Effect of Substrate Temperature on the Structural, Optical and Electrical Properties of DC Magnetron Sputtered VO2 Thin Films

This study focuses on the effect of the substrate temperature (T-S) on the quality of VO2 thin films prepared by DC magnetron sputtering. T-S was varied from 350 to 600 degrees C and the effects on the surface morphology, microstructure, optical and electrical properties of the films were investigated. The results show that T-S below 500 degrees C favors the growth of V2O5 phase, whereas higher T-S (>= 500 degrees C) facilitates the formation of the VO2 phase. Optical characterization of the as-prepared VO2 films displayed a reduced optical transmittance (T similar to) across the near-infrared region (NIR), reduced phase transition temperature (T-t), and broadened hysteresis width (Delta H) through the phase transition region. In addition, a decline of the luminous modulation (Delta T similar to lum) and solar modulation (Delta T similar to sol) efficiencies of the as-prepared films have been determined. Furthermore, compared with the high-quality films reported previously, the electrical conductivity (sigma) as a function of temperature (T) reveals reduced conductivity contrast (Delta sigma) between the insulating and metallic phases of the VO2 films, which was of the order of 2. These outcomes indicated the presence of defects and unrelaxed lattice strain in the films. Further, the comparison of present results with those in the literature from similar works show that the preparation of high-quality films at T-S lower than 650 degrees C presents significant challenges.