Theoretical Studies on Quantum Transport Through Individual Extended Metal Atom Chains with Three Metal Atoms
Date Issued
2010
Date
2010
Author(s)
Huang, Qian-Rui
Abstract
This master thesis is partitioned in three chapters: “Introduction”, “Charge transport through individual trinuclear EMACs” and “Bias dependence of intensities in the transmission spectra of single-molecule junctions”.
Charge Transport Through Individual Trinuclear EMACs
Charge Transport properties of single-molecule junction based on trinuclear extended metal atom chains (EMACs) are investigated using the Non-Equilibrium Green’s Function method and the extended Huckel theory. We identify the major conducting orbitals of the trichromium, tricobalt and trinickel complexes, which directly explain the trend in the single-molecule conductance. While the metal cores allow almost all of the current flow through, the conjugated ligands has the function to tune the conducting ability of the EMACs instead of provides another conducting pathways. Moreover, we have proposed a molecular orbital interpretation to the periodic trend in the single-molecule conductance of EMACs with the first-row transition metal cores, which illustrate the strong connections among the conductance, the orbital energies, the atomic number and the metal-metal bond order.
Bias Dependence of Intensities in the Transmission Spectra of
Single-molecule Junctions
The modification of transport properties in single-molecule junctions in the region of finite bias is investigated by the Non-Equilibrium Green’s Function (NEGF) method and the first-order perturbation theory. Combining these two theories, we derive a semiquantitative formula in terms of molecular orbital coefficients to estimate the variation of transmission functions under the bias. The influence of bias for the symmetric and nonsymmetric junctions on the intensities of transmission functions is clarified. Finally, we applied this analysis to the following systems, a Huckel model system and two real single-molecule junctions, which consist of naphthalenedithiol and azulenedithiol, demonstrating the bias-induced change of the intensities of transmission functions.
Subjects
Quantum Transport
Molecular Electronic
EMACs
Single-molecule conduction
Bond Order
Type
thesis
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