<p>Abundant experimental analyses and theoretical computational analyses that had been performed on metals to understand anisotropy and its evolution and its dependence on initial orientation of grains have failed to provide theories that can be used in macro-scale plasticity. Ductile metals fracture after going through a large amount of plastic deformation, during which the anisotropy of the material changes significantly. Processed metal sheets or slabs possess anisotropy due to textures produced by metal forming processes (such as drawing, bending and press braking). Metals that were initially isotropic possess anisotropy after undergoing forming processes, <i>i.e</i>., through texture formation due to large amount of plastic deformation before fracture. It is therefore essential to consider the effect of anisotropy to predict the characteristics of fracture and plastic flow performances in the simulation of ductile fracture and plastic flow of materials. Crystal plasticity simulations carried out on grains at the meso-scale level with different initial orientations (ensembles) help to derive the evolution of anisotropy at the macro-scale level and its dependence on initial orientation of grains. This paper investigates the evolution of anisotropy in BCC and FCC metals and its dependence on grain orientation using crystal plasticity simulations and texture analysis to reveal the mechanics behind the evolution of anisotropy. A comparison of anisotropy evolution between BCC and FCC metals is made through the simulation, which can be used to propose the theory of anisotropy evolution in macro-scale plasticity. </p><p> <i>Keywords</i>: ensembles; grains; initial orientation; anisotropy; evolution of anisotropy; crystal plasticity; textures; homogeneity; isotropy; inelastic; equivalent strain </p>

Contrary to the claims of numerous reports over the last two decades, there does not yet exist a viable plasma sputtering method for complex oxides such as the lead- and bismuth-containing perovskites. In fact, the lack of reproducibility in any vapor deposition means for such materials is the primary reason why the promise of nonvolatile ferroelectric RAM (FeRAM) has delivered so little over the last two decades, with only low-density devices being provided, instead, by solution and mist techniques (via both sol-gel and MOD). In part, the present work provides the first comprehensive treatment of the challenges present in the plasma sputter deposition of ferroelectric strontium bismuth tantalate (SBT), with SBT thin films fabricated under a wide variety of deposition approaches. As such, ferroelectric SBT was successfully formed by the primary plasma sputtering methods used for ferroelectric materials in the past; namely, R.F. sputtering of ceramic targets and D.C. reactive sputtering of metal targets. Capacitors were fabricated to establish the ferroelectric properties of the SBT films. The approach allows for new insights into phase formation in the SBT system. The inadequacies of the previous sputtering approaches used for ferroelectrics (as well as High Tc superconductors) are highlighted in the context of their inherent run-to-run instability. Subsequently, there is developed a new and rather fundamental vapor deposition technique, termed Electron-Assisted Deposition (EAD), which provides uniquely non-equilibrium growth conditions. This terminology is founded in the direct contradistinction of the presently developed process with previously developed Ion-Assisted Deposition (IAD) processes. The developed EAD process provides the first means by which metallic-mode reactive sputtering, wherein the desired compound is formed by surface reactions at the film's growth interface, can be implemented for a ferroelectric or, in fact, the multicomponent perovskites, in general. In addition to other benefits, such metallic-mode sputtering is found to be inherently more stable and reproducible than the previously used ceramic-target and poisoned-target approaches.

This research was instigated to study non-equilibrium segregation effects during the crystallization of a glass. The non-equilibrium segregation coefficient has been experimentally measured in a variety of alloys including silicon and it has been observed to increase by orders of magnitude as a function of growth rate. Monte Carlo modeling has successfully simulated this effect and has led to the analytical Jackson equation which describes it. Glass crystallization usually takes place far from equilibrium and glasses have the advantage that the glass-crystal interface does not move during quenching, and so the segregation effects can be evaluated at room temperature. The germanium in silica system was chosen for this study because germanium should substitute for the silicon and the glass matrix, and diffuse slowly enough in silica to permit evaluation of the non-equilibrium segregation. Samples were prepared by implanting silica glass with germanium, and then annealing to permit diffusion and to promote crystallization. The samples were analyzed with RBS before and after annealing to determine the distribution of germanium. Initially, the implanted germanium peak was observed to shift towards the surface which is attributed to ion drift in an electric field. This effect was eliminated with a pre-anneal which incorporated the germanium ions into the glass matrix. Since the non-equilibrium segregation depends on the dopant diffusion rate, the diffusion coefficient of germanium in amorphous and crystalline silica was measured. The diffusion coefficient in the silica glass was found to be DG=47exp(-5.8x 10⁴/T) cm²/s and the diffusion coefficient in the silica crystal was found to be DC=360exp(-(6.9x 10⁴/T)) cm²/s . The non-equilibrium segregation coefficient was evaluated based on the distribution of the dopant after crystallization, including the build-up of dopant at the crystal/glass interface. When fitted to the Jackson equation the equilibrium distribution coefficient was found to be k(eq) = 0.01. The non-equilibrium segregation coefficient increased with crystallization rate.

The advancement of IC technology has led to an increasing demand for faster and cheaper microelectronic devices. One of the key processing steps in fabricating ultra-large scale integration devices is copper chemical-mechanical planarization (CMP). Traditional copper CMP slurries use hydrogen peroxide as an oxidant. A novel copper CMP slurry based on hydroxylamine chemistry is being considered as an alternative to hydrogen peroxide based slurries. The main goal of the research reported in this dissertation is to understand the removal of copper in hydroxylamine based chemistries. Copper removal experiments were performed on a regular CMP tool and a specially designed electrochemical abrasion cell (EC-AC). The effects of applied pressure and abrasion speed were investigated on both tools. The electrochemistry of copper in hydroxylamine based chemistry was investigated using electrochemical techniques on the EC-AC tool. The techniques include electrochemical polarization and voltammetry. The effects of solution pH and hydroxylamine concentration on the polarization of copper were systematically investigated. The fate of hydroxylamine and other nitrogen-based species were studied using capillary electrophoresis chromatography. The removal rates of copper obtained from a regular CMP tool were twice as much as the rates obtained from the EC-AC tool. However, the removal rates from both tools showed the same trend with respect to pH. Interestingly, a maximum peak in copper removal rates occurs at a pH value of 6, and a significant decrease in rates occur at pH values deviating from 6. The copper removal results obtained from the EC-AC tool with and without abrasion showed that the high removal rate at pH 6 is largely due to chemical attack. The reactions involved in the oxidation of copper are dependent on the decomposition and complexation behaviors of hydroxylamine. Electrochemical analysis showed the removal of copper may be dependent on the reduction of nitric oxide (NO) to hyponitrous specie (H₂N₂O₂). Capillary electrophoresis chromatography analyses showed the consumption of hydroxylamine and species generated from the autooxidation/reduction of hydroxylamine. In slightly alkaline pH conditions, the removal of copper was predominantly due to mechanical abrasion of the surface oxide. This was supported by the potential-pH diagrams and the analysis of applied pressure and relative velocity. At pH values ranging from 3 to 5, the removal of copper was due to oxidation of Cu to Cu²⁺.

The electrochemical deposition of copper has been a major focus of research for decades. Renewed interest in copper electroplating is not limited to the copper producers but is also a major concern of semiconductor manufacturers. The focus on copper electrochemistry by the semiconductor manufacturers has increased since IBM's announcement in 1997 that copper will be used for metallization in high speed/power semiconductors [1--3]. The desire to use copper instead of aluminum is simply a reflection on copper's superior conductivity (lower RC time constants) and resistance to electromigration (generally proportional to the melting point). This dissertation is the compilation of the research into analytical techniques for monitoring surface-active additives in common sulfuric acid/copper sulfate plating baths. Chronopotentiometric, DC and AC voltammetry were the major analytical techniques used in this research. Several interactions between the additives will also be presented along with their apparent decline in activity. The decline in activity is well known in the industry and is also detected by these methods as presented in chapters 4 and 5. Finally, a systemic approach for monitoring the additive Galactosal, which is commonly used in electrowinning, will be outlined. The monitoring system proposed herein would have to be adjusted for each electrowinning facility because each has a unique chemistry and cell configuration.

Organic light-emitting devices (OLEDs) are traditionally patterned either through vacuum deposition masks or by UV lithographs. However, such patterning routes are relatively expensive, time consuming, and geometry limited. On the other hand, developments in the use of inkjet printing as a tool to pattern a given electrode promise a low cost, maskless, and non-contact approach to generate a myriad of patterns. In this dissertation, I will present our exploratory works in ink jet printing techniques, to pattern conductive polymers for use as electrodes with predefined shapes and controlled conductivity. Our works have been extended to explore printing with multiple inks, which mix and/or react with each other, for the use in making artificial muscles and for the developments of inkjet combinatorial techniques. Many factors including surface tension of the printed solution, substrate surface properties, and drying conditions have a direct effect on the final quality and performance of the organic based devices. Issues related to device fabrication on flexible substrates will be discussed and the results of tested devices are shown.

Recent experimental efforts have focused on the development of water-based chemistries to deposit hydrophobic alkylsilane films on the silica surfaces to address the problem of stiction induced failure in MEMS. A detailed molecular level examination of the structure of these films is limited with the available experimental methods. Therefore, this work undertakes an investigation of the structure and properties of self-assembled alkylsilane monolayer films via Monte Carlo (MC), and molecular dynamics (MD) simulations. The existing literature on the surfactant aggregation is used as a guide for modeling the alkylsilanes molecules. However, the current literature is ambiguous whether to describe interactions between the surfactant head groups as short-range or long-range. This work resolves this discrepancy successfully by performing a series of simulations of various structural and interaction models of surfactants. Simulations show that a realistic surfactant aggregation requires an excluded volume of the head groups, necessitating different interaction models in different structural models of surfactants. Next, MC simulations have been used to investigate the impact of the charged group in cationic alkylsilane on the structure of the deposited film. The structure of the films is characterized with the spatial pair correlations at each molecular layer of the deposited films. The long-range correlations are seen for the films of cationic alkylsilanes. Also, the frictional behavior of the alkylsilane films deposited on silica substrates is examined via molecular dynamics simulations. The friction coefficients of the films are obtained as a function of separation between the films, temperature, and velocity of the substrates. The results of the MD simulations support a thermal activation model of friction.

Fracture in brittle materials under a macroscopic load, results from the propagation of atomic-scale defects/cracks under the influence of a local stress field. These local stress fields are significantly higher than the macroscopic stress applied, causing local rearrangement of atoms around the crack tip and a consequent straining of atomic bonds that ultimately break, leading to separation of the material. The brittle fracture process has been a subject of many simulations and experiments, but the exact nature of atomic rearrangement that occurs in the regions of high stress has not yet been clearly identified. Thus, a primary objective was to accurately characterize the atomic restructuring in these critical regions. The method of molecular dynamics (MD), a widely used atomistic computation tool, was used to study the atomic-scale dynamics that take place during fracture of a typical brittle material---amorphous silica (a-SiO2). The interatomic interactions were represented by potential functions derived from first-principles. The effects of charge-transfer and temperature on the fracture process of a-SiO2 samples of different densities were investigated as a function of uniaxial strain-rates (0.1/ps-0.005/ps). A mechanism involving growth and coalescence of voids previously identified to underlie the process of brittle fracture was studied in detail in this thesis as a function of interatomic potential function, charge transfer and temperature. The regions surrounding these voids were found to be characterized by edge-sharing silica tetrahedra, while the rest of the material retained the bulk structure (corner-sharing tetrahedra) of silica glass. A secondary objective of this research work was to develop multiscale methodologies capable of modeling typical 'materials' problems like fracture. A global representation of the fracture process needs a seamless coupling of techniques capable of modeling different length and time scales. Specifically, far away from the critical regions, where the system is in elastic conditions, it is computationally prudent as well as scientifically elegant to use continuum-level simulation schemes like finite elements (FE) and finite difference time domain methods (FDTD) rather than atomistics, and only use atomistic simulations to model the highly strained regions. In this work, a continuum-FDTD region was coupled to an atomistic-MD region to study the propagation characteristics of a stress wave with broadband spectral features. The 'mismatch' in the coupling was quantified by analyzing the amount of reflection of the probing wave from the FDTD-MD interface. The above described work forms the basis for future fracture studies.

This dissertation contains studies on some aspects of the media and system in the optical data storage. The main subjects that have been examined are the magneto-optical (MO) media, phase-change (PC) media, and the effect of substrate birefringence on the optical system used in recording and readout. In the studies of the MO media, we concentrate on the magnetic properties of the groove edge (sidewall) and compute the coercivity caused by the edge of a terrace. Comparing the computer-simulation results with data obtained from the Kerr-loop measurement, we realize the distribution of the easy axis for films with oblique deposition. Concerning the material characterization, we employ the micro-Hall effect measurements to trace the domain-size variation during the thermomagnetic recording process. In the investigations of phase-change media, a new technique to determine the specific heats, thermal conductivities, and phase-transition temperature for non-erasable media is developed. On the subject of substrate birefringence, we describe a novel method to measure the substrate's vertical birefringence. We also examine the effects of birefringence on the signal obtained in an MO readout system as well as the image contrast in magnetic domain observations through the substrate.

The present investigation is concerned with the processing and characterization of sol-gel derived Polyceram materials. Polycerams, a new class of multi-functional materials, are organic-inorganic composite materials where the components are combined at or near the molecular level. In this dissertation, particular emphasis is attributed to the synthesis, processing and characterization of thin films of Polycerams. Numerous optical characterization techniques were performed to study the passive properties of Polycerams, including index of refraction, optical attenuation, UV transmission and surface embossing. Dielectric waveguides of superior optical quality were obtained and Polycerams proved to be surface patternable with near-perfect shape replication abilities. The above properties are discussed in conjunction with a scattering model which explains the structural homogeneity of Polycerams. Optical losses below 0.15 dB/cm and the simple fabrication of channel waveguides and lenses via surface embossing render Polycerams highly suitable candidates for today's integrated optics technology.