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xv, 101 p. ; ill. (some col.) A print copy of this title is available through the UO Libraries under the call number: KNIGHT QC176.84.E5 P47 2007 / Silver films with nanoscale to mesoscale thicknesses were produced by chemical reduction onto silica substrates and their physical and electrical properties were investigated and characterized. The method of silver deposition was developed in the context of this research and uses a single step reaction to produce consistent silver films on both flat silica coverslips and silica nanospheres of 250-1000 nm. Both the structure and the electrical properties of the silver films are found to differ significantly from those produced by vacuum deposition. Chemically deposited (CD) silver is not uniformly smooth, but rather is granular and porous with a network-like structure. By quantitatively accounting for the differences in scale, geometry, and microstructure of the CD films, it is found that the same models used to describe the resistivity of vacuum deposited films may be applied to CD films. A critical point in the analysis that allows this relation involves the definition of a geometric parameter, g, which replaces the thickness, t, as the critical length that influences the electrical properties of the film. The temperature dependent properties of electrical transport were also investigated and related to the microstructure of the CD films. A detailed characterization of CD silver as shells on silica spheres is also presented including physical and optical properties. In spite of the rough and porous morphology of the shells, the plasmon resonance of the core-shell structure is determined by the overall spherical shell structure and is tunable through variations in the shell thickness. Preliminary investigations into the electrical transport properties of aggregates of silver coated spheres suggest similarities in the influence scale, geometry, and microstructure to silver films on flat substrates. The aggregates of shells also exhibit pressure related resistance behavior due to the composite structure. / Adviser: Miriam Deutsch

Ph.D. / In the search to improve the conversion efficiency of solar cells such as α-Si and CuInSe2 cells, attention have recently been focused on the use of transparent conducting oxides (TCO's) as window layers and top electrodes in these cells. Materials such as indium tin oxide (ITO) and fluorine-doped tin oxide (FTO) thin films were used due to their excellent electro-optical properties, but it was found that they were unstable when subjected to a hydrogen plasma (during the a-Si deposition) and that the materials reduced to their metallic forms, degrading their electrical and optical properties. Zinc oxide (ZnO), however, possess electrical and optical properties equal to ITO and FTO, but is stable in the presence of a hydrogen plasma. In this study a system for the deposition of ZnO thin films by spray pyrolysis was developed and the films successfully deposited. The films were also doped with A1C1 3 in an attempt to further improve the films' conductivities. The films were then characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), electrical measurements (Hall and four-point probe measurements) and optical analyses of the films. The films were compared with films deposited by atomic layer epitaxy (ALE) and DC sputtering. It was found that the films were crystalline with a predominantly (002) preferred orientation. The addition of Al as dopant, however, resulted in the film structure deteriorating. The SEM micrographs obtained of the films indicated films with a close-packed structure, existing of small grains and the film surface having a textured appearance. It was further found that the deposition parameters of the films influenced both the structures of the films and the morphologies and the micrographs indicated that the addition of Al as dopant resulted in the film formation being inhibited and even resulting in no proper film being deposited. It was found that the as-deposited ZnO films were resistive and that the films had to be subjected to a post-deposition annealing to decrease the film resistivity. The annealing conditions were investigated and it was found that annealing the films in hydrogen at their deposition temperature for an hour resulted in the largest decrease in the films' resistivities, typically two orders of magnitude. Studies of the substrate temperature indicated that the films had to be deposited at between 350 and 420°C and that a reduction in the substrate temperature resulted in the film resistivity increasing. Contrary to literature, it was found that the addition of Al as dopant had no beneficial influence on the electrical properties of the films and that dopant concentrations exceeding 1.0 at.% resulted in the film resistivity increasing. The films were characterized optically by analysing the transmission spectra obtained of the films, using the envelope technique. It was found that the films had transmissions exceeding 95% and that the refractive indices and optical gaps centred around 1.99 and 3.3 eV respectively. Both properties were affected by the deposition parameters. The ZnO films deposited by spray pyrolysis compared excellently with the films prepared by ALE and DC sputtering in all aspects. It is hence clear that ZnO films, with characteristics suitable for solar cell application, can be deposited by the simple and inexpensive technique of spray pyrolysis.

Orientador: Varlei Rodrigues / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-31T16:45:14Z (GMT). No. of bitstreams: 1 Ferreira_RafaelCintraHensel_M.pdf: 43759995 bytes, checksum: 8636f117e63053d6b540d65b95c34072 (MD5) Previous issue date: 2016 / Resumo: Os filmes orgânicos ultrafinos tem permitido funcionalizar superfícies a fim de introduzir propriedades específicas que diferem daquelas apresentadas em escala macroscópica. Um processo versátil para modificar superfícies e criar sistemas multifuncionais é a técnica de automontagem por adsorção física (LbL, do inglês Layer-by-Layer), na qual nanoestruturas são formadas devido a adsorção de moléculas com cargas opostas em arquiteturas moleculares multicamadas. O monitoramento elétrico do crescimento dos filmes é essencial em experimentos nos quais não são permitidas caracterizações ópticas. Além disto, é importante compreender as propriedades elétricas destes filmes devido a sua utilização em sensores capacitivos para análise química. Deste modo, neste trabalho desenvolvemos um equipamento capaz de acompanhar o crescimento de filmes LbL por meio de medidas de capacitância após a deposição de cada camada de polieletrólitos sobre eletrodos interdigitados (IDEs, do inglês Interdigitated Electrodes). Observamos um aumento linear da capacitância devido ao acúmulo de material dielétrico sobre os IDEs, com uma alternância na medida de capacitância de acordo com o polieletrólito depositado, isto é, há uma reversão de carga na camada mais externa quando a adsorção do policátion é compensada pela do poliânion, ou vice-versa. Utilizando o modelo para o potencial eletrostático de um IDE proposto por M. W. Den Otter, desenvolvemos uma nova metodologia para investigar a constante dielétrica da estrutura multicamadas formada. Obtivemos (16 ± 1) para a constante dielétrica do filme LbL (PDDA/CuTsPc), e (21 ± 3) para a arquitetura (PDDA/PSS), ambos em satisfatória concordância com a literatura. Ademais, desenvolvemos um modelo para interpretar o deslocamento na capacitância medida após a adsorção do policátion a fim de determinar sua densidade de carga superficial, que diminuiu de (0,23 ± 0,02) e/µm2 para (0,08 ± 0,01) e/µm2 quando o PDDA (policátion fortemente carregado) foi substituído pelo PAH (policátion fracamente carregado) para ambos os poliânions analisados. Portanto, desenvolvemos um equipamento para monitorar o crescimento de filmes LbL e uma metodologia que permite obter informações sobre o comportamento dielétrico dos filmes a cada camada depositada, o que pode auxiliar na escolha dos materiais e espessura dos filmes LbL utilizados como elementos transdutores em desenvolvimentos futuros / Abstract: Organic ultrathin films have enabled surface¿s functionalization in order to introduce specific properties which differ from those in macroscopic scale. A versatile process to modify surfaces and create multifunctional systems is the layer-by-layer (LbL) technique, in which the nanostructures are formed due to the adsorption of charged molecules in multilayered molecular architectures. The electrical monitoring of the film's growth is essential in experiments in which optical characterizations can not be used. Moreover, it is important to comprehend the electrical properties of these films owing to their application on capacitive sensors for chemical analysis. In this research we developed a home-made setup to keep track of the LbL film¿s growth by measuring the capacitance after each deposited layer onto interdigitated electrodes (IDEs). We have observed a linear increase in the capacitance due to accumulated dielectric material onto the IDEs, along with an alternation in the measured capacitance according to the deposited polyelectrolyte, i.e., a charge reversal of the outermost layer as the polycation adsorption is compensated by the polyanion adsorption, or vice-versa. Using the IDEs electrostatic potential model proposed by M. W. Den Otter, we have developed a new methodology to investigate the dielectric constant of the formed multilayered structure. A dielectric constant of (16 ± 1) was obtained for (PDDA/CuTsPc) films and (21 ± 3) for (PDDA/PSS) architecture, both in satisfactory agreement with the literature. Furthermore, we have developed a model to interpret the capacitance measurement shift after the polycation adsoption in order to investigate its surface charge density, which decreased from (0.23 ± 0.02) e/µm2 to (0.08 ± 0.01) e/µm2 when PDDA (strong polycation) was replaced by PAH (weak polycation) for both analyzed polyanions. Therefore, we have developed an equipment to monitor the LbL film's growth as well as a methodology that enables the obtaining of information about the film dielectric behavior at each deposited layer, which can assist in the choice of the materials and thickness of the LbL films that are used as transductor elements in future developments / Mestrado / Física / Mestre em Física / 147530/2014 / CNPQ

by Tsai Yau Moon = 錳氧化物的金屬-絶緣體轉變 : 多層薄膜及異構結 / 蔡友滿. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / by Tsai Yau Moon = Meng yang hua wu de jin shu-jue yuan ti zhuan bian : duo ceng bo mo ji yi gou jie / Cai Youman. / Abstract / 論文摘要 / Acknowledgements / Table of Contents / List of Figures / List of Tables / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Perovskite-type structure / Chapter 1.2 --- Metal-insulator transition / Chapter 1.3 --- Magnetoresistance / Chapter 1.3.1 --- Giant magnetoresistance (GMR) / Chapter 1.3.2.1 --- Colossal magnetoresistance (CMR) in perovskite manganites / Chapter 1.3.2.2 --- Possible origin of CMR / Chapter 1.4 --- Brief review of p-n junction between perovskite manganites and STON (001) / Chapter 1.5 --- Our project / Chapter 1.6 --- Scope of this thesis work / References / Chapter Chapter 2 --- Preparation and characterization of manganite thin films / Chapter 2.1 --- Thin film deposition / Chapter 2.1.1 --- Facing-target sputtering (FTS) / Chapter 2.1.2 --- Vacuum system / Chapter 2.1.3 --- Deposition procedure / Chapter 2.1.4 --- Deposition conditions / Chapter 2.1.5 --- Oxygen annealing system / Chapter 2.1.6 --- Silver electrode coating system / Chapter 2.2 --- Characterization / Chapter 2.2.1 --- Alpha step profilometer / Chapter 2.2.2 --- X-ray diffraction (XRD) / Chapter 2.2.3 --- Transport property measurement / References / Chapter Chapter 3 --- [LCSMO/PCMO] multilayers / Chapter 3.1 --- [LCSMO (100 A)/PCMO (X A)] multilayers / Chapter 3.1.1 --- Sample preparation / Chapter 3.1.2 --- Results and discussion / Chapter 3.1.2.1 --- Structural analysis / Chapter 3.1.2.2 --- Transport properties / Chapter 3.2 --- [LCSMO (50 A)/PCMO (X A)] multilayers / Chapter 3.2.1 --- Sample preparation / Chapter 3.2.2 --- Results and discussion / Chapter 3.2.2.1 --- Structural analysis / Chapter 3.2.2.2 --- Transport properties / References / Chapter Chapter 4 --- [LSMO/PCMO] multilayers and LSMO/STON p-n junction / Chapter 4.1 --- [LSMO/PCMO] multilayers / Chapter 4.1.1 --- Sample preparation / Chapter 4.1.2 --- Results and discussion / Chapter 4.1.2.1 --- Structural analysis / Chapter 4.1.2.2 --- Magnetization / Chapter 4.2 --- LSMO/STON heterojunction / Chapter 4.2.1 --- Sample preparation / Chapter 4.2.2 --- Results and discussion / Chapter 4.2.2.1 --- Structural analysis / Chapter 4.2.2.2 --- Metal insulator transition of LSMO revealed by four point I-V measurement / Chapter 4.3 --- Conclusion / References / Chapter 5 Conclusion / Chapter 5.1 --- Conclusion / Chapter 5.2 --- Future outlook

The 2006 International Technology Roadmap for Semiconductors projects that for 2020, interconnects will be as narrow as 14 nm and will operate at frequencies as high as 50GHz. For a wire that operates at ultra-high frequencies, such that skin depth and the mean free path of the electrons are in the same order, skin effect and surface scattering should be considered simultaneously. This is known as the anomalous skin effect (ASE). The objective of this work is to identify the challenges and opportunities for using GSI interconnects in the nanometer and GHz regime. The increase in the resistivity of a thin wire caused by the ASE is studied. The delay of a digital transmission line resulting from this effect is modeled. Compact models are presented for the bit-rate limit of transmission lines using a general form of resistance that for the first time simultaneously considers dc resistance, skin effect, and surface scattering. A conventional low-loss approximation that is only valid for fast rising signals is also relaxed. The impact of size effects on the design of multi-level interconnect networks is studied. For high-performance chips at the 18 nm technology node, it is shown that despite a more than four times increase in the resistivity of copper for minimum-size interconnects, the increase in the number of metal levels is negligible (less than 7%), and interconnects that will be affected most are so short that their impact on chip performance is inconsequential. It is shown that for low-cost applications where very few wiring pitches are normally used, the number of metal levels needed to compensate for the impact of size effects on the average rc delay of a copper interconnect is drastically high. An optimization methodology has been presented for power distribution interconnects at the local level. For a given IR drop budget, compact models are presented for the optimal widths of power and ground lines in the first two metal levels for which the total metal area used for power distribution is minimized.

The development of new materials and processes for electronic devices has been driven by the integrated circuit (IC) industry since the dawn of the computer era. After several decades of '"Moore's Law"-type innovation, future miniaturization may be slowed down by materials and processing limitations. By way of comparison, the nascent field of flexible electronics is not driven by the smallest possible circuit dimension, but instead by cost and form-factor where features typical of 1970s CMOS (i.e., channel length - IO μm) will enable flexible electronic technologies such as RFID, e-paper, photovoltaics and health monitoring devices. In this thesis. cyclohexasilane is proposed and used as a key reagent in solution processing of poly-Si and Co-Si thin films with the former used as the active layer in thin film transistors (TFTs) and the latter as the gate metal in metal-oxide-semiconductor (MOS) capacitors. A work function of 4.356 eV was determined for the Co-Si thin films via capacitance-voltage (C-Y) characterization which differs slightly from that extracted from ultraviolet photoemission spectroscopy (UPS) data (i.e., 4.8 eV). Simulation showed the difference between the C-V and UPS-derived data may be attributed to the existence of 8.3 x 10 (exponent 10) cm-2 interface charge density in the oxide-semiconductor junction. Poly-Si TFTs prepared using Si6 H12-based inks maintained the following electrical attributes: field effect mobility of 0.1 cm2V-1s-1; threshold voltage of 66 V; and, an on/off ratio of 1630. A BSIM3 version 3 NFET model was modified through global parametric extraction procedure to match the transfer characteristics of the fabricated poly-Si TFT. It is anticipated that this model can be utilized for future design simulation for solution-processed poly-Si circuits.

Indiana University-Purdue University Indianapolis (IUPUI) / Preparation and characterization of multiferroic materials in which ferroelectricity and ferromagnetism coexist would be a milestone for functionalized materials and devices. First, electric properties of polyvinylidene (PVDF) films fabricated using the Langmuir-Schaefer method have been studied. Films of different thickness were deposited on silicon substrates and analyzed using several techniques. X-ray diffraction (XRD) data showed that PVDF films crystallize at an annealing temperature above 130 °C. Polarization versus electric field (PE) ferroelectric measurements were done for samples prepared with electrodes. PE measurements show that the coercivity of the films increases as the maximum applied electric field increases. The coercivity dependence on the frequency of the applied electric field can be fitted as . The results also show that the coercivity decreases with increasing the thickness of PVDF film due to the pinning effect. Next, we have demonstrated that those PVDF properties can be controlled by applying an external magnetic field. Samples were created in a layered heterostructure, starting with a Fe thin film, PVDF above that, and followed by another thin film of Fe. Extended X-ray absorption fine structure (EXAFS) spectroscopy was used to study the interface between PVDF polymer films and ferromagnetic iron thin films. Conventional EXAFS was applied to identify the structure of a Fe film sandwiched between two PVDF layers. An electric signal was then applied to the polymer to study the effects polarizing the polymer has on the Fe atoms at the interface. This shows that the Fe atoms diffuse into the PVDF layer at the interface between the two layers. Polarizing the film causes further diffusion of Fe atoms into the polymer. We also found that as the applied magnetic field is changed, the switching of electric polarization for the PVDF displayed a dependence on the external magnetic field. We also noticed that both the coercivity and polarization for the PVDF polymer display hysteretic features as the applied magnetic field is changed. We also found that the thickness of both the iron layers and the PVDF layer has an effect on the magnetoelectric coupling in our samples. The same strain applied to a thicker PVDF layer becomes tougher to flip the polarization compared to a thinner PVDF layer. As the iron film thickness increases, the strain also increases, and the polarization of the PVDF polymer is more easily flipped. We also found that the magnetoelectric sensitivity increases as both the PVDF and iron layers increase in thickness. We have shown that it is possible to control the ferroelectric properties of a PVDF film by tuning the magnetic field in a heterostructure. Our experiments show a coupling between the electric polarization and applied magnetic field in multiferroic heterostructures much larger than any previously reported values. Previous reports have used inorganic materials for the ferroelectric layer. Organic polymers have an electric dipole originating at the molecular level due to atoms with different electronegativity that are free to rotate. To flip the polarization, the chains must rotate and the position of the atoms must change. This increases the force felt locally by those chains. Using this polymer, we are able to increase the magnetoelectric coupling.