Solid State Ionics, Vol.141-142, 439-446, 2001
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 carried 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) solutions, had been decomposed in a simultaneous thermogravimetric/differential thermoanalytical (TG/DTA) apparatus, while XRD phase analysis of solid residues obtained at various temperatures had been performed. In static air, a main degradation step between 200 degreesC and 300 degreesC led to the formation of Cu9S5 (digenite), ZnS (zinc blende), and SnSz (berndtite), respectively. Unfortunately, some chemical species with low volatility still remained 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 Cu2ZnSnS4 films from some thiourea solutions with Cu(I), Zn(II), and Sn(II) onto glass substrates, with temperature ranging between 225 degreesC and 300 degreesC, were successful.
Keywords:thin sulfide films;spray pyrolysis deposition;thermal decomposition;simultaneous TG/DTA;XRD;thiourea-metal complexes;Cu9S5;SnS2;ZnS;Cu2O(SO4);Cu2SnS3;Cu2ZnSnS4