Synthesis and characterization of tungsten oxide wo3 nanostructures thin films for gas sensing applications
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Date
2018-02
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University of Zululand
Abstract
This work presents the synthesis of a room temperature gas sensor based on tungsten oxide (WO3) thin films. The synthesis of WO3 thin films was carried out using a direct current (DC) reactive magnetron sputtering at different deposition temperatures (300, 400 and 500 ºC). The deposition time, pressure, power, oxygen and argon flow rates were kept constant. The purpose of this work was to investigate the effect of deposition temperature on WO3 based sensor film and to see if the deposition temperature can be optimised in order to improve the gas sensing properties of WO3 thin films. The scanning electron microscope (SEM) equipped with energy dispersive x-ray spectroscopy (EDS) was utilized to study the surface morphology and chemical composition or stoichiometry of all samples. The results from the SEM images showed that as the deposition temperature changes, the morphology of WO3 film also changes. X-ray diffraction (XRD) was then used to study the crystal structure of the samples and the samples were found to be amorphous at 300 ºC and polycrystalline at 400 ºC and 500 ºC. It was also observed from XRD that the change in deposition temperature resulted in the formation of different phases and orientations in WO3 films since WO3 film deposited at 300 ºC found to be amorphous, at 400 ºC it was hexagonal in crystal structure, and WO3 film deposited at 500 ºC was found to be tetragonal. When using Scherre’s equation it was found that as the temperature increases, the grain size of the samples also increases. The atomic force microscopy (AFM) was then used to study the roughness of the samples. The AFM revealed that as the deposition temperature increases the roughness of the samples also increases. Rutherford backscattering spectrometry (RBS) was used to study the composition and thickness of the samples. RBS confirmed that the samples deposited were WO3. It was found that as the deposition temperature increases the thickness of the thin films also increases. The gas sensing properties of the samples were investigated using the gas sensor apparatus (Kenosistec) at room temperature and it was found that increasing the deposition temperature from 300 ºC to 500 ºC enhanced the gas sensing properties of the samples.
Description
A dissertation submitted in fulfilment of the requirements for the Degree of Master of Science for the Department of Physics and Engineering, Faculty of Science and Agriculture at the University of Zululand, 2018.
Keywords
Tungsten oxide wo3 nanostructures, Gas sensing applications