Structural, optical and electrical studies on sol–gel deposited Zr doped ZnO films

Transparent and conducting films of mixed oxides of zinc and zirconium have been prepared by sol–gel method. The amount of zirconium have been varied in between 0 to 3 at.%. XRD patterns showed that the nature of films are polycrystalline but the preferred orientation changes from (1 0 0) to (1 0 1) and finally (0 0 2) with increasing amount of Zr doping. The morphology and crystallite size of the films are strongly dependent on the doping concentration. The resistivity decreases with doping concentration up to 1.5 at.% but increases with concentration more than that. The maximum carrier concentration is (∼1019 cm−3) and the mobility is minimized at this doping concentration. The optical bandgap was estimated from the reflectance and transmittance spectra. The obtained optical bandgap is about 3.3 eV, for unstrained ZnO but slight shrinkage in bandgap is noticed up to 2 at.% doping. There is corresponding rise in width of band tail which is a measure of the disorder in the system.