APPLIED ORGANOMETALLIC CHEMISTRY Appl. Organometal. Chem. 2005; 19: 59–67 Materials, Nanoscience and Catalysis Published online in Wiley InterScience (www.interscience.wiley.com). DOI:10.1002/aoc.833 Cadmium O-alkylxanthates as CVD precursors of CdS: a chemical characterization Davide Barreca 1 *, Alberto Gasparotto 2 , Cinzia Maragno 2 , Roberta Seraglia 1 , Eugenio Tondello 2 , Alfonso Venzo 1 , Venkata Krishnan 3 and Helmut Bertagnolli 3 1 ISTM-CNR and INSTM, Department of Chemical Sciences, Padova University, Via Marzolo, 1-35131 Padova, Italy 2 Department of Chemical Sciences, Padova University and INSTM, Via Marzolo, 1-35131 Padova, Italy 3 Institut f ¨ ur Physikalische Chemie, Universit ¨ at Stuttgart, Pfaffenwalding 55, D-70569 Stuttgart, Germany Received 7 April 2004; Accepted 8 August 2004 Cadmium bis(O-alkylxanthates) are potential single-source molecular precursors for the chemical vapor deposition (CVD) of Cd(II) sulfide thin films. In this work, a multi-technique characterization of Cd(O-RXan) 2 compounds [where O-RXan is CH 3 CH 2 OCS 2 (O-EtXan) or (CH 3 ) 2 CHOCS 2 (O- i PrXan)] is performed by means of several analytical methods (extended x-ray absorption fine structure, Raman, Fourier transform infrared and optical absorption, spectroscopics 1 H and 13 C NMR, thermal analysis and mass spectrometry) for a thorough investigation of their structure and chemical–physical properties. The most important results concerning the chemical behavior under different experimental conditions, with particular attention to relevant properties for CVD applications, are presented and discussed. Copyright  2004 John Wiley & Sons, Ltd. KEYWORDS: cadmium(II) bis(O-alkylxanthates); CdS; characterization; EXAFS; NMR; mass spectrometry INTRODUCTION Cadmium sulfide (CdS), a direct band-gap material (E g = 2.4 eV), 1,2 has been employed extensively in thin-film transis- tors, X-ray detectors and photodiodes 3 and n-type window layers for solar cells. 4–6 For such applications, the system properties have been tailored by controlled modifications of the crystal structure 7,8 and morphology, 9 exploiting the ver- satility of suitable bottom-up synthetic routes. In this context, chemical vapor deposition (CVD) has attracted much atten- tion as a possible method for the production of thin-film optoelectronic devices under mild and controlled condi- tions. A major role in tailoring material properties resides in a proper choice of the molecular precursors, whose nature strongly affects the composition, the microstruc- ture and the morphology of the final product. In partic- ular, single-source precursors containing all the elements to be deposited in a unique molecule 10,11 can be used conveniently as building-blocks for the single-step trans- formation of molecules into materials. The use of similar compounds offers significant advantages with respect to *Correspondence to: Davide Barreca, ISTM-CNR and INSTM, Department of Chemical Sciences, Padova University, Via Marzolo, 1-35131 Padova, Italy. E-mail: barreca@chin.unipd.it multiple-source reagents, such as a better film purity and an easier control of stoichiometry. Moreover, the material structure may be preformed already in the precursors by a suitable design of their molecular architecture. Examples of single-source precursors employed for the CVD of cad- mium sulfide films include tris(alkyl)chalcogenophenolato complexes such as Cd(SC 6 H 2 t Bu 3 ) 2 12 and dialkyldithio- carbamates [Cd(S 2 CNRR ′ ) 2 ], where R and R ′ are alkyl groups. 11,13 – 15 The present work is part of an extensive research activity in the CVD of metal sulfide thin films (ZnS, CdS, Zn x Cd 1−x S) from single-source O-alkylxanthate precursors. 16 – 18 Such compounds have been used previously in various fields, such as agents in metallurgy, accelerators in rubber vulcanization and high-pressure lubricants. 19,20 Nevertheless, to the best of our knowledge, cadmium(II) xanthates have not been employed as CVD precursors to date. In this paper we describe the most relevant results concerning the synthesis and characterization of bis(O-ethyl) and bis(O-isopropyl) cadmium xanthates Cd(O-EtXan) 2 and Cd(O- i PrXan) 2 , where O-EtXan is CH 3 CH 2 OCS 2 and O- i PrXan is (CH 3 ) 2 CHOCS 2 . In addition to their appreciable volatility and stability to air and moisture, the presence of pre-formed Cd–S bonds and the absence of Cd–C bonds enable their clean conversion into cadmium(II) sulfide in an Copyright  2004 John Wiley & Sons, Ltd.