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

This study focuses on the effect of the substrate temperature (T) on the quality of VO₂ thin films prepared by DC magnetron sputtering. T was varied from 350 to 600 °C and the effects on the surface morphology, microstructure, optical and electrical properties of the films were investigated. The results show that T below 500 °C favors the growth of V₂O₅ phase, whereas higher T (≥500 °C) facilitates the formation of the VO₂ phase. Optical characterization of the as-prepared VO₂ films displayed a reduced optical transmittance (T˜) across the near-infrared region (NIR), reduced phase transition temperature (T), and broadened hysteresis width (ΔH) through the phase transition region. In addition, a decline of the luminous modulation (ΔT˜lum) and solar modulation (ΔT˜sol) efficiencies of the as-prepared films have been determined. Furthermore, compared with the high-quality films reported previously, the electrical conductivity (σ) as a function of temperature (T) reveals reduced conductivity contrast (Δσ) 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 lower than 650 °C presents significant challenges.