The Use of Xanthates as Precursors for the Deposition of Nickel Sulfide Thin Films by Aerosol Assisted Chemical Vapour D
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The use of Xanthates as Precursors for the Deposition of Nickel Sulfide Thin Films by Aerosol Assisted Chemical Vapour Deposition P.L. Musetha,a N. Revaprasadua M.A Malikband P.O’Brienb a
Department of Chemistry, University of Zululand, Private Bag X 1001, KwaDlangezwa,3886, South Africa. b The School of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL. E-mail – [email protected]
ABSTRACT Nickel sulphide (NiS) thin films have been deposited on glass by aerosol assisted chemical vapour deposition(AACVD) using single source precursors of the type, ([Ni(S2COR2)2], R = C2H5 or C3H7). TGA analyses showed that the precursors are highly volatile, making them suitable for AACVD studies. As deposited NiS films were polycrystalline as confirmed by XRD. The films have been characterised by xray diffraction (XRD), scanning electron microscopy (SEM), and Energy dispersive analysis of x-rays (EDAX). INTRODUCTION The deposition of metal sulfide thin films has attracted considerable attention due to their use in many and diverse application. Nickel sulfide has been studied because of it’s potential as a transformation toughening agent for materials used in semiconductor applications.1 Its use as catalysts and coatings for photogalvanic cells have also been reported.2 The existence of various compositions of nickel sulfide including: Ni3+xS2, Ni3S2, Ni4S3+x, Ni6S5, Ni7S6, Ni9S8, NiS, Ni3S4 and NiS2 makes the such studies both interesting and challenging.3 Nickel sulfide thin films has been prepared using chemical vapour deposition,4,5 chemical bath deposition,6,7 and electrodeposition. 8 Particles of nickel sulfide have been synthesized by solid-state reactions9 and precipitation from aqueous10 and organic solutions.11 Cheon et. al.5 have reported the deposition of NiS by both a thermal and photochemical CVD using [Ni(S2COCHMe2)2]. O’Brien et. al.4 have recently reported the deposition of binary nickel sulfide films from various alkyl dithiocarbamate derivatives of nickel using low-pressure metal-organic chemical vapour deposition technique. The films were shown to be predominantly composed of wires of NiS nanowhiskers which have also been reported from the reaction of a nickel substrate with sulfur in ethylenediammine.9 Nanorods and nanoprisms of NiS have been synthesized using a solventless thermolytic decomposition of a nickel thiolate precursor in the presence of octanoate, which serves as a capping agent.12 A by-product of the reaction under certain conditions is colloidal Ni3S4 in the form of misshapen needles. The thermolysis of nickel alkyl xanthates in octylamine at mild temperatures yielded a mixture of rod and spherical NiS particles. In this paper we report the deposition of NiS thin films from single-source precursors using nickel ethyl/iso-propyl xanthate, [Ni(S2COR2)2], R = C2H5 or C3H7).
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EXPERIMENTAL DETAILS Precursor synthesis All reactions were carried out at room temperature. Reagent grade solvents were used without further purification. The starting materials as
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