Growth of polycrystalline ZnS0.5 Se0.5 films by screen printing technique

Thin films of ZnS_0.5 Se_0.5 have been prepared on glass substrate by screen printing method followed by sintering process using ZnS, ZnSe, ZnCl₂. H₂O and ethylene glycol as a binder. To deposit good quality films, optimum conditions have been determined. The structure, composition and optical properties of these films have been investigated as a function of sintering temperature. The layers grown below 400degC show secondary phases of ZnS, ZnSe and ZnCl₂ in conjunction with a ZnS_0.5 Se_0.5 phase. At growth temperatures above 400degC, all the secondary phases start to disappear favouring the formation of ZnS_0.5 Se_0.5. Polycrystalline ZnS_0.5 Se_0.5 films with a strong (200) orientation were grown at a sintering temperature of 500degC. These layers have the wurtzite crystal structure. The bandgap of these films are determined by reflection spectra in the wavelength range (325 - 600) nm using Tauc relation. These films have a direct band gap. The energy band gap was found to be 2.82 eV for x = 0.5.