Enhancement of electrical conductivity of sol–gel doped ZnO films through Zr doping and vacuum annealing

Undoped and Zr doped ZnO thin films were deposited onto the glass substrates using sol–gel spin coating method. A set of deposited films were annealed in vacuum ambience at 350°C, and their structural, optical, electrical, photoluminescence and surface morphological properties are compared with that of the as deposited films. X-ray diffraction patterns showed that all the films fit well with the hexagonal wurtzite structure of ZnO with a preferential growth along the (002) plane. All the films showed high transmittance in the visible region, and the average transmittance is found to be >90%. The electrical resistivity was minimum (4.3 × 10− 3 Ω cm) for the annealed film prepared from starting solutions having Zr doping level of 2 at-%, which is one order of magnitude lower than that of its as deposited counterpart. The photoluminescence and SEM results substantiate the discussion on electrical resistance values obtained.