Thermal decomposition of thiourea complexes of Cu(I), Zn(II), and Sn(II) chlorides as precursors for the spray pyrolysis deposition of sulfide thin films

Comparative study on thermal decomposition of four thiourea-metal complexes , solid precursors for spray pyrolysis deposition (SPD) methods, had been c arried out by using thermoanalytical and X-ray diffraction (XRD) methods in combination. [Cu-2(tu)(6)]Cl-2. 2H(2)O (1), ZnCl2(tu)(2) (2), Sn2Cl4(tu)(5 ). 2H(2)O (3), and SnCl2(tu) (4) prepared from aqueous thiourea (tu) soluti ons, had been decomposed in a simultaneous thermogravimetric/differential t hermoanalytical (TG/DTA) apparatus, while XRD phase analysis of solid resid ues obtained at various temperatures had been performed. In static air, a m ain degradation step between 200 degreesC and 300 degreesC led to the forma tion of Cu9S5 (digenite), ZnS (zinc blende), and SnSz (berndtite), respecti vely. Unfortunately, some chemical species with low volatility still remain ed in condensed phase, while above 400 degreesC, primary oxidation products of sulfides such as Cu2O(SO4) (dolerophanite), ZnO, and SnO2 also occurred . Nevertheless, intermittent spray pyrolysis depositions of Cu2SnS3 and Cu2 ZnSnS4 films from some thiourea solutions with Cu(I), Zn(II), and Sn(II) on to glass substrates, with temperature ranging between 225 degreesC and 300 degreesC, were successful. (C) 2001 Elsevier Science B,V, All rights reserv ed.