Portland State College. Department of Physics
Date of Award
Master of Science (M.S.) in Physics
1 online resource (83 leaves)
Field emission, Bismuth
An experimental search based on previous published theoretical work was made for de Haas-van Alphen-like quantum oscillations in field emission current. The study was motivated by the possible applicability of de Haas-van Alphen measurements to the study of Fermi surfaces near real surfaces, Field emitters were fabricated from bismuth single crystals grown from the melt by a modified Bridgeman technique. Field emission current was measured with the field emitter cooled by contact with a liquid helium bath. Most measurements were made at 4.2° K, although a few measurements were made at 2.02°K; Fowler-Nordheim plots of the experimental current-voltage data were linear over several orders of magnitude. The field emission current was measured as a function of magnetic field strength to twenty kilogauss and as a function of direction, with respect to the emitter axis, for a steady field of ten kilogauss. The results of measurements on four field emitter crystals are reported in this thesis. In most of this work, de Haas-van Alphen-like quantum oscillations were not observed. In one set of data, however, de Haas-van Alphen-like oscillations having a period of 0.50 x 10⁻⁵ G⁻¹ appear to be present. The published theoretical work was reevaluated. As a result of a large effective Dingle temperature for field emitters, and because the effective masses of carriers in bismuth are anisotropic, the de Haas-van Alphen effect in field emission current could be several times smaller than has been suggested in the literature. The sensitivity of the experiments reported in this thesis was not sufficient to allow unambiguous identification of quantum oscillations at the reduced level. An outline of an experimental procedure suitable for observation of the de Haas-van Alphen-like effect in field emission current at the reduced level is provided in the final chapter.
Casey, Donald Dean, "Search for quantum oscillations in field emission current from bismuth." (1968). Dissertations and Theses. Paper 575.