Purifying VO2 phase synthesized by sol-gel method via annealing process

Abstract

Vanadium dioxide (VO2) film has significant interesting phase transition properties called metal-semiconductor transition (MST) which occurs at 68 °C. This transition behavior makes it suitable for various applications, including thermochromic materials for smart windows, sensors, and electronics devices. In this study, we aimed to focus on the purification of VO2 through the sol-gel synthesis method from vanadium alkoxide (VO(OC3H7)3. To analyze the effects of annealing temperature (500 °C-600 °C) on the resulting structural, morphology, and electrical properties, x-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), temperature dependent resistance, and infrared (IR) thermal image were considered. The resistance as a function of the temperature shows an abrupt change confirming the phase transition. However, XRD shows an impurity of other vanadium oxides such as V6O13. In addition, the sample annealed at 600 °C shows a non-uniform surface filled with island clusters, while the sample annealed at 500 °C has a smooth and uniform surface. Raman spectra further supports the formation of VO2 (M) clusters mixed with V6O13 in smooth area, resulting in a decrease in electrical properties, significant reduced resistance change at the excessive annealing temperature.