VO_2-WO_3 nanocomposite thin films synthesized by pulsed laser deposition technique

摘要

Pure VO_2 and VO_2-WO_3 composite thin films were grown on quartz substrate by pulsed laser deposition (PLD) technique. The influence of varying WO_3 molar concentration in the range from x =0.0 to x=0.4 on structural, electrical and optical properties of VO_2-WO_3 nanocomposite thin films has been systematically investigated. X-ray diffraction studies reveal the single crystalline monoclinic VO_2 phase (m-VO_2) up to 10% of WO_3 content whereas both m-V02 as well as h-WO_3 (hexagonal WO_3) phases were present at higher WO_3 content (0.2 ≤ x≤0.4). Optical transmittance spectra of the films showed blue shift in the absorption edge with increase in WO_3 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 VO_2-WO_3 thin films. A direct correlation between V/W ratio and structure-property relationship was established. The present investigations reveal that doping of WO_3 in VO_2 is effective to increase the optical transmittance and to reduce the semiconductor to metal phase transition temperature close to room temperature.