Thesis (M.S. in Applied Physics)--Naval Postgraduate School, December 2009. / Thesis Advisor(s): Karunasiri, Gamani. Second Reader: Smith, Craig. "December 2009." Description based on title screen as viewed on January 28, 2010. Author(s) subject terms: Zinc Selenide, photodetectors, ultraviolet, Schottky, responsivity, current-voltage, depletion region, bandgap, melanoma, dark current, forward biased, reverse biased. Includes bibliographical references (p. 39-40). Also available in print.

Thesis (Ph. D.)--University of South Florida, 2003. / Includes vita. Title from PDF of title page. Document formatted into pages; contains 204 pages. Includes bibliographical references.

Ingots containing single crystals were grown from melts of Cu, In and Se in either stoichiometric proportions (CuInSe2) or with an excess of Se (CuInSe2.2). In addition, either sodium selenide (Na 2Se) or elemental sodium (Na0) was introduced to both sets of compositions in concentrations ranging from 0 to 3 at. %. The starting constituents were placed in quartz ampoules, which were evacuated and sealed before undergoing a vertical-Bridgman growth procedure. Analysis of deposits seen on the ampoule walls and on the ingot surface after growth revealed the presence of Na, as well as various forms of the other starting elements; however, no Na was found within the crystals. Electrical measurements revealed trends in the thermoelectric power of the ingots to correspond with additions of Na, as well as the presence of excess Se. A sign conversion from p- to n-type was confirmed with addition of sodium to stoichiometric CuInSe2. A suggested mechanism used to explain the effects of Na on the material, based on these experimental observations, is presented.

Chapter 1 is the introduction to the thesis. The general principles of radical cyclisation reactions are highlighted with a focus upon the reactivity of iminyl radicals. A more detailed discussion follows on radical cyclisations onto nitriles including examples of tandem cyclisations. The final section is concerned with cyano migration reactions, and provides evidence for the reversibility of these translocations. The investigation into tandem radical cyclisations of nitriles is discussed in Chapter 2. The aim of the project was to form bicyclic nitrogen heterocycles from acyclic precursors by utilising the nitrile function as a radical acceptor which could then undergo further cyclisation onto a suitably placed alkene. We found a surprising chemoselectivity for 1,5-exo-cyclisation of alkyl, aryl and vinyl radicals onto the cyano group over 1,6-exo-cyclisation onto suitably placed alkenes. The presence of an electron-withdrawing group on the carbon a- to the nitrile group resulted in an overall 1,4-cyano migration reaction. The intermediate cyclic iminyl radical does not undergo further cyclisation, nor does it abstract hydrogen from tributyltin hydride. Instead, fragmentation by β-scission yields a stabilised radical, e.g. by an ester or nitrile group. In order to investigate the effect of substituents on the cyclisation of aryl radicals onto nitriles, and the β-scission reactions of the iminyl radical intermediates, a series of aryl radical precursors were prepared. a-Nitrile, amide, sulfone and phenyl groups favoured β-scission and a-alkyl groups favoured cyclisation or reduction of the aryl radicals. The study indicated the existence of a Thorpe-Ingold effect on the cyclisation of aryl radicals onto nitriles. In Chapter 3 the largely unsuccessful studies of the reversibility of radical cyclisations onto nitriles is reported. Finally, in Chapter 4, the results obtained from our research into vinyl radicals as precursors for tandem radical cyclisations of nitriles are presented. A vinyl iodide underwent complete conversion when standard radical cyclisation conditions were applied; the cyclic ketone resulting from a single 5-exo cyclisation was isolated in the absence of any other products. The experimental relevant to the discussion is detailed in Chapter 5.

Thesis (M.Mat.S.E.)--University of Delaware, 2008. / Principal faculty advisor: Robert W. Birkmire, Dept. of Materials Science & Engineering. Includes bibliographical references.

Thesis (Ph. D.)--University of Hong Kong, 2008. / Also available in print.

Thesis (Ph. D.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains xv, 200 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 194-200).

Cadmium sulfide and cadmium selenide are important materials for applications such as photoconductive cells, photovoltaic cells and other electrooptical devices. Generally, these devices use single crystals. However, reasonable efficiencies have been observed by using polycrystalline films on conducting substrates, which are easier to make and provide considerable savings on materials and energy. Polycrystalline CdS/CdSe films have been made by sputtering and solution spraying, compound evaporation, chemical vapor deposition, and many others. A recent technique involves the electrochemical deposition of CdS and CdSe from nonaqueous solvents. Preparation of these films is based upon the cathodic deposition from a nonaqueous solution of a cadmium salt and elemental sulfur and/or selenium. Although the technique is simple, no mechanistic information is known to optimize the conditions in which films of controlled stoichiometry, doping and crystallinity are made. This research has the purpose to understand the mechanism of the formation of polycrystalline films of CdS and CdSe by electrochemical deposition in dimethylsulfoxide. This approach to the problem makes use of electrochemical techniques such as rotating ring disc electrode, linear scan voltammetry, high pressure liquid chromatography coupled with ultraviolet and electrochemical detection. By the rotating ring disc electrode technique, we have studied the kinetic parameters for the reduction of sulfur, selenium, cadmium, and the electroChemical formation of CdS and CdSe for temperatures from 25 - lOO°C. The results show that rates of initie.l electron transfer for the reduction of these species are moderately rapid, and secondly, that the reverse reaction is irreversible and involves additional steps. Studies of solubility of selenium with temperature reveal that its solubility is enhanced by the addition of sulfur. Understanding the electrochemical behavior of sulfur-selenium mixtures is of great importance to produce mixed semiconductive films with more adequate bandgaps for use with solar spectrum. Electrochemistry of sulfur-selenium mixtures are no different from that of sulfur alone. High pressure liquid chromatography separations with spectroscopic and electrochemical detectors have shown that sulfur solutions contain 86 and 87 fractions which are not electrochemically active.

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