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 ºC are amorphous and contain thermal decomposition residues of Zn(tu)2Cl2. Chlorine content becomes negligible at 500 ºC, carbon and nitrogen in the form of zinc cyanamide are present in a trace amount up to 540 ºC. Highly (002) orientated ZnS films with wurtzite structure and closely stoichiometric composition could be grown at temperatures close to 500 ºC 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 (∼25 nm) and slightly Zn-rich composition at 500 ºC. Higher temperature (530 ºC) 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 ºC. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)