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Self-assembled metal-organic materials have been championed as candidates for the next generation of functional materials. This has been attributed to their ‘bottom-up’ design and preparation, error-checking mechanisms, chemical tuneability, and novel functionality arising from the metal centres. This thesis proposes subcomponent self-assembled metallopolymers as a new and accessible class of material designed towards electronic and light-emitting applications. The metallopolymers are comprised of conjugated imine-based ligand strands that are helically wrapped around a linear array of closely spaced Cu atoms. To date, their development has been faced with several synthetic challenges. Moreover, the absence of methodologies to characterise and control the structures of these metallopolymers prevents their rational design towards performing a specific function. Remarkably, their charge-transport properties – perhaps the most interesting feature of these metallopolymers – have yet to be reported. The work presented in this thesis seeks to explore methods to characterise and rationally tailor the structure of iminopyridine-based self-assembled metallopolymers and, for the first time, elucidate the charge-transport properties of this class of material. We have designed a novel bifunctional monomer unit which polymerises in the presence of Cu¹ to afford long helical metallopolymers (>75 repeat units). We identify and develop techniques to control the length, regiochemistry and stereochemistry of the two helical strands and determine the effect that these three structural parameters have on the electronic properties of the metallopolymers. By controlling these structural properties, the polymerisation mechanism of this type of helical metallopolymer is elucidated, allowing the design of tailored metallopolymers. Electronic properties, including electrical conductivity, are investigated, noting anisotropic charge-transport through the metallopolymer and resistive switching behaviour. Finally, we employ the metallopolymer as a self-assembled scaffold, controlling the aggregation state of appended fluorophores, and thus modulating their photophysical properties. With several new design rules and behaviours for this class of metallopolymer in hand, we anticipate that the work presented in this thesis will fuel future studies towards creating the next-generation of metallopolymers for studying circularly polarised light emission and resistive switching applications.

This investigation is based on the topochemical modification of three set of phases: Sr3Co2O5Cl2, SrO(Sr(Ru0.5M0.5)O3)n (M = Ti, Mn, Fe; n = 1, 2, ∞), and SrO(SrVO3)n (n = 1, 2, ∞). The topochemical reduction of Sr3Co2O5Cl2 using sodium hydride as a solid state reducing agent results in the formation of a reduced phase containing cobalt centres with an average oxidation state of +2 and an overall composition of Sr3Co2O4Cl2. The resulting material adopts a structure containing double sheets of square-planar corner-sharing CoO2 units separated by rock salt SrCl layers. Variable-temperature diffraction measurements reveal that these sheets undergo a cooperative Jahn-Teller distortion at T ~ 200 K due to unevenly filled degenerate (dxy, dyz) orbitals. This material adopts a magnetic structure in which the moments within each sheet are ordered antiferromagnetically, but the sheets are aligned ferromagnetically. An investigation was carried on the reduction behaviour of Ru-doped Sr(RuxFe1-x)O3. It was found that the reduction was non-topochemical for values of x > 0.5. For values of 0 < x < 0.5, no single phase precursor material could be formed. For the material with x = 0.5, reduction with CaH2 produced a new phase with composition Sr(Ru0.5Fe0.5)O2. This material is the first reported instance of Ru2+ in an extended transition metal oxide. DFT calculations reveal that, while the iron centres adopt a high-spin configuration, the ruthenium centres are in an intermediate-spin S = 1 configuration. Resulting competing magnetic interactions lead to frustration and lack of ordering. In order to further study the reduction behaviour of extended transition metal oxides containing ruthenium, the reduction of Sr2(Ru0.5Fe0.5)O4 and Sr3(Ru0.5Fe0.5)2O7 was performed using CaH2 as a solid state reducing agent. In these cases, reduction leads to segregation of the materials into multiple phases adopting closely related structures that differ mainly in their oxygen content. In these materials, the ruthenium centres are preferentially reduced, such that starting from materials containing Ru5+ and Fe3+, materials containing Ru(3-δ)+ and Fe3+ are produced. Similarly, the low-temperature oxidation using CuF2 as a solid state fluoride source was performed on materials with composition Sr3(Ru0.5M0.5)2O7 (M = Ti, Mn, Fe). In the case of M = Mn and Ti, materials with composition Sr3(Ru0.5Fe0.5)2O7F2 are produced in which the ruthenium centres are oxidised to Ru6+. For the M = Fe material, oxidation results in partial exchange of O for F and a material with composition Sr3(Ru0.5Fe0.5)2O5.5F3.5 in which the ruthenium centres are oxidised from +5 to +5.5 while the iron centres remain in a +3 oxidation state. While fluorination of the M = Ti leads to increasing itinerant electronic behaviour, fluorination of the M = Mn and Fe materials induces a twisting of the MX6 octahedra that enables magnetic order to emerge at low temperatures. Finally, reaction of the SrO(SrVO3)n (n = 1, 2, ∞) series of phases with CaH2 results in the formation of phases with composition SrO(SrVO2H)n (n = 1, 2, ∞), the first examples of stoichiometric oxyhydride materials. SrVO2H is magnetically ordered at room temperature, while the n = 1 and n = 2 materials order at 170 K and 240 K respectively. The high magnetic ordering temperature arises from strong interactions between (dxy, dyz) orbitals in a manner analogous to the reduced iron-containing phases SrO(SrFeO2)n.

This dissertation described the synthesis and characterization of various conductive metal–organic frameworks. The systematic investigation of changes in the electronic structure of these frameworks as a function of metal ion or unit cell charge provides insights into the mechanism of charge transport in metal–organic materials and new design principles for the synthesis of frameworks with specific electronic or magnetic properties. Chapter 1 provides a general introduction to the challenges associated with engineering charge transport in metal–organic materials. The design strategies for accessing high conductivities are discussed, and benchmark materials for each design strategy are provided. The biggest remaining questions facing the field are outlined, illustrating the need for improved systematic and mechanistic studies.Chapter 2 describes the synthesis of a series of layered frameworks containing early, first row transition metal ions and redox-active ligands. The combination of vibrational and electronic spectroscopy and magnetic susceptibility measurements reveal differing degrees of metal-to-ligand electron transfer across the series. These electron transfers cause the magnetic properties to switch from frustrated antiferromagnetism for titanium to ferrimagnetism for chromium. Further, the charge transport properties of these materials are shown to correlate with the energy alignment of metal and ligand orbitals, suggesting this is the critical factor for optimization in the design of new frameworks.Chapter 3 describes the electrochemical characterization of a layered iron framework containing redox-active ligands. The electrochemical capacity of this framework is shown to rival those of transition metal oxides. This capacity is further shown to be unique amongst frameworks of this structure type, where other metal ion congeners display half the capacity of the iron framework. Spectroscopic characterization demonstrates that close matching of metal and ligand redox potentials is critical to this boosted capacity, providing a new design principle for framework-based cathodes.Chapter 4 describes the synthesis of niobium and molybdenum frameworks containing redox-active ligands. The use of metal-to-ligand electron transfer to generate rare frameworks based on second-row metal ions is demonstrated. Despite being isoelectronic, these frameworks are shown to possess different electronic structures, with the niobium phase being nearly insulating while the molybdenum phase is highly conductive. Solution-phase exfoliation of the molybdenum phase is demonstrated, illustrating its potential as a new 2D material.Chapter 5 describes detailed spectroscopic and magnetic characterization of a framework containing one dimensional chains of iron ions as a function of reduction. The reduction is shown to unexpectedly possess substantial azolate character. Magnetic properties reveal that the mixed-valent frameworks show signatures of itinerant ferromagnetic interactions at high temperature, creating a Griffiths phase at room temperature with a cluster spin glass ground state. The observation of special behavior near half and full reduction suggests the possibility of more exotic electronic phenomena.

Strong electron correlations in transition metal oxides give rise to the emergence of a diverse array of transport phenomena and emergent phases such as quantum criticality, nematic order, and magnetism. The synthesis of thin films of these materials using molecular beam epitaxy (MBE) has enabled the discovery of additional phases that are not observed in bulk crystals. Furthermore, the precision offered by MBE over layer thickness in the growth of heterostructures and subtle modifications of the lattice imposed by epitaxial strain open the possibility of tuning these phases. The central aim of the work in this thesis is to explore the relationships between the strongly correlated transport phenomena and emergent phases and the structure of the MBE-grown crystal. This includes tilting and connectivity of the oxygen octahedra in the perovskite structure, quantum well thickness, epitaxial strain, and proximity effects. The thesis begins with an introduction to the physics of metallic transport in correlated materials with an emphasis on highlighting the phenomena that have been observed in the MBE-grown materials discussed in this work. This includes pseudogap behavior in the density of states, quantum criticality, non-Fermi liquid transport, and Van Hove singularities in the electronic structure. This is followed by an overview of the specific perovskite materials and the hybrid MBE growth technique used to synthesize them. The body of the experimental work in this thesis is comprised of two main parts. First, investigations of the electron correlations in RTiO3/SrTiO3/RTiO3 (R = Gd, Sm) quantum wells will be discussed. This includes tunneling spectroscopy experiments in which tunnel junction devices were fabricated to the pseudogap phase that emerges in the two-dimensional electron gas residing in the well. A robust quadratic dependence of the Hall angles in these quantum wells is discussed. The second part focuses on the transport properties of the layered strontium ruthenate Ruddlesden-Popper series. A novel method of growing these materials incorporating the use of the volatile precursor RuO4 is introduced. Finally, a study of the electronic and magnetic properties of an epitaxially strained Sr3Ru2O7 film is discussed, where it was found that slight perturbations of the lattice greatly enhance the emergent ordered phases. The thesis concludes with a brief summary and proposals for future research in correlated oxides.

Diluted magnetic semiconductor (DMS), which possesses both semiconducting and magnetic properties, is one of candidates to fulfil the requirement for the new generation spintronics devices. The magnetism in DMS originates from the exchange splitting that displaces the spin-up and spin-down electrons of dopants in Fermi energy level. However, the driven force of this splitting remains unclear. Using first principles calculations, we have studied the electronic and magnetic properties and thermal stabilities of several different DMS materials. Alkaline elements doping, rare earth doping, and transition-metal (TM) doping have been introduced into the DMS host for achieving magnetic interactions. In this project, native defects, doping defects and defect complexes are considered to study the properties and the origins of the possible magnetism. Intrinsic ferromagnetism is found in ZnO doped with Na, K, and Sm. The magnetism in Na and K doped ZnO is originated from the O 2p hole states around Zn vacancies. However, in samarium doped ZnO, it originates from the 4f electrons of Sm. The ferromagnetism can be stabilized by forming different defect complexes. In case of the TM doped monolayer MoS2, Co, Fe, Mn, and Ni can induce magnetism via p-d hybridization between the TM and surrounding Mo and S atoms. However, the magnetic moment is strongly dependent on the type and concentrations of the dopants. In TM doped monolayer black phosphorous, magnetism is observed in systems doped with V, Cr, Mn, Fe and Ni, which mainly attributes to the d orbitals of substitutional TMP. Magnetization can be stabilized and slightly enhanced by forming defect complex (TMP+VP) compared to single TMP. Similarly, magnetism is observed in monolayer SnO doped with TM from V to Co due to the p-d interaction between the TM dopants and the surrounding Sn/O atoms. The results show that TMsub and defect complex (TMsub +VO) have the same magnetic moment; while the magnetic moments of (TMsub +VO) vary significantly. In summary, our theoretical investigations illustrate that DMS materials can be fabricated by doping with different elements, and the magnetic coupling can be tuned through defects engineering. These findings can be very instructive for future DMS fabrication and applications.

Nanostructures have been lauded for their quantum confinement capabilities and potential applications in future devices. Compound semiconductor nanostructures are being integrated into the next generation of photovoltaic and light emitting devices to take advantage of their unique optical characteristics. Despite their promise, adoption of nanostructure based devices has been slow. This is due in large part to difficulties in effective fabrication and processing steps. By manipulating the surface energy of various components during growth, we can control the final structure and corresponding optoelectronic characteristics. Specifically I will present on GaSb quantum dots embedded in GaAs and GaAs nanowires using novel substrate and catalyst materials. GaSb quantum dots embedded in a GaAs matrix are ideal for devices that require capture of minority carriers as they exhibit a type II band offset with carrier concentration in the valence band. However, during GaAs capping, there is a strong driving force for the dot to demolish into a distribution of intact dots, rings, and GaSb material clusters. We demonstrate the ability to mitigate this effect using both chemical and kinetic means: we alter the surface chemistry via the addition of aluminum, and use droplet epitaxy as an alternative quantum dot formation method. Secondly, the growth of high quality GaAs on silicon has always been restricted due to material incompatibilities. With the emergence of increasingly smaller low power electronics, there is a demand to integrate optoelectronic devices directly on the surface of CMOS sensor stacks. Utilizing the vapor-liquid-solid growth mechanism we are able to demonstrate the growth of high quality GaAs nanowires on polycrystalline substrates at low temperatures. This allows for the growth of III-V nanowire based devices directly on the metal pads of pre-packaged CMOS chips. We also investigate the potential use of bismuth as an alternative to gold for catalyzing nanowire growth.

Conducting metallopolymers (CMPs) have been extensively studied due to their potential for various applications in sensing, catalysis, light-emitting diodes, and energy harvesting and storage. The incorporation of metal centers into conjugated organic polymer backbones not only makes these materials multi-functional, but also changes the properties, such as electroactivity and conductivity. In this work, we aim to take advantage of the direct electronic interaction between metal centers and polymer backbones in these metallopolymers to make novel materials that could be used for photovoltaic and spintronic applications. Furthermore, a fundamental study on the interactive role of transition metals in conducting metallopolymers has been conducted, which could help to provide insights for the rational design of metallopolymers for certain applications. Charge transfer in hybrid photovoltaics is often inhibited by the capping ligands on inorganic semiconductors. To bypass the ligand effect, my study was focused on preparing a conducting metallopolymer, in which metal ions are directly bound to the conjugated organic backbone. These metal ions will serve as nucleation or seed points upon which the inorganic semiconductor can grow directly within the polymer matrix. This fabrication method provides materials with direct bonds between the inorganic semiconductor and the conducting polymer backbone and therefore results in direct electronic communication between the donor and acceptor. With this material, the charge transfer limited by capping ligands could be overcome and can result in highly efficient devices when utilized in solar cells. Besides the efforts to harvest energy form renewable resources, changing the way that we use energy (e.g., in lighting and information storage) could also help to reduce our energy demand. The bistability offered by spin-crossover (SCO) complexes has resulted in sustained research interest due to potential applications in molecular electronics such as memory storage. Interested in making memory devices with a bottom up approach, we have designed and prepared CMPs that are not only conductive but also possess spin-crossover behavior. The novelty of this study lies in the fact that spin-switching could be possibly obtained by changing the oxidation states of metal centers, which could be done at room temperature, offering a new method for spin switching compared to conventional methods for SCO such as in thermal-induced spin transition. To study the charge delocalization and charge transport in CMPs, a series of conducting polymers of Schiff-base ligands and metal complexes have been prepared and characterized. Our successful syntheses of ligand polymers allows for full characterization and direct comparison of these polymers to the corresponding metal-containing polymers, from which the role of the metal centers is elucidated. The effects of conjugation length on electrochemical and spectroscopic properties are also investigated and discussed.

The unique properties of metal-oxide semiconductors make them well suited to a variety of optoelectronic applications. Metal oxides comprise all industrially-relevant transparent conductors (TCs), and there is significant interest in their development as photovoltaic (PV) absorbers, light-emitting diodes, and electrodes in photoelectrochemical (PEC) devices. TCs are heavily-doped, wide-bandgap semiconductors that must simultaneously exhibit high conductivity and high optical transparency across (and beyond) the visible spectral range, but such materials face severe fundamental tradeoffs between transparency and conductivity that preclude the use of TCs in a number of applications that require infrared and near-infrared transparency. High-mobility TC materials such as CdO can acheive a better balance of transparency and conductivity, but their short-wavelength transparency is limited by a low intrinsic direct bandgap of 2.2 eV. This dissertation explores how the properties of CdO can be tuned by bandgap engineering and doping and discusses their use in TC and photoelectrochemical applications. Alloys of the structurally-mismatched endpoint compounds CdO--ZnO have attracted considerable interest within the field of oxide bandgap engineering as they allow the bandgap of ZnO (3.3 eV) to be tuned across the visible range with the incorporation of Cd into hexagonal ZnO. Little is known about the properties of cubic alloys based on Zn in CdO, however. The correlated structural, optical, and electrical properties of CdxZn1-x thin film alloys (0xZn1-x alloys are determined by three complementary techniques: ion-irradiation-induced pinning of the Fermi level at the Fermi-level stabilization energy, X-ray photoelectron spectroscopy, and soft X-ray absorption and emission spectroscopy. The three techniques find consensus in explaining the origin of compositional trends in the optical-bandgap narrowing upon Cd incorporation in wurtzite ZnO and widening upon Zn incorporation in rocksalt CdO. The conduction band minimum is found to be stationary for both wurtzite and rocksalt alloys, and a significant upward rise of the valence band maximum accounts for the majority of these observed bandgap changes. These band alignment details, combined with the unique optical and electrical properties of the two phase regimes, make CdxZn1-x alloys attractive candidates for PEC water splitting applications. A proposed device structure of a CdxZn1-xO-Si tandem PEC is presented.Finally, the unique electrical properties and doping behavior of CdO are examined using simulations based on the amphoteric defect model. The calculated doping and mobility limits are compared with experimental values for Ga-doped CdO.

The broad aim of this dissertation is to develop an atomic scale understanding of the magnetic and electronic properties of double perovskites, a class of materials that hold a lot of promise to realize new multifunctional devices. We have used first-principles density functional theory (DFT) calculations to develop this understanding. In the first section, we focus on double perovskites with half metallic properties. We begin with the most widely studied half metallic double perovskite, Sr2FeMoO6. Even after more than a decade of extensive research, it has not yet been possible to realize the high degree of spin-polarization that has been theoretically predicted in Sr2FeMoO6. We find point defects to be playing a major role in degrading its half metallic properties. We determine transition-metal antisites and oxygen vacancies to be the thermodynamically stable defects, and predict Mo-rich Sr2FeMoO6 and stoichiometric Sr2FeMoO6 with antisite disorder to have poor spin-polarization.We have then used our understanding of the magnetic interactions that result due to antisites disorder in Sr2FeMoO6 to predict Ca2MnRuO6 as a material which should allow high levels of spin-polarized conduction, even in a complete disordered form.Next, we have studied the magnetic interactions in a recently discovered double perovskite Sr2CoOsO6, where the two magnetic ions Co and Os order independently of each other, a behavior that has never been observed in any other magnetic material. By calculating the strength of exchange interactions between different pairs of magnetic ions in the compound, we attribute the observed magnetic behavior to the weak nearest neighbor Co-O-Os interactions compared to the stronger Co-O-Os-O-Co and Os-O-Co-O-Os interactions. We explain this weak Co-O-Os interaction to be due to the small overlap of the Co 3d and Os 5d orbitals.In the next section, we apply the method of determining the chemical potential of the constituent elements in multicomponent systems, which we had developed to calculate the stable defects in Sr2FeMoO6, to a simpler binary semiconductor InP and expand it into a more rigorous and general theory, which we found had been missing in the literature when we examined the point defects in Sr2FeMoO6. After identifying the stable neutral defects in both stoichiometric and non-stoichiometric InP, we determine their defect level within the experimental band gap, using a combination of computationally fast traditional exchange-correlation functionals used in DFT, which underestimate the experimental band gap, and computationally expensive but more accurate hybrid functionals. We combine the neutral-defect formation energies with the position of the defect states and suggest a method to calculate both, chemical potentials of the constituent elements, and the formation of energies of charged defects, as a function of the Fermi level.In the final section, we suggest a method to study the electronic properties of interfaces, which is general enough to address the common questions at interfaces between complex materials such as e.g. found in semiconductor systems or complex oxide heterostructures. Using wurtzite AlN/GaN interface as a test system, we calculate the band line-up and interface charge density due to spontaneous and piezoelectric polarization, using a combination of first principles real-space band structure and electrostatics. Using this method, we show the interface charge density in the AlN/GaN system to be independent of the layer thicknesses of the two materials, with their value being identical to the interface charge density calculated using bulk constants.

Organic Light Emitting Diodes (OLEDs) based on the principle of electroluminescence, constitute a new and exciting emissive display technology for flat panel displays. In order to attain high quantum efficiency for electroluminescence, it is necessary to achieve three attributes: efficient charge injection from the electrodes at low drive voltage, good charge balance, and confinement of the injected charge carriers within the emitting layers. The purpose of this research work was to fabricate, measure and analyze OLEDs based on these fundamental principles using different cathode materials, injection layers and buffer layers in order to determine the best possible configuration. Starting from a simple bi-layered device, multilayered heterojunction OLEDs were built by employing energy band engineering. Since it was the first time that these imaging devices were being built in our Laboratory, developing tools and techniques to get reproducible OLEDs was a prerequisite to the realization of this goal. Thus, through this process, the Lab's capability was realized from the fabrication and characterization perspective, and fundamental knowledge regarding the operation of OLEDs was gained. The OLEDs fabricated were of high efficiency and brightness, and their properties match well with the published literature.

The unsaturated organoboron heterocycles 1,2-oxaborolides, 1,2-dihydro-1,2-oxaborines and 6,13-dihydro-6,13-diborapentacenes have been prepared for the first time and studied. 2-Substituted-2,5-dihydro-1,2-oxaboroles were prepared by either a ring closing metathesis from (allyloxy)(N,N-diisopropylamino)vinylborane or a boron-tin exchange reaction of 2,2-dibutyl-2,5-dihydro-1,2-oxastannole with phenylboron dichloride. Treatment with base afforded the corresponding 1,2-oxaborolides. The 1H, 13C, 11B NMR spectral chemical shift values of 2-phenyl-1,2-oxaborolide are very similar to those of 1-methyl-2-phenyl-1,2-azaborolide which implies a similarity in their electronic structure. On treatment with [Cp*RuCl]4 or (CH3CN)3Mn(CO)3PF6, 2-phenyl-1,2-oxaborolide was converted to RuCp* or Mn(CO)3 complexes, respectively. Structural characterization of both complexes by single-crystal X-ray diffraction indicated that the metals are n5-bound to the ligand. 1,2-Dihydro-2-phenyl-1,2-oxaborine was obtained from the reaction of potassium 2-phenyl-1,2-oxaborolide with methylene chloride and base. The product was converted to its phenyl-Cr(CO)3 complex, which was structurally characterized. The intra-ring bond lengths of the heterocycle suggest that it has aromatic character. Pentacene and its derivatives are promising compounds for uses as organic electronic materials. Three derivatives of the related 6,13-dihydro-6,13-diborapentacenes have been prepared and structurally characterized. The dibromo- and dimethyl- derivatives show a π-π stacking in the solid state. In principle, this type of packing is more favorable for intermolecular electronic interaction than the herringbone stacking shown by pentacene.

The ability to improve performance of the high-end metal oxide semiconductor field effect transistor (MOSFET) is highly reliant on the dimensional scaling of such a device. In scaling, a decrease in dielectric thickness results in high leakage current between the electrode and the substrate by way of direct tunneling through the gate dielectric. Observation of a high leakage current when the standard gate dielectric, SiO2, is decreased below a thickness of 1.5 nm requires engineering of a replacement dielectric that is much more scalable. This high- dielectric allows for a physically thicker oxide, reducing leakage current. Integration of select lanthanide-based oxides and silicates, in particular lanthanum oxide and silicate, into MOS gate stack devices is examined. The quality of the high-K dielectrics is monitored electrically to determine properties such as equivalent oxide thickness, leakage current density and defect densities. In addition, analytical characterization of the dielectric and the gate stack is provided to examine the materialistic significance to the change of the electrical properties of the devices. It is shown that optimization of low-temperature processing can result in MOS devices with an equivalent oxide thickness (EOT) as low 5 Å and a leakage current density of 5.0 A⁄cm2. High-temperature processing, consistent with a MOSFET source-drain activation anneal, yields MOS devices with an EOT as low as 1.1 nm after optimization of the TaN/W electrode properties. The decrease in the device effective work function (phi_M,eff) observed in these samples is examined in detail. First, as a La2O3 capping layer on HfSiO(N), the shift yields ideal-phi_M,eff values for nMOSFET deices (4.0 eV) that were previously inaccessible. Other lanthanide oxides (Dy, Ho and Yb) used as capping layers show similar effects. It is also shown that tuning of phi_M,eff can be realized by controlling the extent of lanthanide-silicate formation. This research, conducted in conjunction with SEMATECH and the SRC, represents a significant technological advancement in realizing 45 and sub-45 nm MOSFET device nodes.

According to the International Technology Roadmap for Semiconductors (2004) integrating a high dielectric constant (high-k) material into the gate stack will be necessary within the next two years (i.e., by 2007) to maintain the rate of scaling that has come to characterize the microelectronics industry. This work presents results for Y-, Zr-, Hf-, and La-based high-k gate dielectrics prepared by ex-situ oxidation of sputtered thin metal films and for HfO2 prepared by atomic layer deposition (ALD). The kinetics of substrate consumption during formation of yttrium silicate thin films were studied. We find results consistent with high-k dielectric formation by a two-step process in which yttrium metal reacts with the silicon substrate to form a metal silicide which is then oxidized to form the yttrium silicate dielectric. In other experiments, we show flatband voltage shifts of -0.2 and 0.95V in devices containing Zr-based dielectrics formed by oxidation of 8Å of Zr metal on Si at 600°C in N2O for 15 and 300s, respectively. Silicon oxidized in the same environment does not show this shift. The fixed charge scales with EOT for these films and is consistent with charge generation due to disruption of the SiO2 network by metal ions. Zr-based dielectrics exhibit this effect more strongly than Hf-based dielectrics. We show that La-based dielectrics absorb atmospheric H2O and CO2, and that reactions between these materials and deposited silicon electrodes are accelerated when H2O or other OH species are present at the interface. We show that the electrical properties of gate stacks having Ru and RuO2 electrodes in contact with PVD Y-silicate are more stable during thermal anneal than similar gate stacks having PVD ZrO2 or CVD Al2O3 dielectrics. For this work, we configured a Fourier transform infrared spectrometer for in-situ attenuated total reflection measurements and investigated ALD deposition of HfO2. We report the direct reaction of tetrakis(diethylamino) hafnium (TDEAHf) with SiH groups on HF-last Si. Island growth of HfO2 occurs, and SiH features are still present and shrinking after 200 cycles. To the best of our knowledge, these are the first in-situ FTIR results presented for atomic layer deposition using TDEAHf/H2O chemistry.

Thiophene-based conjugated materials have received much attention as a novel class of organic semiconducting materials due to their excellent electronic and optical properties. To determine the influence of planarization on the properties of these conjugated molecules, a series of fused-ring poly- and oligothiophenes were designed and synthesized. Their properties, including electronic/electrochemical properties and solid-state packing, were studied and compared to the non-fused analogs. Two series of planarized oligomers were synthesized. Fused-ring oligothiophenes, in which one or more thiophene rings were replaced by thieno[3,2- b]thiophene and dithieno[3,2-b:2',3'-d]thiophene units, were prepared by a combination of cross coupling and oxidative coupling reactions. Fully fused oligothienoacenes were synthesized by Pd-catalyzed coupling of Bu3SnSSnBu3 with beta-Br-substituted oligomers to introduce sulfur linkages followed by oxidative ring closure. Removable solubilizing groups were introduced for oligomers with poor solubility to facilitate purification. The structural similarity of these oligomers offers the flexibility to systematically explore the ring fusion effect on the properties of oligothiophenes. It was found that oligomers with the same number of double bonds, but varying in the number and position of sulfur linkages, display a similar longest wavelength of absorption in solution. However, the introduction of sulfur linkages into these oligothiophenes leads to a blue shift of the longest wavelength emission and a correspondingly smaller Stokes shift. Although ring fusion has little effect on the solution absorption spectra, the solid-state spectra are dramatically different because the number and position of sulfur linkages alters the intermolecular interactions. X-ray diffraction data suggest that introduction of sulfur linkages favors pi-stacked packing motifs in contrast to the herringbone packing of non-fused oligothiophenes. Incorporation of fused-ring units into conjugated polymers was investigated by synthesizing and characterizing a series of alkyl-substituted polythieno[3,2-b]thiophenes. The mono-alkyl substituted polymer prepared via Stille coupling of a differentially functionalized monomer displayed a longer lambdamax of absorption and a corresponding lower optical band gap when compared to regiorandom polymers. Introducing a second alkyl chain into the monomer leads to decreased conjugation as observed in both electronic spectra and electrochemistry of a dialkyl-substituted polymer.

This dissertation describes the synthesis of phthalocyanines having specialized structures that provide for electrochemical studies of their fundamental properties and/or for direct preparation of phthalocyanine-based electronic materials. Much of the synthetic effort herein is directed toward the development of a particular class of phthalocyanine, herein referred to as benzimidazoporphyrazines. Benzimidazoporphyrazines are desirable substitutes for typical phthalocyanines in applications requiring phthalocyanine-based materials. The value of benzimidazoporphyrazines is derived from their geometry, which provides four substitution positions at peripheral carbon atoms that lie along the N-N axes of the macrocycles. The modular construction of pigment arrays that include phthalocyanines may be greatly facilitated with the use of benzimidazoporphyrazines. The history of research in benzimidazoporphyrazines is brief, and has not heretofore provided access to benzimidazoporphyrazines bearing substituents that may serve as synthetic handles for modification of the pigments after their formation. This report details the development of synthetic methodology to prepare benzimidazoporphyrazines that bear useful synthetic handles. The synthesis of a set of such pigments is also described. Additionally, the new pigments (and one pigment array) are studied with regard to structural confirmation, as well as by photochemical and electrochemical means.

The thermocouple systems used for the measurement of surface temperature in high temperature applications such as advanced aerospace propulsion systems and diesel engine systems are expected to perform in rapidly fluctuating and extremely high heat fluxes corresponding to high temperatures (in excess of 1400 K) and high speed flows. Traditionally, Pt/Pt-Rh based thin film thermocouples have been used for surface temperature measurements. However, recent studies indicated several problems associated with these thermocouples at temperatures exceeding 1000 K, some of which include poor adhesion to the substrate, rhodium oxidation and reaction with the substrate at high temperatures. Therefore, there is an impending demand for thermoelectric materials that can withstand severe environments in terms of temperature and heat fluxes. In this study, thin films of titanium carbide and tantalum carbide as well as two families of conducting perovskite oxides viz., cobaltites and manganates (La(1-x)SrxCoO3, M(1-x)Cax MnO3 where, M=La,Y) were investigated for high temperature thin film thermocouple applications as alternate candidate materials. Thin films of the carbides were deposited by r.f. sputtering while the oxide thin films were deposited using pulsed laser ablation. Sapphire (1102) was used as substrate for all the thin film depositions. All the thin films were characterized for high temperature stability in terms of phase, microstructure and chemical composition using x-ray diffraction, atomic force microscopy and electron spectroscopy for chemical analysis respectively. Electrical conductivity and seebeck coefficients were measured in-situ using a custom made device. It was observed that TiC/TaC thin film thermocouples were stable up to 1373 K in vacuum and yield high and fairly stable thermocouple output. The conducting oxides were tested in air and were found to be stable up to at least 1273 K. The manganates were stable up to 1373 K. It was observed that all the oxides studied crystallize in a single phase perovskite structure. This phase is stable up to annealing temperatures of 1373 K. The predominant electrical conduction mechanism was found to be small polaron hopping. Stable and fairly high electrical conductivities as well as seebeck coefficients accompanied with phase, structure, composition and microstructure stability indicate that these materials hold excellent promise for high temperature thin film thermocouple applications.