A Single Source Approach To Deposition Of Nickel and Palladium Sulfide Thin Films By LP-MOCVD
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M5.16.1
A Single Source Approach To Deposition Of Nickel and Palladium Sulfide Thin Films By LP-MOCVD
J. Waters, P. O’Brien and J.H. Park The Manchester Material Science Centre and Department of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, UK E-mail: [email protected] and [email protected] ABSTRACT Compounds of the type M(S2CNRR’)2, M = Ni(II), Pd(II), RR’ = Et2, MeEt and MenBu, have been synthesized and used as single-source precursors for the fabrication of NiS and PdS thin films via low-pressure (LP) metal-organic chemical vapour deposition (MOCVD). The phase of nickel sulfide films deposited on glass substrates was found to be NiS1.03 or a mixture of NiS1.03 and NiS, whilst palladium sulfide films were only tetragonal PdS. The films have been characterized by X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), transition electron microscopy (TEM) and energy dispersive analysis of X-rays (EDAX). INTRODUCTION In the last decade there has been a significant increase in interest in metal sulfide materials that have potential for use in the electronics industry or photovoltaic applications [1]. Nickel sulfide has a band gap of ca. 0.5 eV [2], which confers potential for use as a thermophotovoltaic converter [3]. Palladium sulfide had a band gap of ca. 2.0 eV [4] and has been used widely in catalysis [5-7]. There are relatively few reports on the deposition of nickel or palladium sulfide thin films from single-source precursors by CVD. Cheon et al. [4] have reported deposition of stoichiometric NiS and PdS from both thermal and photochemical CVD routes using M(S2COCHMe2)2, M = Ni or Pd and Nomura et al. studied the deposition of NiS1.03 from Ni(S2CNEt2)2 on Si(111) at 350 - 400 oC by LP-MOCVD [8]. Thin films of PdS were deposited on GaAs substrates by LP-MOCVD of Pd(S2CNMenHex)2 [9] Stoichiometric NiS has previously been deposited by pulsed laser ablation [10]. Work has also been reported on the deposition of nickel sulfide films by chemical bath deposition (CBD) techniques. Hexagonal NiS has been deposited by successive ionic layer adsorption and reaction (SILAR) technique [2]. Nickel sulfide thin films were also prepared from solutions of nickel sulfate and thioacetamide in an alkaline medium [11] and from acidic solutions of sodium thiosulfate [12]. In a recent study, films and powders of various phases of nickel sulfide were prepared by soft solution methods [13]. In our recent work, a number of metal dialkyl dithiocarbamate complexes have been utilised for the preparation of metal sulfide thin films or as nano-sized particles [14, 15]. In this paper, we report the deposition of nickel sulfide and palladium thin films from single-source precursors of the type M(S2CNRR’)2 where RR’ = Et2, MeEt, MenBu.
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EXPERIMENTAL The precursors, Ni(S2CNEt2)2 (1), Ni(S2CNMenBu)2 (2), Pd(S2CNEt2)2 (3), Pd(S2CNMeEt)2(4) and Pd(S2CNMenBu)2 (5), were synthesised by reaction of the metal(II) chloride with the sodium salt of the dithiocarbamate, Na+(S2CNRR’)-, (RR’ = alkyl) [
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