Structural, Morphological, And Optical Properties Of W-Doped Vo2 Thin Films Prepared By Sol-Gel Spin Coating Method

Thermochromic VO2 thin films were deposited on soda-lime glass via sol-gel method. Doping was done through adding tungstic acid solution to the vanadium solution precursor. Grazing incidence x-ray diffractometer (GIXRD) results showed that VO2 and V6O13 phases were formed together in the heat-treated sample. According to the GIXRD result of the W-doped sample, only VO2 remained. Field-emission scanning electron microscopy (FESEM) micrographs showed that the VO2 grain size decreased from about 70 to about 25 nm for undoped film and 2 wt% W-doped films, respectively. Atomic force microscopy (AFM) results showed that the root mean square roughness for the film with 180 nm thickness was about 18 nm, and 2 wt% W-doped film had a smoother surface. Diffuse reflectance spectroscopy (DRS) results showed that the band gap energy for undoped, 1 wt% W- doped, and 2 wt% W-doped VO2 thin films was 1.7, 1.3, and 0 eV, respectively. Four-point probe resistivity measurements showed a significant decrement, from approximately 1 M omega at 15 degrees C to NIR spectroscopy results, maximum optical transmission for undoped and W-doped films was approximately 75% and 35%, respectively.