This dissertation includes two parts. In the first part the study is focused on the fabrication of multifunctional thin films for photovoltaic applications. There is no doubt about the importance of transforming world reliance from traditional energy resources, mainly fossil fuel, into renewable energies. Photovoltaic section still owns very small portion of the production, despite its fast growth and vast research investments. New methods and concepts are proposed in order to improve the efficiency of traditional solar cells or introduce new platforms. Recently, ferroelectric photovoltaics have gained interest among researchers. First objective in application of ferroelectric material is to utilize its large electric field as a replacement for or improvement of built-in electric field in semiconductor p-n junctions which is responsible for the separation of generated electron-hole pairs. Increase in built in electric field will increase open-circuit voltage of the solar cell. In this regard, thin films of ferroelectric hafnium dioxide doped with silicon have been fabricated using physical vapor deposition techniques. Scanning probe microscopy techniques (PFM and KPFM) have been employed to analyze ferroelectric response and surface potential of the sample. The effects of poling direction of the ferroelectric film on the surface potential and current-voltage characteristics of the cell have been investigated. The results showed that the direction of poling affects photoresponse of the cell and based on the direction it can either improved or diminished. In the second part of this work, epitaxial thin films have been synthesized with physical vapor deposition techniques such as sputtering and electron beam evaporation for the ultimate goal of producing multifunctional three-dimensional structures. Three-dimensional structures have been used for applications such as magnetic sensors, filters, micro-robots and can be used for modification of the surface of solar cells in order to improve light absorption and efficiency. One of the important techniques for producing 3-D structures is using origami techniques. The effectiveness of this technique depends on the control of parameters which define direction of bending and rolling of the film or curvature of the structure based on the residual stress in the structure after film’s release and on the quality and uniformity of the film. In epitaxially grown films, the magnitude and direction of the stress are optimized, so the control over direction of rolling or bending of the film can be controlled more accurately. For this purpose, deposition conditions for epitaxy of Zn, Fe, Ru, Ti, NaCl and Cr on Si, Al2O3 or MgO substrates have been investigated and optimized. Crystallinity, composition and morphology of the films were characterized using reflective high energy diffraction (RHEED), Auger electron spectroscopy (AES), energy dispersive X-ray (EDX), and scanning electron microscopy (SEM).

O presente trabalho realiza a investigação dos parâmetros hiperfinos, incluindo a sua natureza dinâmica, em compostos ligantes em solução a temperatura ambiente (295 K) e resfriada (77K) através da espectroscopia de Correlação Angular γγ Perturbada (CAP). Para a realização das medidas experimentais, utilizou-se núcleos de prova radioativos de 111In111Cd, 181Hf181Ta e 111mCd111Cd, que decaem através de cascata gama. As amostras foram preparadas diluindo-se soluções com os núcleos radioativos em água, quando se investigou a interação do núcleo de prova com o ligante água; adicionando-se soluções com os núcleos radioativos em solução tampão, quando se investigou a interação do núcleo de prova com os íons ligantes provenientes do próprio tampão (CO32- e HCO31-) e com o OH1-; e adicionando-se soluções com os núcleos radioativos em soluções do ligante ácido etilenodiaminotetracético (EDTA), este em pH entre 4,0 e 5,0, (que corresponde ao pH da própria solução saturada do EDTA) e em solução tampão de pH entre 9 e 10. Assim foi possível investigar os efeitos gerados por cada um desses métodos de preparação de amostras nas medidas CAP. Finalmente foi feita uma análise comparativa para os vários métodos de inserção dos núcleos de prova na amostra, considerando-se aspectos químicos e nucleares. A inexistência de medidas para esse tipo de amostra, justifica a importância dos resultados obtidos. / In this study the hyperfine parameters, including the dynamical nature, Perturbed Angular Correlation (PAC) spectroscopy was used to measure the hyperfine parameters in molecules of ligand compounds in solutions. The measurements were carried out at 295 K and 77 K using 111In111Cd, 181Hf181Ta and 111mCd111Cd, as probe nuclei. Samples were prepared by adding a small volume of radioactive solution containing the probe nuclei in aqueous solution, buffer solution and ethylenediaminetetraacetic acid (EDTA) used as a ligand with pH 4.3 which correspond to the pH of the saturated EDTA solution and in buffer solution with pH between 9 and 10. The results made possible to understand the impact of each method for PAC measurements. Finally a comparative analysis for the several methods of inserting of the probe nuclei in the sample was made, considering chemical and nuclear aspects. The lack of measurements in this kind of samples justifies the importance of the obtained results.

O presente trabalho realiza a investigação dos parâmetros hiperfinos, incluindo a sua natureza dinâmica, em compostos ligantes em solução a temperatura ambiente (295 K) e resfriada (77K) através da espectroscopia de Correlação Angular γγ Perturbada (CAP). Para a realização das medidas experimentais, utilizou-se núcleos de prova radioativos de 111In111Cd, 181Hf181Ta e 111mCd111Cd, que decaem através de cascata gama. As amostras foram preparadas diluindo-se soluções com os núcleos radioativos em água, quando se investigou a interação do núcleo de prova com o ligante água; adicionando-se soluções com os núcleos radioativos em solução tampão, quando se investigou a interação do núcleo de prova com os íons ligantes provenientes do próprio tampão (CO32- e HCO31-) e com o OH1-; e adicionando-se soluções com os núcleos radioativos em soluções do ligante ácido etilenodiaminotetracético (EDTA), este em pH entre 4,0 e 5,0, (que corresponde ao pH da própria solução saturada do EDTA) e em solução tampão de pH entre 9 e 10. Assim foi possível investigar os efeitos gerados por cada um desses métodos de preparação de amostras nas medidas CAP. Finalmente foi feita uma análise comparativa para os vários métodos de inserção dos núcleos de prova na amostra, considerando-se aspectos químicos e nucleares. A inexistência de medidas para esse tipo de amostra, justifica a importância dos resultados obtidos. / In this study the hyperfine parameters, including the dynamical nature, Perturbed Angular Correlation (PAC) spectroscopy was used to measure the hyperfine parameters in molecules of ligand compounds in solutions. The measurements were carried out at 295 K and 77 K using 111In111Cd, 181Hf181Ta and 111mCd111Cd, as probe nuclei. Samples were prepared by adding a small volume of radioactive solution containing the probe nuclei in aqueous solution, buffer solution and ethylenediaminetetraacetic acid (EDTA) used as a ligand with pH 4.3 which correspond to the pH of the saturated EDTA solution and in buffer solution with pH between 9 and 10. The results made possible to understand the impact of each method for PAC measurements. Finally a comparative analysis for the several methods of inserting of the probe nuclei in the sample was made, considering chemical and nuclear aspects. The lack of measurements in this kind of samples justifies the importance of the obtained results.

Current plastics are mostly derived from petrochemical sources, as it is a finite resource renewable replacements are sought after. Polymers derived from cyclic esters such as; lactide, valerolactone and caprolactone are of interest. An industrially viable method of producing stereocontrolled polylactide (PLA) from rac-lactide is desired. Previous work on poly(cyclic esters) is overviewed in chapter 1 with an emphasis upon PLA. Chapter 2 reports the coordination of Ti(OiPr)4 to homo/piperazine bridged bis(phenol) (salan) ligands. Under ambient conditions bimetallic structures were produced and a steric dependent equilibrium system is discussed. Forcing conditions resulted in monometallic homopiperazine salan complexes. Their application for the ring-opening-polymerisation (ROP) of rac-lactide is investigated. Homo/piperazine salan titanium catecholates were synthesised and their cytotoxicity investigated by collaborators. Chapter 3 details the synthesis of monometallic homopiperazine salan zirconium/hafnium isopropoxide complexes. Their utility for the ROP of rac-lactide in solution and solvent free systems are discussed. Bimetallic or tetrametallic solid state structures from attempts to coordinate Zr(IV)/Hf(IV) metals to piperazine salan ligands are also discussed. Chapter 4 discusses the complexation of AlMe3 with homopiperazine salan ligands. The resulting monometallic complexes were inactive for the ROP of lactide. Benzyl alcohol derivatives were synthesised and trialled for solvent free ROP of rac-lactide, δ-valerolactone, ε-caprolactone. Co-polymerisations were investigated and a tri-block polymer of poly(ε-caprolactone/δ-valerolactone/rac-lactide) was prepared. Chapter 5, trans-1,4-DACH salen ligands were synthesised and investigated as ligands with Al(III), Ti(IV), Zr(IV), and Zn(II) metal centres. Bimetallic Al(III) and Ti(IV) structures were characterised and trialled for the ROP of rac-lactide. Isotactic PLA was reported for aluminium complexes, dependent upon phenoxy substituents, and these polymerisations were shown to be immortal in nature. Chapter 6 details the synthesis of trans-1,2-DACH salalen ligands which were complexed to AlMe3, these initiators were investigated for the solution ROP of rac-lactide. The further synthesis of benzyloxy derivatives is also reported and they were utilised for solution and solvent free polymerisations of rac-lactide. The initiator’s behaviour is discussed with respect to varying amine and imine groups.

We have investigated the structure and interfacial structure of two types of high-k dielectric thin films on Si using combined experimental and theoretical approaches. In the Hf-based high- k dielectrics, the crystallinity of three films, pure HfO2, Y-incorporated HfO2 and Al-incorporated HfO2, is examined by transmission electron diffraction (TED), and the local coordination symmetries of the Hf atoms in the films are revealed by the profile of electron energy-loss near-edge structure (ELNES) taken at oxygen K-edge. These ELNES spectra are then simulated using real-space multiple-scattering (RSMS) method. We find a good agreement between the experimental and the simulated result of pure HfO2. The incorporation of Y indeed stabilizes HfO 2 to a cubic structure, but it also contributes to possible lattice distortion and creation of complex defect states, causing discrepancies between the experimental and the simulated result. As a comparison, the local coordination symmetry of Hf is largely degraded upon the incorporation of Al, which not only amorphorizes HfO2, but also introduces significantly amount of O vacancies in the film. We have further investigated the interfacial structures of HfO2 and Al-incorporated HfO2 thin films on Si using spatially resolved ELNES, which a series of the oxygen K-edge spectra is acquired when a 0.3 nm electron probe scanning across the film/Si interface. We find that interfaces are not atomically sharp, and variation in the local coordination symmetry of Hf atoms lasts for a couple of monolayers for both the HfO2 and the Al-incorporated HfO2 samples. Annealing of the HfO2 film in the oxygen environment leads to the formation of a thick SiO2/SiOx stack layer in-between the original HfO2 and the Si substrate. As a comparison, the interfacial stability is significantly improved by incorporating Al into the HfO 2 film to form HfAlO, which effectively reduces/eliminates the interfacial silicon oxide formation during the oxygen annealing process. The interfacial structure of SiTiO3 (STO) dielectric and Si is significant different from that between Hf-based dielectric and Si, as the crystalline STO is epitaxially grown on the Si. Together with the high resolution high-angle annular-dark-field (HAADF) image, the spatially resolved ELNES acquired across the STO/Si interface reveal an amorphous interfacial region of 1-2 monolayer thickness, which is lack of Sr, but contains Ti, Si, and O. Based on these experimental evidences, we propose a classical molecular dynamic (MD) interface model, in which the STO is connected to Si by a distorted Ti-O layer and a complex Si-O layer. The simulated results, based on the MD interface model, generally agree with the experimental results, disclosing a gradual change of the local atomic coordination symmetry and possible defect incorporation at the interface. / Wang, Xiaofeng = Si衬底上高k介电薄膜的结构研究 / 王晓峰. / Adviser: Li Quan. / Source: Dissertation Abstracts International, Volume: 72-11, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 103-112). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Wang, Xiaofeng = Si chen di shang gao k jie dian bo mo de jie gou yan jiu / Wang Xiaofeng.

The scaling of integrated circuits requires the use of alternative dielectric materials as the replacement for silicon dioxide in the submicron devices. The scaling limit for silicon dioxide used in MOSFETs is 1.2nm and the Oxide Nitride Oxide (ONO) stack used in flash memory applications is 13.0nm. The use of alternative dielectrics with high- κ value will alleviate the problem of charge retention and also would help to decrease the programming voltage in case of flash memory cells. Many alternative high- κ dielectric materials such as TaO2, TiO2, Al2O3 etc., have been examined for this purpose previously. Recently the metal oxides such as ZrO2 and HfO2 have been found to be viable replacements for the existing oxide. The high- κ value along with high bandgap motivates this replacement. A complete modeling of the reactively sputtered HfO2 films in the thickness range of 294Å to 480Å is attempted using the data obtained by one of the group members at the Sharp Laboratories of America, Inc. The IV and CV data is used to characterize the material properties and conduction mechanism in HfO2 films used as a control dielectric. The slope of the Poole-Frenkel plot is close to the theoretical value in the intermediate region however it starts to deviate at high field regions. Temperature dependent data also suggests that there are two types of vii traps active in the intermediate and high field regions. However the origin of these traps is not known. Temperature dependent data indicates that there is a rapid increase in the leakage current at elevated temperatures in the high field region further suggesting that the charge retention capability of the device would be adversely affected under such conditions.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Tridentate "pincer" ligands provide a unique balance of stability and reactivity in organometallic chemistry. The development of diarylamido-based PNP pincer ligands has led to many applications in catalysis, including the potential to facilitate unique chemical transformations at transition metal centers. The main objective of this thesis was to explore transition metal chemistry supported by the PNP pincer framework for both early and late transition metals. In Chapter I, the history behind the design and synthesis of pincer complexes is described. The advantages and disadvantages of various pincer ligands are reviewed to show the reasoning behind the synthesis of the PNP pincer framework. Chapter II discusses the synthesis of novel Hf and Ta complexes involving the PNP ligand. Reactions of (PNP)HfCl3 with large alkyl Grignards led to double alkylation and triple alkylation was achieved with methyl Grignard. (PNP)HfMe3 and (PNP)Hf(CH2SiMe3)2Cl displayed remarkably irregular coordination environments about hafnium, in contrast to the approximately octahedral structure of (PNP)HfCl3. (PNP)HfMe3 was found to be thermally stable at 75 degrees C, whereas thermolysis of (PNP)Hf(CH2SiMe3)2Cl under similar conditions led to a mixture of products. The major decomposition product is believed to be a Hf alkylidene complex on the basis of in situ NMR spectroscopic observations (e.g., delta 248.2 ppm in the 13C{1H} NMR spectrum). The reaction of (PNP)TaF4 with an excess of ethyl Grignard led primarily to the double alkylation product, (PNP)Ta(CH2CH3)2F2. Repeating this reaction in the presence of excess ethyl Grignard and dioxane resulted in the formation of an ethylene complex, (PNP)Ta(=CHCH3)(C2H4). In Chapter III, a C-C reductive elimination study is described comparing two pincer ligand scaffolds: Me(PNP) ligand and TH(PNP) ligand. The tied ligand has previously been found to be more sterically demanding than the untied ligand, which has allowed for faster N-C cleavage, faster oxidative addition and a more selective alkyne dimerization catalyst. This study reveals that the tied ligand complex, TH(PNP)Rh(C6H4CF3)(Ph), undergoes slower reductive elimination of p-Ph-C6H4CF3 (< 4% after 7 h at 38 degrees C; t1/2 = 7.7 h at 64 degrees C; t1/2 = 2.13 h at 75 degrees C) than Me(PNP)Rh(C6H4CF3)(Ph) (t1/2 = 15.6 min at 38 degrees C).

HfO2 is a popular replacement for SiO2 in modern CMOS technology. It is used as the gate dielectric layer isolating the transistor channel from the gate. For this application, certain material property demands need to be met, most importantly, a high static dielectric constant is desirable as this positively influences the effectiveness and reliability of the device. Previous theoretical calculations have found that this property varies with the crystal structure of HfO2; specifically, the tetragonal structure possesses the highest dielectric constant (~70 from theoretical calculations) out of all possible stable structures at atmospheric pressure, with the cubic phase a far second (~29, also calculated). Following the results from previous experimental work on the phase formation of sputtered HfO2, this study investigates the possibility of producing thin films of HfO2 with the cubic or tetragonal structure by the addition of nitrogen to a reactive sputtering process at various deposition temperatures. Also, a new physical vapor deposition method known as High Power Impulse Magnetron Sputtering (HiPIMS) is employed for its reported deposition stability in the transition zone of metal-oxide compounds and increased deposition rate. Structural characterization of the produced films shows that films deposited at room temperature with a low N content (~6 at%) are mainly composed of amorphous HfO2 with mixed crystallization into t-HfO2 and c-HfO2, while pure HfO2 is found to be composed of amorphous HfO2 with signs of crystallization into m-HfO2. At 400o C deposition temperature, the crystalline quality is enhanced and the structure of N incorporated HfO2 is found to be c-HfO2 only, due to further ordering of atoms in the crystal lattice. Optical and dielectric characterization revealed films with low N incorporation (&lt; 6 at%) to be insulating while these became conductive for higher N contents. For the insulating films, a trend of increasing static dielectric constant with increasing N incorporation is found.

A series of tetravalent zirconium and hafnium complexes were developed in their abundant chemistry and photophysical properties, where those complexes were supported by diarylamido-phosphino [iPr-PNP]- (bis(o-diisopropylphosphinophenyl)amide) ligand. [iPr-PNP]MCl3 (M = Zr, Hf) were prepared by sequentially reacting [iPr-PNP]H with n-butyllithium and following MCl4(THF)2 in toluene solution under ambient temperature. UV-Vis absorption, emission, excitation spectrum, cyclic voltammetry experiments, and density functionalization theory (DFT) calculations are applied to approach their unique photophysical phosphorescence properties. Alkyls which are lack of £]-hydrogen have been used to achieve in synthesis of degenerate ([iPr-PNP]MR3, R = Me, CH2SiMe3) or non-degenerate ([iPr-PNP]M(E)(R)2, R = CH2SiMe3, E = Cl, Me) derivatives since we could control the desired product from steric effect. Strong fluxional exchange was found in those complexes. By variable temperature NMR monitoring and X-ray diffraction, their fluxionality seems interesting not only in mechanism, but it does affect our reaction. By heating [iPr-PNP]Zr(Cl)(CH2SiMe3)2 in solution, we can afford new alkylidene complexes [iPr-PNP]M(Cl)(=CHSiMe3) via self £\-abstraction. Through variable temperature analysis, the activation energy of £\-abstraction have £GH‡ = 18.5 kcal/mol and £GS‡ = -19.8 cal/mol¡PK. Here we also can identified multiple alkylidene derivatives of [iPr-PNP]Zr(Me)(=CHSiMe3)2. The computational studies of [MeNPiPr]Ni(R)(L) ([MeNPiPr]- = o-diisopropylphosphinoII phenyl-2,6-dimethylanilite, R = Me, CH2SiMe3; L = 2,4-Lutidine, Py, PMe3) in C-H activation has been fully established. Start on dissociation mechanism, we considered three major pathways to explain the activation mechanisms including isomerisation, direct intermolecular benzene activation, and intramolecular sp3 C-H acitvaition. Here we also account H-D exchange as experimental observation. Important intermediates and transition states are found to locate the energy maps to assist our experiments.