Electrochemical synthesis of n type ZnS layers on p Cu2O/n ZnO heterojunctions with different deposition temperatures
Metal oxide p n heterojunctions consisting of p Cu2O/n ZnO/n ZnS nanostructures were deposited on an ITO substrate by three step electrodeposition. The effect of ZnS layer deposition temperature on the properties of the heterojunction was investigated by different techniques. The Mott Schottky analysis confirmed the n type conductivity for ZnO and ZnS and p type conductivity for the Cu2O layer, respectively. Also, it showed a decrease of ZnS donor concentration with increasing deposition temperature. The X ray diffraction (XRD) analysis confirms a pure phase of hexagonal ZnO, cubic ZnS and cubic Cu2O structures, respectively. The heterojunction with ZnS deposited at 60 degC shows high crystallinity. The morphological measurements by scanning electron microscopy (SEM) indicate that the deposition temperature has a significant influence on the morphology of ZnO and the atomic force microscopy (AFM) images revealed the improvement of Cu2O morphology by increasing the ZnS deposition temperature. The UV Vis response shows strong absorption in the visible region and the profile of optical absorption spectra changes with the ZnS deposition temperature. The current voltage (I V) characteristics of the Au/p Cu2O/n ZnO/n ZnS/ITO heterojunction display well defined rectifying behavior for the heterojunction with ZnS deposited at 60 degC.