Tribenzyltin(IV)chloride Thiosemicarbazones: Novel Single Source Precursors for Growth of SnS Thin Films** By Balasaheb P. Bade, Shivram S. Garje, * Yogesh S. Niwate, Mohammad Afzaal, and Paul O’Brien Tin sulfide (SnS) thin films are deposited using simple tin thiosemicarbazone complexes of the type Bz 3 SnCl(L) (L ¼ thiosemicarbazones of salicylaldehye and 4-chlorobenzaldehyde). Thin films are deposited using aerosol-assisted (AA) CVD in the range 375–475 8C. X-ray diffraction (XRD) shows the formation of SnS regardless of growth temperature and precursor type. Scanning electron microscope (SEM) images show that the films have wafer-like morphology, and the growth temperatures do not have a profound effect on morphology. Keywords: Single-source precursors, Thin films, Tin sulfide, Tin thiosemicarbazones 1. Introduction Many binary tin sulfides (SnS, SnS 2 , Sn 2 S 3 , Sn 3 S 4, Sn 4 S 5 ) are known. [1] Of these, SnS, SnS 2 , and Sn 2 S 3 are the three main discrete phases. SnS and SnS 2 exist in layered structures whereas the mixed valence Sn 2 S 3 has a ribbon structure. The band gaps of SnS and SnS 2 are 1.3 eV and 2.18 eV, respectively. [2,3] The band gap of SnS (1.3 eV) lies between the band gaps of Si (1.12 eV) and GaAs (1.43 eV). [2,3] The materials have been studied as semi- conductors, solar collectors, or photovoltaic materials with high energy conversion. [4,5] A band gap of 1.3 eV makes SnS suitable for applications in holographic recording sys- tems, [6,7] solar control devices, [8] and photovoltaic materials. SnS 2 , with its layered structure, is isostructural with CdI 2 . This permits intercalation of alkali metals [9] and metallo- cenes, [10,11] which can result in an increase in conductivity. Not much attention has been given to tin sulfide thin films as compared to Si or GaAs films. [12,13] Methods such as electroless deposition, [14] spray-pyrolysis, [15] low pressure [16] and plasma-assisted [17] CVD, chemical bath deposition, [18] vapor transport methods, [19] melt growth, [20] etc. have been used for the deposition of SnS thin films. For example, precursors such as SnR 4 (R ¼ Me, Et)/H 2 S/H 2 and SnCl 4 /H 2 S/H 2 have been utilized in low-pressure [16] and plasma-assisted [17] CVD, respectively. However, significant amounts of impurities including chloride, elemental sulfur, etc. have been encountered in the films grown by these methods. The deposition of tin sulfide films from precursors such as [Sn(SCH 2 CF 3 ) 4 ] or [Sn(SPh) 4 ] requires hydrogen sulfide (H 2 S) as an additional sulfur source. [21,22] These precursors on their own do not result in SnS. This was attributed to facile disulfide (RS-SR) elimination, which is due to the presence of non-covalently bonded SS interactions and cis-annular interactions in the molecules like [M(SR) 4 ], where M is a Group IV element. [23] Thermogravimetric analysis and mass spectrometry data showed that [Sn(SR) 4 ] results in RS-SR in the gas phase, supporting the formation of disulfide during the CVD process. [23] However, in the presence of a minimal flow of H 2 S it was possible to deposit SnS films. It is predicted that the sulfur in tin sulfide may be from H 2 S gas and not from the thiolate precursors. [12] Even unsymmetrical tin dithiocarba- mates [12] and tin complexes containing chelating ligands [23] possessing a direct Sn-S bond may or may not form SnS in the absence of H 2 S gas. It was established that chelating thiolate ligands could hinder disulfide elimination. [23] Thus, Parkin et. al. have reported the use of a chelating dithiolato ligand complex, [Sn(SCH 2 CH 2 S) 2 ] for tin sulfide coatings on glass using AACVD. [23] Thiosemicarbazones are versatile S, N donor ligands. Considering the direct metal-sulfur bond in thiosemicarba- zone complexes, we thought it worthwhile to explore the possibility of their use as single-source precursors for depositing metal sulfide thin films. The single-source precursors possess some intrinsic advantages such as improved air/moisture stability, limited pre-reactions, low toxicity, and control over stoichiometry. Their low volatility DOI: 10.1002/cvde.200806687 Full Paper [*] Dr. S. S. Garje, B. P. Bade, Y. S. Niwate Department of Chemistry, University of Mumbai Vidyanagari, Santacruz (East), Mumbai – 400 098 (India) E-mail: ssgarje@chem.mu.ac.in Dr. M. Afzaal, Prof. P. O’Brien The School of Chemistry and The School of Materials, The University of Manchester Oxford Road, Manchester, M13 9PL (UK) [**] The authors thank Dr. Rogers Jarvis for Raman spectra. Thanks are due to SAIF, IIT-Bombay for providing NMR spectra. Financial support from DST, India for a ‘BOYSCAST’ fellowship (SSG), EPSRC (UK) (MA) is gratefully acknowledged. Supporting Information is available online from Wiley InterScience or from the author. 292 ß 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Chem. Vap. Deposition 2008, 14, 292–295