The use of metal complexes to deposit metal chalcogenide thin films and nanoparticles
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Date
2006
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Abstract
This thesis consists of four chapters. The first chapter describes the properties, methods of deposition and applications of semiconductors. The second chapter focuses on the deposition of metal chalcogenides thin films from single molecular precursors of the type [M {N(EPR2)2}2], were M = Pt, Pd, Ni; E = S or Se and R = fPr or Ph. Ligands of the type R2P(E)NP(E)R2, where R = *Pr or Ph were prepared to synthesize these precursors. Single X-ray structures of fP^NfP^PSe^h] and [Pd{N(SPh2)2}2] are reported and discussed. The X-ray structure of the platinum complex shows a square-planar conformation whereas the six membered PtSe2P2N ring adopts a distorted "boat" conformation.
The third chapter describes the deposition of metal sulphide thin films from [M(S2COR)2], were M = Pt, Pd, Ni, Cd, Co, Cu and R = Et or dPr. Single X-ray structures of [M(S2COR)2j M = Pt, Pd, and Ni, R = Et are reported and discussed. The NiS thin films are polycrystalline and their 0 values are in good agreement with the literature values. The phases do not seem to be affected by temperature whereas the morphology of the films changes with temperature. The morphology of the films has been found to be greatly influenced by varying the temperature. All the ligands and precursors were characterised by elemental analysis and by using spectroscopic techniques such as infrared (IR), mass spectrometry (MS), proton and carbon nuclear magnetic resonance (*H and !3C NMR). Thin films of PtSea, Pt, PdSe2, PaUSe, Pdi7Sei5, PdS, and PdS2 were deposited by aerosol assisted chemical vapour deposition (AACVD) and low pressure metal-organic vapour deposition (LP-MOCVD) using metal complexes of irninobis(dialkylphosphinato)dichalcogenide ligands. Thin films of NiS, CdS, Pt, PdS, Pdi6S7, and CogSg were deposited by AACVD using the respective metal xanthate complexes. The films were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX).
The fourth chapter focuses on the preparation of nanoparticles and nanorods from cadmium complexes. The synthesis of CdS nanoparticles and nanorods are described in detail. The synthetic route used for the synthesis of the CdS nanoparticles is the thermolysis of metal complexes, [Cd(S2CNMe2)2] and [Cd{-SC(=S)OCH(CH3)2}4], in tri-octylphosphine oxide (TOPO) and hexadecylamine (HDA). The optical properties of the nanoparticles were studied by using ultraviolet (UV)-visible and photoluminescence (PL) spectroscopy. There were blue shifts in the band gaps for all CdS samples; however, photoluminescence was very poor. The hexagonal phase of CdS was observed for all CdS samples using XRD measurements. The transmission electron microscopy (TEM) images show that the TOPO capped CdS nanoparticles have a spherical shape whereas the HDA capped particles are rod shaped. Nanoparticles of CdS were characterised by UV-vis, PL, XRD and TEM.
Description
A thesis presented to the Department of Chemistry, University of Zululand in fulfilment of the requirement for the award of the Degree of Doctor of Philosophy in Chemistry, 2006.
Keywords
Organometallic compounds, Complex compounds, Metal complexes