VO2–WO3 nanocomposite thin films synthesized by pulsed laser deposition technique

Pure VO2 and VO2–WO3 composite thin films were grown on quartz substrate by pulsed laser deposition (PLD) technique. The influence of varying WO3 molar concentration in the range from x = 0.0 to x = 0.4 on structural, electrical and optical properties of VO2–WO3 nanocomposite thin films has been systematically investigated. X-ray diffraction studies reveal the single crystalline monoclinic VO2 phase (m-VO2) up to 10% of WO3 content whereas both m-VO2 as well as h-WO3 (hexagonal WO3) phases were present at higher WO3 content (0.2 ≤ x ≤ 0.4). Optical transmittance spectra of the films showed blue shift in the absorption edge with increase in WO3 content. Temperature dependence of resistivity (R–T) measurements indicates significant variation in metal–insulator transition temperature, width of the hysteresis, and shape of the hysteresis curve. Cyclic Voltammetry measurements were performed on VO2–WO3 thin films. A direct correlation between V/W ratio and structure–property relationship was established. The present investigations reveal that doping of WO3 in VO2 is effective to increase the optical transmittance and to reduce the semiconductor to metal phase transition temperature close to room temperature.