Effect of the composition and annealing on the electron transport in ZnxCd1-xSe nanocrystalline films

Nanocrystalline layers of ZnxCd1-xSe with five different compositions in the range x = 0.39-0.8 were prepared by thermal vacuum evaporation and alloying of ZnSe and CdSe sublayers with various nominal thicknesses (0.12, 0.25 or 0.37 nm). Temperature dark and photocurrent measurements were carried out in the range 77-423 K to explore the effect of annealing at 473 K and 673 K on the dark and photoconductivity of the films. A gradual decrease of the conductivity and photoconductivity of the films annealed at 473 K has been observed with increasing Zn content while the dark current activation energy has increased. However for the films annealed at 673 K the compositional variation of both dark and photoconductivity has displayed a deep minimum for the x = 0.59 films. The obtained results have been discussed considering the effect of the sublayer nominal thickness and the intergrain barriers on the electron transport in the films and keeping in mind that the film surface of the annealed films is quite smooth. It has been inferred that the annealing increases the density of Se vacancies and reduces the compositional disorder and the interface defect density. (C) 2013 Elsevier B.V. All rights reserved.