ZnS thin films deposited by spray pyrolysis technique

ZnS thin films were prepared by spray pyrolysis technique using aqueous solutions of zinc chloride and thiourea at molar ratio of 1: 1, 1:2 and 2:1. The films were characterized by XRD, FTIR, SEM and EDX. The phase composition, structure and morphology of sprayed films are controlled by both, the substrate temperature and the precursors molar ratio in the solution. The films deposited below 380 degrees C are amorphous and contain thermal decomposition residues of Zn(tu)(2)Cl-2. Chlorine content becomes negligible at 500 degrees C, carbon and nitrogen in the form of zinc cyanamide are present in a trace amount up to 540 degrees C. Highly (002) orientated ZnS films with wurtzite structure and closely stoichiometric composition could be grown at temperatures close to 500 degrees C using Zn:S molar ratio of 1:2 in spray solution. The film consists of well-shaped hexagonal prisms with size of 100 nm. The spray of equimolar solution (Zn:S = 1:1) results in ZnS films with smaller grain size (similar to 25 nm) and slightly Zn-rich composition at 500 degrees C. Higher temperature (530 degrees C) is needed to grow the films with wurtzite structure. The use of Zn-rich (Zn/S > 1) solution results in the films consisting of ZnO and ZnS phases above 400 degrees C. (c) 2005 WILEY-VCH Verlag GmbH Z Co. KGaA, Weinheim.