This dissertation explores the synthesis and characterization of phosphine stabilized tetrel (group 14) cations. Tetrel cations are readily generated by reacting a halogermane or halostannane with a Lewis acid to generate an in situ germylium, stannylium cation or an in situ germyldiylium, stannyldiylium dication. A Lewis base such as a phosphine is added to the mixture to produce the corresponding salt with dative P-Sn or P-Ge connectivity. Tin and germanium salts represent new as well as unique cationic structures for phosphorus containing species. The preparation of these salts is proven to be generalizable, reproducible, and can be isolated as pure materials in moderate to high yields.

Thesis (Ph. D.)--University of Pennsylvania.

Thesis (Ph. D.)--University of Pennsylvania, 1932.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1962. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1955. / Typescript. Vita. With this are bound 2 reprints from Physical review: Effective masses of holes in silicon / R.N. Dexter ... and Benjamin Lax ... Vol. 96, no. 1 (1 Oct. 1954), p. [223] -- Anisotropy of cyclotron resonance of holes in germanium / R.N. Dexter ... H.J. Zeiger and Benjamin Lax ... Vol. 95, no. 2 (15 July 1954), p. 557-558. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Pennsylvania.

Thesis (M.S. of electrical engineering)--Washington State University, December 2006. / Includes bibliographical references (p. 17).

Th.--Sci. phys.--Toulouse 3, 1977. N°: 786.

An investigation of the metal-nonmetal transition in arsenic-doped germanium (Ge;As) has been performed using the technique of nuclear magnetic resonance. The host Ge73 resonance has been observed in twelve, single crystal, uncompensated specimens with room-temperature carrier concentrations from 7.1016-1.75.1019cm−3. Measurements of the nuclear spin-lattice relaxation time T1, Knight shift K and the nuclear linewidth △B for Ge73 are reported. Specifically, data are given at and below liquid helium temperatures for an applied magnetic field of 1. 44T and at 4.2K alone at a field of 5T. The Knight shifts have been measured at 4.2K at 5T and values of △B are given for both fields at 4.2K. The T1 measurements at low field (1.44T) and Knight shift results show donor density dependences of free-electron type. A strong field dependence of T1 has however been observed which is inexplicable by free-electron theory. The resonance linewidths are greater than the nuclear dipolar value, even for non-metallic samples, and increase with doping density and magnetic field. At the critical concentration for transition to metallic behaviour K shows an abrupt change from zero to a finite value. The low-field T1's are in contrast continuous across the transition but the high-field T1's do show a sharp increase below the critical doping density. A calculation shows spin diffusion to be unimportant for the samples and other mechanisms which can generate a field-dependent relaxation time are discussed. Firstly, assuming that the electrons form a homogeneous system and are confined to a narrow impurity band parameterised by an appropriate Bohr radius leads to a field dependence of T1 in order of magnitude agreement with the data. A second qualitative model in line with recent ideas on the origin of negative magnetoresistance in doped semiconductors invokes the presence of nearly-free moments or Kondo centres in addition to the itinerant electron system. The fluctuation of the moments can furnish a relaxation process in addition to that due to Fermi contact between band electrons and nuclei. An increase in magnetic field inhibits the moment fluctuation rate and thus increases with field. Moreover the presence of moments will lead to resonance line broadening as we have observed. Finally, the magnetic properties of an Anderson transition are discussed and the abrupt appearance of K is shown to be consistent with Mott's interpretation of an Anderson transition. An important overall result is that the electron-electron effects observed in Si:P are absent in the Ge:As system. Simple estimates show that the intra-atomic correlation energy is smaller in n-Ge than n-Si and it is concluded that the metal-nonmetal transition in Ge:As is of Anderson-type and that correlation plays no essential role. This proposal is shown to be in agreement with the results of other experiments in heavily-doped Ge.

This investigation is concerned with a study of the properties of scandium-germanium systems, and a study of the properties of selenium and zinc doped gallium arsenide„ In part one the physical properties of scandium and germanium are used to empirically estimate the relative solubility of scandium in germanium. It was shown that scandium and germanium are miscible in the liquid phase and that scandium has a very low solid solubility in germanium. Crystals of scandium-doped germanium were grown and analyzed using Hall constant and resistivity measurements from liquid nitrogen temperature to room temperature. The results show that the crystals grown are p-type, but that this behaviour cannot be completely attributed to scandium. However, it was shown that if scandium does not form compounds on crystal growth, it has a maximum solubility in germanium of less than one part per million. Methods for analysing the results of experimental measurements, to determine the concentration of acceptors, donors and free carriers, and the ionization energies are given. In part two the properties of selenium and zinc doped gallium arsenide were studied, again using resistivity and Hall measurements. Selenium and zinc were determined to be shallow donors and acceptors respectively. The concentration of the impurities present were determined and the properties of the material were discussed. / Science, Faculty of / Physics and Astronomy, Department of / Graduate