Composite formation in CdSe:Cu(2)Se nanocrystal films, charge transport characteristics and heterojunction performance

The use of nanocrystals as materials for potential technological applications depends on tailoring their properties through intentional doping with external impurities. We have used a new technique to synthesize nanocrystal thin films of CdSe:Cu(2)Se containing different weight percentages (wt%) of Cu(2)Se. The films were deposited on glass substrates at room temperature by co-evaporation of CdSe and Cu(2)Se powder in nitrogen gas at a pressure larger than that required for conventional thin film deposition. The films consisted of nanograins of CdSe doped with Cu(2)Se (i.e., nanograins of Cd(1−x)Cu(2(x))Se where x is the atom% of Cu(2)Se doped into CdSe) for lower wt% of Cu(2)Se, and nanocomposites of Cd(1−x)Cu(2(x))Se and Cu(2)Se for higher wt% of Cu(2)Se. An energy band diagram built using the Anderson model was used for discussing the heterojunction characteristics of the junction between nanograins of Cd(1−x)Cu(2(x))Se and Cu(2)Se. To investigate the usefulness of the nanocrystal thin films of CdSe:Cu(2)Se for practical applications, the I–V characteristics of p–p and p–n hetero-junctions formed by the films respectively with nanostructured films of similarly deposited Cu(2)Se and CdSe films were studied.