Optical and structural properties of evaporated Zn_xCd_1-xS (0 ≤ x ≤ 1) thin films

ZnCdS is a potential candidate for the application as window layer in solar cells. Co-evaporation of CdS along with known quantities of ZnS is a simple route to deposit Zn_xCd_1-xS (0 ≤ x ≤ 1) thin films. We have taken this route and deposited the thin films at room temperature in a working pressure of the order of 10^-6 torr. Effect of annealing temperature and composition on the structural, optical and electrical properties has been investigated in detail. Hexagonal (Wurtzite) crystal structure is observed for 0 ≤ x ≤ 0 5 whereas zinc-blende for x ≥ 0 6. Direct band gap varies in the range 2.5-3.3 eV for the as-deposited films, whereas for annealed films the band gap is found to be in the range 2.25 eV to 3.17 eV. Lattice constant decreases and the band gap increases with the increase in x values showing linear trend in both cases.