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Date
2008-11
Authors
Wangati, C. K.
Njoroge, W.K.
Okumu, J.
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Abstract
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.
Description
This article was scanned from a hard copy journal
Keywords
deposition conditions, optical properties, thin films, Tungsten oxide
Citation
East African Journal of Physical Sciences volume 8 part 1