Date of Award

1-2-1993

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physics & Astrophysics

Abstract

A review of the theoretical framework necessary for the description and calculation of electronic transport characteristics in two dimensional Bismuth Tellurium Sulfide (BTS) is given. The processes for preparing and cooling one quintuple layer BTS samples to temperatures of approximately one Kelvin are described.BTS samples with a conductance greater then e$\sp2$/h are shown to demonstrate weak antilocalization effects and magnetoconductance that are dependent upon the sample temperature and the applied electric field. BTS samples with a conductance much less than e$\sp2$/h are shown to demonstrate strong localization and variable range hopping (VRH) effects and magnetoconductance that are dependent upon the sample temperature and the applied electric field in a manner similar to that in the weak localization regime. In both the weak and strong localization regimes it is shown that the temperature dependence of the magnetoconductance can be suppressed by a strong electric field. The characteristic magnetic field values for the dominant scattering processes in both weak and strong localization regimes are found by fitting digamma functions to experimental data. The absence of h/e periodicity in VRH is observed. A dominant linear magnetic field dependence of the magnetoconductance for low applied magnetic fields in the VRH regime is shown. The mixing of weak and strong localization mechanisms in the moderately localized regime is reported. Evidence for the Coulomb blockade in tunneling processes for very high resistance BTS samples is presented. The Coulomb blockade is used to partially explain the inability to fit BTS magnetoconductance curves to the present theories for the dependence of the magnetoconductance on temperature and electric field.

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