Optical and electrical investigations of tungsten trioxide for optoelectronics devices

This study aimed to investigate the properties of WO3 thin films deposited on glass and silicon substrates using the thermal spray technique. The films were prepared with a WO3 concentration of 10 mM and a deposition temperature of 350 & DEG;C. Different numbers of spray cycles ranging from 3 to 39 were applied. The X-ray diffraction analysis revealed that the crystal structure of the WO3 films exhibited a monoclinic phase, with a preferred orientation along the (hkl) (200) direction, which varied with the number of sprays. Field emission scanning electron microscopy images showed an increase in grain size with the number of sprays, ranging from 30.14 nm to 39.4 nm. Energy-dispersive X-ray spectroscopy (EDX) analysis indicated that the stoichiometry of the WO3 films was optimized at 12 spray cycles and a substrate temperature of 350 & DEG;C. The atomic ratio of tungsten to oxygen was found to be 26-74%, resulting in a W/O ratio of 2.84. Atomic force microscopy (AFM) images displayed varying average roughness values and root mean square values across different numbers of sprays, ranging from 19.73 to 49.74 nm and 25.85 to 54.76 nm, respectively. The Ultraviolet-Visible properties of the WO3 films demonstrated an absorption edge at a wavelength of 320 nm, which decreased at longer wavelengths. The energy gap of the films decreased from 3.63 to 2.98 eV, while the Urbach energy (Eu) increased from 0.455 to 2.639 eV. Electrical conductivity and activation energy (Ea) measurements were conducted under optimal conditions, resulting in a conductivity of 3.449 x 10(-7) (& omega; cm)(-1) and an activation energy of 0.214 eV.