Metal sulfide thin films by chemical spray pyrolysis

CdS, ZnS and CuS thin films were prepared by spray pyrolysis method using metal chlorides and thiourea (tu) as starting materials. Metal sulfide films form as products of thermal decomposition of complexes Cd(tu)(2)Cl-2, Zn(tu)(2)Cl-2 and Cu(tu)Cl .1/2H(2)O, originally formed in aqueous solution at precursors molar ratio 1:2. The metal-ligand bonding is thermally stable up to 220 degreesC, followed by multistep degradation process of complexes. The TG/DTA analysis show similar thermal behaviour of complexes up to 300 degreesC with the formation of metal sulfides in this decomposition step. In air intensive oxidation processes are detected close to 400, 600 and 720 OC for Cu, Cd and Zn complexes, respectively. The results of thermoanalytical study and XRD of sprayed films show that CdS and ZnS films could be grown at 450 degreesC even in air while deposition of copper sulfide films should be performed in an inert atmosphere. High total impurities content of 10 wt.% in CdS films prepared at 240 degreesC is originated from the precursor and reduced to 2 wt. % by increasing the growth temperature up to 400 degreesC.