This thesis presents the results of a combined cathodoluminescence (CL) and electron paramagnetic resonance (EPR) spectroscopic study of quartz from the uranium-mineralized Athabasca Basin. CL imaging not only distinguishes detrital quartz grains from their secondary overgrowths but also is able to differentiate two generations of overgrowths in the Athabasca sandstones. Moreover, the Athabasca quartz samples are characterized by three types of bright CL: 1) haloes around U- and Th-bearing mineral inclusions, 2) patches associated with U-bearing minerals in matrices or pores and 3) continuous rims in samples with or without any visible U-bearing minerals. These three types of bright CL are all of constant widths of ~35-45 Ým, indicative of bombardments of alpha particles emitted from the 238U, 235U and 232Th decay series. CL spectral analyses show that the radiation damaged areas, relative to their undamaged hosts, are characterized by intense but broad emission bands at ~350 nm and 620-650 nm. <p>Detailed EPR measurements of the Athabasca quartz samples revealed six paramagnetic defects: one oxygen vacancy center (E1'), three silicon vacancy hole centers (O23¡V/H+(I), O23¡V/H+(II) and O23¡V/M+) and two O2¡V peroxy centers. Moreover, dissolution experiments using concentrated HF showed that that the silicon vacancy hole centers and the peroxy centers are concentrated in the radiation-damaged rims/fractures, whereas the oxygen vacancy center (E1') is evenly distributed in quartz grains. CL and EPR data of quartz samples after isochronal annealing experiments suggest that the silicon vacancy hole centers and the peroxy centers are most likely responsible for the characteristic ultraviolet CL and the red CL, respectively. <p>CL haloes in detrital quartz grains are ubiquitous in the Athabasca sandstones. CL patches are also widespread but are best developed in altered sandstones close to the unconformity or faults/fractures. Continuous CL rims, however, are more restricted in occurrences and are best developed at the high-grade Cigar Lake and McArthur River deposits, where they are restricted to lithological boundaries and faults and are pervasively developed in mineralized samples and associated alteration haloes close to the unconformity. At the Key Lake deposit, continuous rims occur only in mineralized samples close to the unconformity. Continuous CL rims are absent in basement rocks below mineralization, including those at the Cigar Lake and McArthur River deposits. The occurrence of radiation damages in Athabasca quartz have also been confirmed by detailed EPR measurements, which are significantly more sensitive than CL imaging. <p>Continuous CL rims on Athabasca quartz grains most likely record bombardments of alpha particles emitted from U-bearing mineralization fluids. Therefore, their associations with the unconformity, lithological boundaries and faults provide direct evidence for those structures being the pathways for mineralization fluids. The exclusive occurrence of continuous CL rims on detrital quartz grains and the abundance of U-bearing minerals in both generations of overgrowths suggest that U mineralization must have commenced during early diagenesis and continued during the formation of overgrowths. The absence of significant radiation damages in altered basement rocks supports the hypothesis that the basement was not a major source for uranium mineralization in the Athabasca basin. The common occurrence of CL haloes in euhedral quartz grains and CL patches associated with U-bearing minerals in faults, fractures and voids provide further (visual) evidence for late remobilization of uranium.

This thesis is about thermal etching of quartz single crystals with boron oxide melt and thermal etchings on inorganic polymeric single crystals of orthosilicates, willemite (Zn2SiO4) and phenakite (Be2SiO4), where isolated [SiO4] groups are polymerized by corner-sharing with other tetrahedral groups, such as [ZnO4] and [BeO4]. On the thermal etching of quartz, experiments were performed on quartz (10 0), (0001), (10 1) and (11 1) from 500¢J to 700¢J. Three types of etch figures were recognized by scanning electron microscopy: isolated dislocation etch pit, aligned etch pits and flat etch pits. The effects of defect specification and £\-£] displacive phase transformation of quartz on its development of thermal etch figures were evaluated. By doing so, boron oxide melt was proved to be a useful etchant on the studies of defect types and dynamics of quartz. As for the thermal etching of phenakite type silicate, we conducted thermal-cycle etching of willemite at 1250¢J, hydrochloric and hydrofluoric acid etchings of willemite and phenakite at room temperature, and boron oxide melt etching of willemite and phenakite at 700¢J. Surface premelting, anisotropic lattice etching and defect etching were found to play important roles on the thermal etching of willemite. Impurity segregation at dislocation outcrops on willemite (0001) should occur in the first thermal cycling in order to nucleate hillocks at the centers of the hexagonal dislocation etch pits. Reflection IR spectroscopic analysis indicated the surface premelt has the same structural units as willemite, although the subsequent crystallization follows a silica rich path. A silica-rich surface coverage impedes the etching of crystal plane underneath. There is significant polygonization and cleaving-healing of willemite single crystal upon thermal cycling according to transmission electron microscopy observation. Phenakite has remarkable chemical and thermal etching resistance in comparison to its isostructure willemite due to site energy difference of Be and Zn in coordination number 4.

Since its discovery in 2004, graphene has been widely touted as a potential replacement for silicon in the next generation of electronic circuits owing to its exceptionally high carrier mobilities and its ultra-thin body. Graphene field effect transistors (GFETs) show promising potential for use in analog and radio frequency (RF) applications, with theoretically predicted THz frequencies only being limited by fabrication challenges. High series resistance of the source/drain access regions in a GFET is one such major factor responsible for performance degradation. In this thesis, a simple and straightforward scheme of reducing this resistance by self-aligned spin-on-doping of graphene using surface transfer dopants is presented. Back-gated GFETs were fabricated on Si/SiO2 and doped using various surface transfer dopants. A novel method of spin-on-doping graphene using poly(ethyleneimine) (PEI) was developed. Top-gated GFETs with mobilities up to 6,900 cm2/Vs were fabricated and their access regions were spin-on-doped in a self-aligned manner offering a 3X reduction in the series resistance. GFET drive currents improved by up to 4X and transconductances up to 3X after self-aligned doping. GFETs were also fabricated on insulating quartz substrates with mobilities up to 5,600 cm2/Vs and showed performance enhancements up to 2X after self-aligned doping. / text

Thesis (Ph.D)--University of Wollongong, 2004. / Typescript. Includes bibliographical references: leaf 192-207.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 36-38). Also available via the Internet.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Th.--Sci. phys.--Besançon, 1979. N°: 135.

Th.--Sci. phys.--Besançon, 1979. N°: 132.

This diploma thesis deals with the oldest recognized deformation microstructure of felsic granulites of Blanský les (southern Bohemian Massif) in order to understand their lower crustal deformation history later altered during exhumation. Moreover, the study is focused on decomposition of ternary feldspars in the proto-phase of evolution of granulite microstructure. Based on the structural and microstructural analyses of the less developed cleavage I. and the more developed cleavage II., it was possible to distinguish between two deformation structures. The S1 is defined by compositional banding of alternating quartz bands with bands rich in plagioclase, garnets and with porphyroclasts of alkaline feldspars. The S1 cleavage is transposed into the S2 cleavage. During intense reworking of S1 into S2, the quartz bands were decomposed and recrystallized into the ribbons. The feldspar thermometry of the cleavage I. and II. allowed to distinguish the three stages of decomposition of feldspars. A continuous temperature decrease was observed as reflected by the individual microstructures. The quantitative microstructural analysis indicate the shape preferred orientation of the grain boundaries of two-feldspar matrix. The shape preferred orientation of cleavage I. is controlled by the albite rim, however after its...

The piezoelectric effect of quartz rich rock has been investigated both in the laboratory and a subterranean environment. In the laboratory experiment, rock specimens from the Con Mine, Northwest Territories, were examined for crystal alignment and cut into oriented 3.81 cm (1.5 in) sided cubes. The specimens were clamped, together with the measuring electrodes, between parallel plates of a compression cage designed to apply a consistent and uniform pressure distribution across the samples. A solenoid device applied a stress pulse of highly repeatable amplitude and form to the specimen and an instrumentation amplifier measured the differential piezoelectric voltage between opposite faces of the specimen. The massive samples with random fabrics were expected to yield a net "statistical effect". The measured voltage variations between orthogonal directions were attributed to signal domination by large crystals within the matrix, limited sample volume, microfracturing, and the distribution of non-piezoelectric mineral components within the matrixes of some specimens. The greatest piezoelectric responses were obtained from samples containing large crystals in their matrix. The cubic aggregates which clearly exhibited quartz crystal alignment displayed the theoretically predicted minimum piezoelectric response parallel to the preferred crystal elongation direction. The specimens exhibiting greatest alignment produced the largest piezoelectric responses. The limited experimental evidence indicated that the signal magnitude was also proportional to quartz content and crystal size. Underground trials of two exploration systems were conducted at the Con Mine In the first trial, during periods of low industrial electrical interference, clear piezoelectric signals were observed for source-target distances as large as 55 m and electrode-target distances out to 20 m. Piezoelectric signals were generated by impact of both compressional and shear seismic waves with the exposed quartz vein. While this exploration system operated quite effectively during periods of low electrical noise, a superior filter system was required for the normal conditions. For the second fields test, a more portable, DC powered, instrumentation amplifier with an extensive filter system was designed. Despite the improved filtering, noise levels were significantly higher during this trial and beyond 10 m the initial arrival of the piezoelectric signal was obscured. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate