The semiconductor industry has decreased silicon-based device feature sizes dramatically over the last two decades for improved performance. However, current technology has approached the limit of achievable enhancement via this method. Therefore, other techniques, including introducing stress into the silicon structure, are being used to further advance device performance. While these methods produce successful results, there is not a proven reliable method for stress and strain measurements on the nanometer scale characteristic of these devices. The ability to correlate local strain values with processing parameters and device performance would allow for more rapid improvements and better process control. In this research, x-ray diffraction and convergent beam electron diffraction have been utilized to quantify the strain behavior of simple and complex strained silicon-based systems. While the stress relaxation caused by thinning of the strained structures to electron transparency complicates these measurements, it has been quantified and shows reasonable agreement with expected values. The relaxation values have been incorporated into the strain determination from relative shifts in the higher order Laue zone lines visible in convergent beam electron diffraction patterns. The local strain values determined using three incident electron beam directions with different degrees of tilt relative to the device structure have …

I have used computer simulations to investigate the behavior of polymeric materials at the molecular level. The simulations were performed using the molecular dynamics method with Lennard-Jones potentials defining the interactions between particles in the system. Significant effort was put into the creation of realistic materials on the computer. For this purpose, an algorithm was developed based on the step-wise polymerization process. The resulting computer-generated materials (CGMs) exhibit several features of real materials, such as molecular weight distribution and presence of chain entanglements. The effect of the addition of a liquid crystalline (LC) phase to the flexible matrix was also studied. The concentration and distribution of the second phase (2P) were found to influence the mechanical and tribological properties of the CGMs. The size of the 2P agglomerates was found to have negligible influence on the properties within the studied range. Moreover, although the 2P reinforcement increases the modulus, it favors crack formation and propagation. Regions of high LC concentration exhibit high probability of becoming part of the crack propagation path. Simulations of the tensile deformation under a uniaxial force have shown that the molecular deformation mechanisms developing in the material depend on several variables, such as the magnitude of …

The increasing use of polymer-based materials (PBMs) across all types of industry has not been matched by sufficient improvements in understanding of polymer tribology: friction, wear, and lubrication. Further, viscoelasticity of PBMs complicates characterization of their behavior. Using data from micro-scratch testing, it was determined that viscoelastic recovery (healing) in sliding wear is independent of the indenter force within a defined range of load values. Strain hardening in sliding wear was observed for all materials-including polymers and composites with a wide variety of chemical structures-with the exception of polystyrene (PS). The healing in sliding wear was connected to free volume in polymers by using pressure-volume-temperature (P-V-T) results and the Hartmann equation of state. A linear relationship was found for all polymers studied with again the exception of PS. The exceptional behavior of PS has been attributed qualitatively to brittleness. In pursuit of a precise description of such, a quantitative definition of brittleness has been defined in terms of the elongation at break and storage modulus-a combination of parameters derived from both static and dynamic mechanical testing. Furthermore, a relationship between sliding wear recovery and brittleness for all PBMs including PS is demonstrated. The definition of brittleness may be used as …

Dan Beaty (1937-2002) was a prolific composer, pianist, researcher, educator, and writer. His large compositional output included chamber works, choral works, songs, orchestral pieces, electronic music, and keyboard works. Beaty was well versed in traditional Western music as well as the more avant-garde and perplexing idioms of the twentieth century. Beaty's compositions reflect the many fascinating, if not always popular, musical trends of his time. His music encompasses styles from serial to jazz, shows compositional influences from Arnold Schoenberg to Indonesian music, and demonstrates thought-provoking and highly intellectual craftsmanship. This document explores several of Beaty's songs through a discussion of the composer's life and compositional process. Songs included in this document are Three Weeks Songs, October, November, A Sappho Lyric, Love Song, That Night When Joy Began, and War Lyrics. This document was written to accompany the author's DMA Lecture-Recital at the University of North Texas. Unfortunately, Beaty's vocal music was never published and is mostly unknown. One goal of the project was to initiate interest in Beaty's songs. Through this document, Lecture-Recital, and additional performances, considerable strides have been made to bring Beaty's songs to new audiences throughout the United States. In addition, the author has received permission from …

Tissue response to PNIPAM and HPC nanoparticles has been studied by implantation method. The results suggest that both PNIAPM and HPC nanoparticles possess good biocompatibility and they may serve as a good carrier for the applications of controlled delivery. Rheological properties of dispersions of IPN microgels composed of PNIPAM and PAAc have been studied. It is found that the IPN microgel dispersion can undergo a sol-gel transition at temperature above 33°C. In vivo drug release experiments suggest that the gelation procedure creates a diffusion barrier and thus leads to slow release. An emulsion method has been used to grow columnar crystals by mixing PNIPAM microgel dispersions with organic solvents. Effect of both temperature and microgel concentration on formation of columnar crystals has been studied. PNIPAM-co-NMA microgels have been used for the fabrication of crystalline hydrogel films by self-crosslinking microgels. The hydrogel film exhibits an iridescent. The thermally responsive properties and mechanical properties of this film have been studied. Melting temperature (Tm) of colloidal crystals self-assembled with PNIPAM-co-AAc microgels has been investigated as a function of pH, salt concentration and microgel concentration. It is revealed that Tm increases as pH value increases; Tm decreases with increase of salt concentration; Tm increases …