Electrical Conducting Behavior of W- Doped VO2 Thin Films / La0.5Sr0.5CoO3Heterostructure

W-doped vanadium oxide thin films were obtained by sol-gel spin coating process on the pre-heat treated silicon wafer. The precursor for thin film coating is prepared with vanadium methanol solution. These films were post annealed at 580oC for 30 min under controlled air pressure. The average thickness of the films was about 60 nm. The predominant phase of the films is monoclinic VO2 from Raman spectra analysis. These thin films exhibit a metal-semiconducting transition. The transition temperature was lowered from 68oC to 34oC by doping with tungsten cation with 15%W. A heterostructure was made by stacking the VO2 films on the La0.5Sr0.5CoO3 (LSCO) thin films. The LSCO thin film of about 300nm thickness was obtained by r.f. magnetron sputtering deposition process. An apparent rectifying behavior was observed for a p-n junction of VO2/La0.5Sr0.5CoO3 (LSCO). The reverse bias current is characterized by a reverse threshold voltage of ~4.2V at 40oC and decrease to ~3V at 80oC. The rectifying properties show temperature dependence under the metal-semiconducting transition of VO2.