Phase transition of ultrasonically sprayed VOx thin films: The role of substrate temperature

Abstract

In this study, vanadium oxide (VOx) semiconductor films were deposited on glass substrates using ultrasonic spray pyrolysis technique. The effect of the substrate temperature on the physical properties of the deposited thin films was investigated. For this purpose, 0.05 M VCl3 aqueous solutions were prepared and sprayed on glass substrates at different temperature of 225 degrees C, 275 degrees C, 325 degrees C and 375 degrees C. Structural properties of VOx thin films were investigated by taking xray diffraction (XRD) patterns and it was determined that the films deposited at 225 degrees C and 275 degrees C have tetragonal V4O9 phase while the ones deposited at 325 degrees C and 375 degrees C have mixture of alpha-V2O5 and beta-V2O5, alpha-V2O5 being dominant. The optical band gap energies of the films were determined to be in the range of 2.29 eV to 2.42 eV. Electrical investigations revealed that VOx films have n-type conductivity and electrical resistivity decreased from 4.07 Omega cm to 0.67 Omega cm depending on the increase in substrate temperature. Scanning electron microscopy (SEM) images showed that morphology of the films highly is sensitive to substrate temperature.