Role of growth conditions on optical and electrical properties of fiber structured Zn_0.90Cd_0.1O thin films

Fiber structured Zn_0.90Cd_0.1O films were obtained on glass substrate using zinc acetate and cadmium acetate solution through chemical spray pyrolysis method. All the deposited films are polycrystalline with hexagonal wurtzite structure. The average crystalline size of the deposited films were estimated through intensity of diffraction peak corresponding (101) plane, which is observed to increase with increase substrate temperature. The films deposited at 673 and 723 K have fibrous structure irrespective of the precursor concentration. The presence of Cd in the deposited films was confirmed by EDAX. The high transparency around 90% in visible region was observed for the sample deposited at 723 K using 0.0125 M concentration. It is seen that the optical energy band gap varies from 2.85 to 3.05 eV as the deposition temperature is changed from 673 to 723 K. The film deposited using 0.05 M concentration had low Urbach energy values compared to other molar concentrations confirming the minimization of defect states in these samples. With increasing deposition temperature the near band edge peak of photoluminescence spectrum shifted towards shorter wavelengths and in the same spectrum the weak green emission may be due to presence of singly ionized oxygen ion. The estimated activation energy of the deposited films was observed to decrease with increasing temperature and precursor concentration.