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Recent developments in semiconductor physics have led to a new field of study, namely the study of nanostructures. Nanostructures are the future for electronic devices. In this project the conductance of electrons through nanostructures will be considered. The structures examined in this project are similar in design. The goal will be to examine the conductance through these structures.The methodology in use for finding the conductance of a nanostructure is the recursive Green's function method. This includes finding the transverse eigenvalues and eigenfunctions and computing hopping integrals to determine the Green's propagators. The conductance is obtained following these steps. For the numerical calculations a structured FORTRAN computer program was developed.As stated earlier, the future electronic devices will utilize the developments of conductance through components having dimensions on the nanometer scale. These dimensions, theoretically, will allow faster operation and smaller units. The theoretical development of this project will propagate the knowledge and understanding of conductance in this regime. / Department of Physics and Astronomy

Future electronic devices having dimensions on the nanometer scale will rely on the resultant quantum effects for their operation. In this project, these quantum effects were investigated through the theoretical modeling and computer simulation of a confined twodimensional electron gas in a semiconductor heterostructure. Assuming hardwall boundaries and sharp geometrical features, the nanostructure conductance has been calculated by finding transverse eigenvalues and eigenfunctions, computing hopping integrals for a one-dimensional tight binding lattice, determining the Greens' propagators, and then finally evaluating the transmittance. From the transmittance, the conductance was determined.A structured and modular computer program in FORTRAN was developed to investigate the effects of geometrical modifications on the conductance of ballistic nanochannels. The program has been designed in such a way that the user need only supply the nanostructure specifications to an input data file. The program then uses this data file to perform the calculations. A separate, user-friendly program has been developed to form the data file. The program is such that additions and modifications can be easily made in the future. / Department of Physics and Astronomy

The electronic transport properties in low dimensional systems have several important features which have attracted a wide range of both experimental and theoretical interests. The quantum ballistic transport regime in these small systems is achieved when dimensions of systems are less than the elastic mean free path and the phase coherent length. We have studied electron transport in a nanochannel, containing repulsive delta impurities. To find the conductance, a recursive Green's function method is used. The study includes finding the transverse eigenvaiues, eigenfunctions, and computing hopping integrals to determine the Green's propagators.The effects of the number, and position of the repulsive delta impurities with various potential strengths on the conductance in a nanostructure have been presented. A FORTRAN program has been used and developed for the numerical calculations. The general practical applications for nanostructures include the ability to make electronic devices smaller, denser and operate at very low voltages. The future electronic devices will utilize the developments of conductance through components having dimensions on the nanometer scale. / Department of Physics and Astronomy

Multiple longitudinal potential barriers affect electron transport in a nanostructure. In addition to a symmetric, aperiodic quantum wire with five potential barriers, a quantum wire containing thirteen potential barriers was modeled based on a quasiperiodic sequence known as the Fibonacci sequence. Conductance of the wires and transmission coefficients of the corresponding one-dimensional systems were calculated and analyzed in this work.Conductance calculations were performed using a FORTRAN computer program, tbgf, which performs the tight-binding, recursive Green's function method. Also Program Tran Coeffwas developed in order to calculate one-dimensional transmission coefficients using the method known as wavefunction matching. This method matches electronic wavefunctions in neighboring regions to determine the one-dimensional transmission coefficients at the electron energy normalized to the barrier strengths. The program uses the data file generated by Program Data Input. / Department of Physics and Astronomy

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thèse (M.Sc.)--Université Laval, 2007. / Bibliogr.: f. 114-117. Publié aussi en version électronique dans la Collection Mémoires et thèses électroniques.