The Effect of Opto-Electronic Transition Type on the Electric Resistivity of Cr-Doped Co3O4 Thin Films

Abstract

Cr-doped Co3O4 thin films were prepared by spray pyrolysis on soda-lima glass. The structure and morphology of the prepared samples were characterized by grazing incidence X-ray diffraction (GIXRD), Fourier-transform infrared spectroscopy (FTIR) and Scanning electron Microscopy (SEM). The results indicated the formation of a single cubic spinel phase with a crystallite size of about 6 nm. Different electronic transitions and estimations of the band gap structure were determined from the optical absorption spectra. The dependence of electrical resistivity on Cr content was investigated. It was found that the resistivity increased by increasing the Cr content. In addition, the effect of photon excitation on the electrical properties showed that the electrical resistivity decreased under visible illumination (λvis. = 532 nm) and increased under infrared illumination (λIR = 780 nm). The relative change in resistivity (sensitivity) under both light illuminations was enhanced by increasing the Cr content. Therefore, this work introduces a new application for Co3O4 material as a light detector.