Structural and tribological properties of tungsten oxide thin film on a silicon substrate

In this work, tungsten oxide thin films are deposited on silicon substrates using the hot filament chemical vapor deposition system. The influence of substrate temperature on the structural, morphological, and elemental composition of the tungsten oxide thin films is investigated using X-ray diffraction, field-emission scanning electron microscopy, and X-ray photoelectron spectroscopy techniques. Also, the mechanical and tribological properties of these thin films are considered using nanoindentation and scratch tests. Based on X-ray diffraction results, it can be concluded that tungsten oxide thin films are synthesized with a cubic WO(3)structure. From field-emission scanning electron microscopy images, it can be seen that tungsten oxide thin films are made of crystal clusters which have grown vertically on the substrate surface. In addition, the results exhibit two asymmetric W4d(5/2)and W4d(7/2)peaks which can be assigned to W(5+)and W(4+)species, respectively. The mechanical results show that the hardness and the elastic modulus increase on raising the substrate temperature up to 600 degrees C. From the tribological performances, the friction coefficient of the tungsten oxide thin film decreases on increasing the substrate temperature.