Effect of Sr doping on structural, morphological, optical and electrical properties of spray pyrolized CdO thin films

Abstract

Cadmium oxide (CdO) and strontium (Sr) doped cadmium oxide (SCO) thin films have been fabricated onto glass substrate by spray pyrolysis technique. The CdO and SCO films have been deposited at 350 °C substrate temperature and their structure, morphology, optical, electrical properties have been investigated & analyzed as a function of Sr-concentration (0–4 mol%). X-ray diffraction analysis confirms that the films are polycrystalline and they have cubic structure and shows preferential growth in (200) plane. The average grain size of the films has been found 22.23 nm. SEM image reveals that the undoped film has rock like morphology and the morphology significantly changes with Sr-doping concentration. Results of optical properties show that optical transmittance, refractive index and extinction coefficient changes markedly with Sr doping. As the doping concentration of Sr increases from 0 to 4%, the band gap value decrease from 2.67 to 2.49 eV and the Urbach energy increases. Temperature dependent electrical resistivity indicates that all the films possess poor metal like behavior. The Hall measurement confirms that both doped and undoped CdO films are n-type semiconductor.