Tikhonov, Alexander
(2007)
I. Theory of Laser Driven Molecular Wires.II. Light Diffraction by Colloidal Crystals - Numerical Simulations for Realistic Finite Systems Using Single Scattering Theory.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Part I considers electron transport through a molecular bridge coupled to two metal electrodes in the presence of a monochromatic ac radiation field. Coherent current flow through the wire is calculated within a nondissipative one-electron tight binding model of the quantum dynamics. Using Floquet theory, the field-driven molecular wire is mapped to an effective time- independent quantum system characterized by a tight-binding Hamiltonian with the same essential structure as the nondriven analog. Thus, the Landauer formalism and scattering Green's Function methods for computing current flow through the wire, which have been profitably applied to the molecular wire problem in the absence of driving, can also be used to analyze the corresponding field-driven system.The theory developed here is applied to an experimentally relevant system, namely a xylyl-dithiol molecule in contact at either end with gold electrodes. Net current through the wire is calculated for two - STM and molecular junction - configurations of the electrode-wire-electrode system for a range of experimental inputs, including bias and the intensity and frequency of the laser. Via absorption/emission of photons, the electron tunneling occurs through an interference of many pathways and may lead to a significantly enhanced laser-driven current at experimentally accessible laser field strengths.In Part II we apply a single particle scattering methodology to calculate diffraction efficiencies of finite Crystalline Colloidal Arrays (CCA's). We developed an extension of the well-known Kinematic theory and tested it by comparing computed light scattering efficiencies with exact results for 1D slab model. We discuss some applications of the method to finite CCA's of different shapes and sizes. In particular, the dependence of diffraction intensities on the incident angle is analyzed near the Bragg diffraction maximum for several different crystal planes. We also study the effect of the incident beam shape and cross sectional profile on the CCA diffraction. Finally, the effective penetration depth for the incident light is calculated and compared for several incident directions, and the effect of stacking faults on diffraction efficiencies is analyzed using the methodology developed herein.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
29 January 2007 |
| Date Type: |
Completion |
| Defense Date: |
27 October 2006 |
| Approval Date: |
29 January 2007 |
| Submission Date: |
16 November 2006 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Dietrich School of Arts and Sciences > Chemistry |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
molecular electronics; nanoscale transport junction; photonic crystals; driven electronic transport; driven tunneling |
| Other ID: |
http://etd.library.pitt.edu/ETD/available/etd-11162006-140646/, etd-11162006-140646 |
| Date Deposited: |
10 Nov 2011 20:05 |
| Last Modified: |
15 Nov 2016 13:51 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/9688 |
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