There is much interest in the electronic potential of ‘nano’-semiconductors. The avenue of research pursued in this project was in inorganic analogues of graphene, namely metal chalcogenides MxEy (M = metal, E = S, Se, Te, x ≠ y = integer value). Thin films of these materials have been used in solar cells, ambient thermoelectric generators and IR detectors, due to their interesting properties, such as: optoelectronics, magnetooptic, piezoelectric, thermoelectric and photovoltaic, as well as electrical conductivity. The key issues with the use of these materials are the formation of controlled films, especially in terms of stoichiometry, crystallinity and uniformity, and also the precursor system used. The aim of this research was to synthesise and isolate novel precursor compounds for use in the deposition of metal sulfide thin films (for use with molybdenum and tungsten). The potential viability of the compounds as single source precursors (ssp) was judged following ThermoGravimetric Analysis (TGA). The compounds were also subjected to analysis using NMR (1H, 13C and 31P where applicable), infrared and UV-Vis spectroscopy, as well as elemental analysis. Cadmium sulfide (CdS) is one of the key direct band gap II-VI semiconductors, having vital optoelectronic applications for laser light-emitting diodes, and optical devices based on non-linear properties. The ratio of these films should ideally be 1:1, however, during the formation of cadmium sulfide films, particularly at elevated temperatures, a common problem encountered is the production of sulfur deficient films. These films have a formula consistent with 〖Cd〗_x S_y, where x is an integer value greater than y, but the sulfur deficiency is generally no greater than 10 %. In order to correct this sulfur deficiency, it was decided to investigate deposition making use of both a ssp and an additional sulfur source, with the aim of producing uniform films with 1:1 Cd:S.Molybdenum disulfide films have been deposited previously from multi source precursors and more recently using ssp. In this project MoS2 was deposited using novel ssps in both LP and AACVD on a variety of substrates with the aim of producing uniform thin films and assessing any differences in the morphology of the deposition. This work was continued with the deposition of WS2 and MoxW1-xS2 from ssps which had not been reported previously. The films deposited were analysed using XRD, SEM, EDX (when available) and Raman spectroscopy.

Metal chalcogenides (sulfides, selenides and tellurides) are materials of current interest due to their peculiar properties such as optoelectronic, magnetooptic, thermoelectric and piezoelectric displays. These semiconducting materials have potential applications in solar cell devices, infrared detectors and ambient thermoelectric generators. Previously, these materials have been deposited by multiple-source precursor route with several problems associated with this technique. This work describes the synthesis of metal complexes (Zn, Cd, Fe, Ni, Pd, Pt) using the imidodichalcogenodiphosphinate ligand (Woollins ligand). Their thermal decomposition together with structural and spectroscopy analysis was carried out. The complexes were used as single source precursors for the deposition of cadmium selenide, cadmium phosphide, cadmium sulfide, zinc selenide, iron selenide and the tellurides of nickel, palladium, platinum and iron as thin films and powders. These were deposited by AACVD and pyrolysis. The deposited thin films and powders were characterised by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), energy dispersive analysis of X-rays (EDAX), X-ray photoelectron spectroscopy (XPS) and superconducting quantum interference device (SQUID). The cadmium complexes [Cd{iPr2P(Se)NP(Se)iPr2}2] and [Cd{iPr2P(S)NP(Se)iPr2}2] deposited the mixture of hexagonal CdSe and monoclinic Cd2P3 films at the flow rate of 160 sccm at 475 and 500 °C. At the flow rate of 240 sccm, only hexagonal CdSe was deposited from [Cd{iPr2P(Se)NP(Se)iPr2}2] at all temperatures. Hexagonal CdS and the mixture of orthorhombic Cd6P7/cubic Cd7P10 were deposited from [Cd{iPr2P(S)NP(S)iPr2}2]. The zinc complexes [Zn{iPr2P(Se)NP(Se)iPr2}2] and [Zn{iPr2P(S)NP(Se)iPr2}2] both deposited cubic ZnSe at all temperatures with the flow rates of 160 and 240 sccm. The iron complexes [Fe{(SePPh2)2N}2] and [Fe{(SePPh2NPPh2S)2N}2] deposited orthorhombic FeSe2 mixed with monoclinic Fe3Se4 by pyrolysis at 500 and 550 °C. An unresolved pattern was observed from the complex [Fe{(SePPh2NPPh2S)2N}2] at 550 °C. XPS analysis of the deposited FeSe2 showed the surface oxidation of the material, while the magnetic measurements on the sample using SQUID confirmed its ferromagnetic properties. The telluride complexes of nickel, palladium, platinum and iron deposited the metal telluride respectively as: hexagonal NiTe, hexagonal PdTe, hexagonal PtTe2 (mixed with rhombohedral PtTe) and hexagonal FeTe2. Conductivity studies on NiTe and PdTe revealed them to be insulators, while the magnetic measurements on FeTe2 indicated its antiferromagnetic behaviour.

Thesis (PhD (Chemistry and Polymer Science))--Stellenbosch University, 2008. / The successful preparation and structural characterization of a number of N,N-dialkyl-N’-benzoyl(thio)selenourea ligands is described; where the intermolecular interactions are characterized by the presence of Resonance Assisted Hydrogen Bonding (RAHB), π- π interactions between neighbouring benzene residues only being evident amongst the longer alkyl chain derivatives. The first structural characterization of an asymmetrically substituted N,N-dialkyl- N’-benzoylselenourea ligand reveals an increased stability of the Z isomer in the solid state, this being reflected by the sulfur analogue. Attempts to synthesise N,N-dicyclohexyl-N’-benzoylselenourea led to the isolation and structural characterization of a novel 1,3,5-oxaselenazine salt and dicyclohexylaminobenzoate. The first structural characterization of a “bipodal” N,N-dialkyl-N’-benzoylselenourea ligand, 3,3,3’,3’-tetrabutyl-1,1’- isophthaloylbis(selenourea), reveals RAHB in the crystal lattice similar to that exhibited by the “monopodal” analogue, N,N-dibutyl-N’-benzoylselenourea. The successful complexation of the N,N-dialkyl-N’-benzoyl(thio)selenourea ligands to a number of different transition metal ions is reported allowing the preparation of several potential single source precursors. Coordination through the O and Se/S donor atoms to Pd(II) results in the formation of square planar metal complexes, with a cis conformation, several of which could be structurally characterized. In particular, the first structural elucidation of an asymmetrically substituted N,N-dialkyl-N’-benzoylselenourea metal complex, cis-bis(N-benzyl-N-methyl-N’- benzoylselenoureato)palladium(II) indicates the increased stability of the EZ isomer in the solid state. Structural elucidation of the novel (N,N-diphenyl-N’-benzoylselenoureato)cadmium(II) reveals a bimetallic complex in the solid state, where the expected 2:1 ligand : metal ratio is maintained, and the two Cd(II) centres are 5 and 6 coordinated, with O and Se donor atoms. Multinuclear Nuclear Magnetic Resonance (NMR) Spectroscopy has been employed in the thorough characterisation of the potential single source precursors, 77Se NMR spectroscopy indicating a decreased shielding of the 77Se nucleus as the “hardness” of the central metal ion increases i.e. Pd(II) > Zn(II) > Cd(II). Use of 113Cd NMR spectroscopy indicates the preferential binding of N,N-diethyl-N’- benzoylselenourea to Cd(II) over that of its sulfur analogue, and initial studies suggest a form of chelate metathesis taking place in solution. 31P NMR spectroscopy is used to gain insight into the formation of cis-bis(N,N-diethyl-N’- benzoylselenoureato)Pt(II). Thermolysis of (N,N-diethyl-N’-benzoylselenoureato)cadmium(II) and its sulfur analogue led to the successful synthesis of CdSe and CdS quantum dots respectively, where thermolysis over a range of temperatures allows a degree of size control over the resulting nanoparticles. The effect of precursor alkyl chain length on nanoparticle morphology was investigated for both the N,N-dialkyl-N’-benzoylthio- and –selenoureas. A correlation between the two for the (N,N-dialkyl-N’-benzoylselenoureato)Cd(II) complexes is described and possible growth mechanisms are discussed. Preliminary investigations into the use of other N,N-dialkyl-N’-benzoyl(thio)selenourea metal complexes as single source precursors reveal that both (N,N-diethyl-N’-benzoylselenoureato)Zn(II) and its sulfur analogue show potential as single source precursors for the formation of ZnO and ZnS nanoparticles respectively. Initial studies into the use of N,N-dialkyl-N’-benzoyl(thio)selenourea metal complexes as single source precursors for the synthesis of core-shell nanoparticles is briefly described. The Aerosol Assisted Chemical Vapour Deposition (AACVD) of several N,N-dialkyl-N’-benzoyl(thio)selenourea metal complexes is reported, where both (N,N-diethyl-N’-benzoylselenoureato)Cd(II) and its sulfur analogue allow the deposition of crystalline CdSe and CdS respectively. The AACVD of (N,N-diethyl-N’- benzoylselenoureato)Zn(II) leads to the deposition of crystalline ZnSe, ZnS being deposited by (N,N-diethyl-N’-benzoylthioureato)Zn(II). The deposition of heazelwoodite (Ni3S2) with varying morphologies results from the AACVD of cis-bis(N,N-diethyl-N’-benzoylthioureato)Ni(II). Thermal annealing of the amorphous material deposited by the AACVD of cis-bis(N,N-diethyl-N’-benzoylthioureato)Pd(II), allows the formation of highly crystalline palladium. The deposition of metallic platinum using cis-bis(N,N-diethyl-N’-benzoylthioureato)Pt(II) is described as well as the deposition of crystalline Pd17Se15 from cis-bis(N,N-diethyl-N’-benzoylselenoureato)Pd(II). This, to the best of our knowledge, is the first time that AACVD has been performed, using the N,N-dialkyl-N’- benzoyl(thio)selenourea metal complexes as single source precursors, in addition, we believe it to be the first time that palladium selenide has been deposited using the AACVD technique.

xx, 153 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / In the research area of Group 13 hydroxide clusters, progress is often hampered by difficult and inefficient synthetic procedures. This has greatly limited the numerous potential applications of Group 13 hydroxide compounds, many of which require large amounts of material. Most relevant to this dissertation is their application as precursors for high quality amorphous metal oxide thin films. Addressing this issue, this dissertation presents a series of Group 13 containing hydroxide compounds of general formula [M 13 (μ 3 -OH) 6 (μ-OH) 18 (H 2 O) 24 ](NO 3 ) 15 which are generated through an efficient, scalable synthetic procedure. Throughout this dissertation, the compounds are generally referred to by their metal content, i.e. [Ga 13 (μ 3 -OH) 6 (μ-OH) 18 (H 2 O) 24 ](NO 3 ) 15 is designated as Ga 13 . Chapter I reviews the literature of inorganic and ligand-supported Group 13 hydroxide compounds with the aim of identifying common structural trends in metal composition and coordinating ligands. This summary is limited to clusters of aluminum, gallium, and indium. Chapter II describes in detail the synthesis and characterization of one such cluster, Al 13 . Following this in Chapter III is the description of the first heterometallic Group 13 hydroxide compound, Ga 7 In 6 , which along with Ga 13 was used as a precursor material for metal oxide thin films in collaboration with Professor Doug Keszler at Oregon State University. Chapter IV describes a series of six Ga/In compounds, as well as two Al/In compounds. Included in this chapter is an analysis of the heat-induced decomposition properties of the Ga/In clusters. Understanding such thermal decomposition is particularly relevant for the use of these compounds as precursor materials, as an annealing step is used to condense the films. Chapter V addresses the potential for post-synthetic modification of the compounds through metal and ligand exchange reactions, an area that also addresses the issue of solution stability of the structures Chapter VI describes the synthesis and characterization of related Group 13 compounds, including two infinite chain structures and additional heterometallic compounds. Lastly, Chapter VII concludes this dissertation and discusses potential areas of future research. This dissertation includes co-authored material and previously published results. / Committee in charge: Victoria DeRose, Chairperson, Chemistry; Darren Johnson, Member, Chemistry; James Hutchison, Member, Chemistry; Michael Haley, Member, Chemistry; Raghuveer Parthasarathy, Outside Member, Physics