Optical and Electrical Properties of Nanostructured CdSe-Cu2Se Thin Films
Department of Nanoscience and Nanotechnology, University of Kerala, Kariavattom Campus, Thiruvananthapuram-695 581, Kerala, India
Abstract: We report the deposition of CdSe-Cu2Se nanostructured thin films and study of their optical and electrical properties.
Nanostructured CdSe-Cu2Se thin films were deposited on glass substrates by thermal evaporation of CdSe and Cu2Se powders for different weight % (wt%) of Cu2Se. Oxidation states of Cu in the samples were determined using XPS. Absence of satellite peaks of Cu2+ ruled out possibility for existence of copper in Cu(II) oxidation state. From XRD results together with EDS analysis, it was inferred that Cu2Se got incorporated into CdSe lattice for low wt %, while for higher wt %, Cu2Se existed as a separate phase in the samples. The particles seen in the AFM images showed clear decrease in size with increase in the Cu2Se wt %. Micro-Raman spectra showed the existence of electron-phonon coupling in the samples. UV-Vis spectra of the samples were analyzed to study the variation of the band gap of the samples with wt % of Cu2Se. The activation energy obtained from electrical conductivity measurements decreased with increase in the wt % of Cu2Se. The electrical conductivity of the samples was analyzed in detail. The photocurrent in the CdSe-Cu2Se nanostructured films increased with increase in the wt % of Cu2Se.