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.

A transportation method was used to evaluate the activity coefficients of the minor elements, As, Bi, Pb, and Sb, in both Cu - Fe and Ni - Cu mattes, white metal, and molten Ni₃S₂ as a function of their concentration. Values for the activity coefficients are compared to values obtained by other investigators. With the Cu - Fe mattes and white metal, the analysis was conducted at Cu/Fe molar ratio between 1 to ∞, at sulfur deficiencies from -0.02 to +0.02, and at temperatures between 1493 and 1573 K. Activities of As and Sb in the melts are both concentration dependent at weight percents less than 0.3. No such dependency is observed for Bi or Pb. First and second order self interaction parameters are also reported for As and Sb in Cu - Fe matte. With the Ni-Cu mattes only the sulfur deficiency and the Ni/Cu molar ratio were varied. The experiments were conducted at 1473 K at Ni/Cu molar ratios of ∞, 2, and 1, and at SD values from 0 to -0.1. As and Sb are substantially more stable in Ni - Cu mattes than in Cu - Fe mattes, while for Pb and Bi the presence of Ni does not change the activity of Pb and Bi significantly. The Henrian activity coefficients of these minor elements in both Cu - Fe and Ni - Cu mattes are reported. (Abstract shortened by UMI.)

The adsorption of selected surfactants and inorganic ions of interest to semiconductor processing onto metallic, semiconductor, and dielectric surfaces has been investigated using a quartz crystal microbalance (QCM) technique. The effects of variables such as solution pH and concentration on the extent of adsorption have been characterized. Improvement of the sensitivity of the technique using an electrical bias to the crystal electrode has been explored. The etch rate of sputter coated silicon, sputter coated silica, and thermally grown silica of interest to semiconductor processing has been investigated using a thickness shear mode (TSM) quartz crystal microbalance (QCM) technique. In this research, silicon and sputtered silica and low temperature thermal oxide were investigated in ammonia peroxide solutions using a quartz crystal microbalance. The results obtained have been compared with the literature results to show that a QCM is a valuable in situ measurement technique to follow low levels of etch rate. In an application of the QCM technique to the chemical mechanical polishing (CMP) process, the static etch rate and chemical mechanical polishing rate of an Al-1%Si-0.5%Cu alloy were investigated in abrasive-free solutions containing a proprietary amine at alkaline pH values. The effect of lixiviant, oxidizing agents, complexing agents, temperature, and applied pressure on polishing behavior were investigated. The results have shown that it is possible to polish aluminum alloy films with a high degree of selectivity over SiO2 using abrasive-free amine based solutions containing a glycine based complexing agent.

This study was undertaken with the goal of comparing the calculated nucleation rate for phase separation with experimental measurements for a simple glass system. The magnitude and the temperature dependence of the nucleation rate for a sodium silicate glass composition in the binodal regime was calculated. These calculations used a minimum of assumptions in order to determine the limits on certain thermodynamic variables, chiefly surface energy. Many of the values used in these calculations were determined from growth and coarsening measurements made on this system. Nucleation rates, as well as growth and coarsening rates, were then measured in this system for this comparison to theory. It was found that the free energy of mixing models are unable to predict nucleation behavior at temperatures near the immiscibility boundary. In addition, these models predict that the nucleating composition lies outside of the binodal. Although the values measured for the activation energy correspond well to those in the literature, their incorporation into the nucleation expression does not correct for the temperature behavior of the free energy of mixing. It is also unlikely that a temperature dependent surface energy term could account for the poor predictive nature of classical nucleation theory at small undercoolings.

Jackson, Gilmer and Temkin used a Spin-1 kinetic Ising model to simulate non-equilibrium binary alloy solidification. In this dissertation the detailed relationship of this model to the solidification of binary alloys is reported. The phase transformation kinetics of the model is investigated as a function of growth rate, surface roughness, liquid diffusivity, equilibrium segregation coefficient, entropy of fusion, and composition of the liquid. Simulations for pure silicon predict a growth rate dependence on orientation and undercooling in accord with experimental results. Simulation results for the binary material show an increase in the non-equilibrium segregation coefficient (k(neq)) with surface smoothness, growth velocity and decreasing liquid diffusivity. Simulations for the orientation and growth velocity dependence of the segregation coefficient are in accord for experimental results for the solidification of bismuth doped silicon due to Aziz et al. Simulation results on the dependence of k(neq) on the equilibrium segregation coefficient, k(eq) are also consistent with experiment. The non-equilibrium segregation coefficient was found to increase with concentration of the liquid, but the effect is small at low concentrations.

Stereodeposition is a freeform fabrication technique which accomplishes the computer-controlled, layerwise buildup of an object through direct placement of a fluid which rapidly solidifies. Current materials compatible with stereodeposition include functional ceramics and metals, engineering polymers, and composites. The key to this flexibility is stereodeposition's ability to operate under a wide range of liquid-to-solid transformation rates. Understanding and controlling the material parameters involved in the liquid-to-solid transition is critical, as solidification ultimately impacts the precision and quality of the final object. A model of the liquid-to-solid transition has been developed in which a bead spreading on a curved surface is followed as a series of state "snapshots", whereby an applied force produces an incremental bead motion in an increment of time. This approach differs from most liquid spreading models, but allows flexibility in the time and geometry dependence of forces associated with a solidifying stereodeposition liquid. The model predicts bead contact angle as a function of time based on initial liquid properties (surface tension, viscosity, yield strength) and the solidification strategy employed, namely rheology control, mass transfer, or thermal transfer. Three parameter groupings are identified: alpha, which controls final contact angle, beta, which controls spreading rate, and delta, which controls amount of liquid transformation occurring during spreading. To validate the model, dynamic measurements are performed on the spreading of slurries of silica particles in various liquids. The model is found to predict the early stage of spreading (5 s) under one of the two proposed boundary conditions, and is shown to be equivalent in the limit to the more traditional dynamic wetting models employing an energy rate balance. An explanation is presented for the failure of the model to accurately predict the final contact angle for highly shear-thinning slurries.

Solid freeform fabrication (SFF) methods enable the creation of new structures with multiple materials. While the ability to put any material in any location during the building process allows the freedom to create most any combination, it does not readily suggest the best combination for a given task. The performance demands of a structural member differ from those of a sensor and hence would have different criteria for optimal structures. The methods used herein begin to show how the interaction of the different materials impacts their performance experimentally and can be modeled to determine preferred structures. In this work structures were formed by SFF comprising multiple materials with two areas examined: metal-ceramic monoliths and embedded polymer sensors within composite structures. The Metal-ceramic monoliths consisted of a SFF ceramic preform which was subsequently infiltrated with metal resulting in a graded structure, pure ceramic on one side and nearly pure metal on the other. These structures showed improved toughness over pure ceramic structures when tested in bending. Different metal-ceramic interface gradings were modeled based on the experimental samples, including variations of ceramic content. The model showed that the optimal structure was dependent on the orientation during mechanical testing, or application, as well as the ceramic content of the monolith. Embedded poly vinylidene fluoride (PVF2) sensors were used to monitor internal stresses in composite systems. The PVF2 sensors were shown to be capable of detecting damage over the range light tapping to severe impact. More importantly the sensors were able to detect barely visible impact damage (BVID), which can lead to deterioration of mechanical performance without visible evidence. Additionally the PVF2 sensors were used to monitor cure of epoxy systems by sensing the modulus of the matrix. It was shown that for a fixed impact level the sensor response varied as the relative modulus of matrix to sensor changed. Modeling confirmed that when the sensor modulus is much higher than the matrix the stress level in the sensor is higher. The model also showed that the stress level in the sensor is dependent on the geometry and loading, with smaller sensors performing better.

As the MOS devices continue to scale down in feature size, the gate oxide thickness is approaching the nanometer node. High leakage current densities caused by tunneling is becoming a serious problem. Replacing silicon oxide with a high kappa material as the gate dielectrics is becoming very critical. In recent years, research has been focused on a few promising candidates, such as ZrO₂, HfO₂, Al₂O₃, Ta₂O₅, and some silicates. However, unary metal oxides tend to crystallize at relatively low temperatures (less than 700°C). Crystallized films usually have a very small grain size and high leakage current due to the grain boundaries. The alternatives are high κ oxides which are single crystal or amorphous. Silicates remain amorphous at high temperatures, but have some problems such as phase separation, interface reaction, and lower κ value. In this work, we addressed the crystallization problems of zirconium oxide and hafnium oxide thin films. Both of these two thin films were deposited by DC reactive magnetron sputtering so that very dense films were deposited with little damage. A specially designed system was set up in order to have good control of the deposition process. The crystallization behavior of as-deposited amorphous ZrO₂ and HfO₂ films was studied. It was found that the films tended to have higher crystallization temperature when the films were thinner than a critical thickness of approximately 5 nm. However, it was still well below 900°C. The crystallization temperature was significantly increased by sandwiching the high kappa oxide layer between two silica layers. Ultra thin HfO₂ films of 5nm thickness remained amorphous up to 900°C. This is the highest crystallization temperature which has been reported. The mechanisms for this effect are proposed. Electrical properties of these high kappa dielectric films were also studied. It was found that ultra thin amorphous HfO₂ and ZrO₂ films had superior electrical properties to crystalline films. The leakage current density of ultra thin amorphous films was at least two orders of magnitude lower than that of crystallized films. Amorphous films also showed much less hysteresis in the capacitance-voltage curve than uncapped crystallized films. The mechanisms for the electrical property differences between ultra thin crystalline and amorphous films were studied. Due to successful control of the low dielectric interfacial layer thickness, an effective oxide thickness of 1.2 and 1.4 nm was obtained for HfO₂ and ZrO₂ films, respectively.

A modification of Scherer's Self-Consistent model and a new model, the Interlocking Cell model, have been developed to characterize the sintering behavior of mixtures of two glass powders. The theoretical sintering curves predicted by both these models are compared to each other and to experimental densification behaviors. Viscosities extrapolated from homogeneous sintering curves of sol-gel derived powders are transient and cannot be predicted based on composition alone. These transient viscosities have a significant effect on the sintering kinetics. The Self-Consistent and Interlocking Cell models assume very different microstructural changes during sintering. However, differences between the two models can just be distinguished using experimental densification curves of sol-gel cordierite based glass mixtures.