Photo conductive response in vacuum-deposited unalloyed and alloyed thin films of some metal oxides

Thin films of tin oxide, alloyed with antimony have been grown on glass substrate with varying thicknesses and substrate temperature using electron beam evaporation method. In similar manner, a few thin films using indium oxide alloyed with antimony have also been prepared. These films were annealed to improve their electrical conductivity and optical transmission. XRD spectra of a few samples revealed mixed phases of the oxides with different orientation of lattice planes. The transmittance and reflectance data of these films were used to first compute absorption coefficient (alpha) and then to estimate the optical band gap. The optical band gaps are found to lie in the range of 3 eV corresponding to extreme lower wavelength of VIS range and the films had good optical transmission (similar to 80 %) over VIS range. Based on this knowledge, a suitable violet lamp (lambda : 185-320 nm) was used to radiate the prepared thin films and the photo current generated was measured with sensitive electrometer. The variation of current with time has been measured both on application and withdrawal of incident radiation. The fast and slow carrier life time have been calculated to obtain photo current gain and maximum 3dB band width. The results have been discussed in term of deposition parameters and alloying