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This molecule has two stable conformations (cis and trans) in its electronic ground state, with considerable differences in their conductance. The electron transport properties were calculated using first-principles methods combining non-equilibrium Green's function (NEGF) techniques with density functional theory (DFT). For the azobenzene studies, we included electron-donating groups and electron-withdrawing groups in meta- and ortho- positions with respect to the azo group. The results showed that the molecular structure is crucial in optimizing the electron transport properties of chemical structures, and that the transport properties in electronic devices at the molecular level can be manipulated, enhanced or suppressed by a careful consideration of the effects of chemical modification.
A molecular wire is an organic molecule that forms a conducting bridge between electronic contacts. Single molecules are likely to be the smallest entities to conduct electricity and thus molecular wires present many interesting challenges to fundamental science as well as enormous potential for nanoelectronic technological applications. A particular challenge stems from the realization that the properties of molecular wires are strongly influenced by the Combined characteristics of the molecule and the metal contacts. While gold has been the most studied contact material to date, interest in molecular wires with transition metal contacts that ar e electronically more complex than gold is growing. This thesis presents a theoretical investigation of electron transport and associated phenomena in molecular wires with transition metal contacts. An appropriate methodology is developed on the basis of Landauer theory and Ab initio and semi-empirical considerations and new, physically important systems are identified. Spin-dependent transport mechanisms and device characteristics are explored for molecular wires with ferromagnetic iron contacts, systems that have not been considered previously, either theoretically or experimentally. Electron transport between iron point contacts bridged by iron atoms is also investigated. Spin-dependent transport is also studied for molecules bridging nickel contacts and a possible explanation of some experimentally observed phenomena is proposed. A novel physical phenomenon termed Strong spin current rectification and a new controllable negative differential resistance mechanism with potential applications for molecular electronic technology are introduced. The phenomena predicted in this thesis should be accessible to present day experimental techniques and this work is intended to stimulate experiments directed at observing them.
As functional elements in opto-electronic devices approach the singlemolecule limit, conducting organic molecular wires are the appropriate interconnects that enable transport of charges and charge-like particles such as excitons within the device. Reproducible syntheses and a thorough understanding of the underlying principles are therefore indispensable for applications like even smaller transistors, molecular machines and light-harvesting materials. Bringing together experiment and theory to enable applications in real-life devices, this handbook and ready reference provides essential information on how to control and direct charge transport. Readers can therefore obtain a balanced view of charge and exciton transport, covering characterization techniques such as spectroscopy and current measurements together with quantitative models. Researchers are thus able to improve the performance of newly developed devices, while an additional overview of synthesis methods highlights ways of producing different organic wires. Written with the following market in mind: chemists, molecular physicists, materials scientists and electrical engineers.
This thesis presents three different investigations of materials systems, with possible applications in the area of molecular electronics. Specifically, the binding of glycine, the simplest amino acid, to diamond surfaces, and the quantum transport characteristics of two prototypical metal/semiconductor interfaces are investigated. With density functional theory based simulations, we have investigated the binding of the amino acid glycine on two of the most prominent diamond surfaces, i.e. C(100) and C(111) (2x1)- with a focus on the associated energetics, charge transfer, electronic, and structural characteristics. With regards to the dimerized C(100) surface, interaction is mostly via the amide group of the glycine molecule (both with and without H-atom abstraction) and via a cycloaddition reaction whose activation barrier has been estimated via quantum chemistry methods. In contrast, the C(111) (2x1) surface was found to be mostly inert with respect to interactions with the glycine molecule. Second part of this thesis presents theoretical investigations of electronic transport devices at atomic scale. One such device is a capacitance made of atomic wires, for which we present the results of ab initio investigation of the capacitance of Al nanowires. The systems considered include cross sectional areas for the wires: Al(100)(3x3), Al(100)(5x5), and Al(100)(7x7). First principles estimates of capacitance matrix coefficients for the systems are provided. In the second part of this thesis, we have characterized the fully self-consistent electronic properties of a prototypical metal/nanotube interface using a combined nonequilibrium Greens function and density functional theory based formalism, under different conditions of gate and bias voltages. Both carbon and boron nitride nanotubes between Al electrodes, were considered. The electronic properties of the interface are dominated both by a dipole and by metal induced gap states (MIGS) formed through the transfer of.
Molecular Electronics is self-contained and unified in its presentation. It can be used as a textbook on nanoelectronics by graduate students and advanced undergraduates studying physics and chemistry. In addition, included in this new edition are previously unpublished material that will help researchers gain a deeper understanding into the basic concepts involved in the field of molecular electronics.
Modern Methods for Theoretical Physical Chemistry of Biopolymers provides an interesting selection of contributions from an international team of researchers in theoretical chemistry. This book is extremely useful for tackling the complicated scientific problems connected with biopolymers' physics and chemistry. The applications of both the classical molecular-mechanical and molecular-dynamical methods and the quantum chemical methods needed for bridging the gap to structural and dynamical properties dependent on electron dynamics are explained. Also included are ways to deal with complex problems when all three approaches need to be considered at the same time. The book gives a rich spectrum of applications: from theoretical considerations of how ATP is produced and used as ‘energy currency’ in the living cell, to the effects of subtle solvent influence on properties of biopolymers and how structural changes in DNA during single-molecule manipulation may be interpreted. · Presents modern successes and trends in theoretical physical chemistry/chemical physics of biopolymers · Topics covered are of relevant importance to rapidly developing areas in science such as nanotechnology and molecular medicine · Quality selection of contributions from renowned scientists in the field
Authored by leading experts from around the world, the three-volume Handbook of Nanostructured Thin Films and Coatings gives scientific researchers and product engineers a resource as dynamic and flexible as the field itself. The first two volumes cover the latest research and application of the mechanical and functional properties of thin films an
Advances in Molecular Nanotechnology Research and Application / 2012 Edition is a ScholarlyEditions™ eBook that delivers timely, authoritative, and comprehensive information about Molecular Nanotechnology. The editors have built Advances in Molecular Nanotechnology Research and Application / 2012 Edition on the vast information databases of ScholarlyNews.™ You can expect the information about Molecular Nanotechnology in this eBook to be deeper than what you can access anywhere else, as well as consistently reliable, authoritative, informed, and relevant. The content of Advances in Molecular Nanotechnology Research and Application / 2012 Edition has been produced by the world’s leading scientists, engineers, analysts, research institutions, and companies. All of the content is from peer-reviewed sources, and all of it is written, assembled, and edited by the editors at ScholarlyEditions™ and available exclusively from us. You now have a source you can cite with authority, confidence, and credibility. More information is available at http://www.ScholarlyEditions.com/.