Effect of precursor medium on structural, electrical and optical properties of sprayed polycrystalline ZnO thin films

The polycrystalline ZnO thin film was deposited on the soda-lime glass substrate using chemical spray pyrolysis technique. Different types of precursor solutions were used for the film preparation. We studied the variations in structural, electrical and optical properties of the samples due to the change in concentration of propanol and ethanol in the precursor solutions. All the films had (0 0 2) plane orientation. Texture co-efficient, grain size and lattice parameters have been calculated. Grain size, optical transmission and electrical conductivity of the films enhanced with the increase in both the types of alcohol concentration. The films exhibited luminescence in two regions – ‘near band edge emission’ (NBE) (∼380 nm) and ‘blue-green emission’ (∼503 nm). Intensity of the blue-green emission varied with percentage as well as type of alcohol used in the precursor solution and from this study we could confirm that the oxygen antisite levels were reduced very much in samples prepared using solution containing higher percentage of alcohol, leading to the reduction of electrical resistivity. The lowest resistivity of 2 × 10−2 Ω cm was obtained for the samples prepared using spray solution having water and propanol in 1:1 volume ratio.