Download or read book Charge Transport in Molecular Junctions with Novel Two dimensional Contacts written by Shuhui Tao and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Charge Transport in Molecular Junctions written by Michele Kotiuga and published by . This book was released on 2015 with total page 195 pages. Available in PDF, EPUB and Kindle. Book excerpt: Here, we use and develop first-principles methods based on density functional theory (DFT) and beyond to understand and predict charge transport phenomena in the novel class of nanostructured devices: molecular junctions. Molecular junctions, individual molecules contacted to two metallic leads, which can be systematically altered by modifying the chemistry of each component, serve as test beds for the study of transport at the nanoscale. To date, various experimental methods have been designed to reliably assemble and mea- sure transport properties of molecular junctions. Furthermore, theoretical methods built on DFT designed to yield quantitative agreement with these experiments for certain classes of molecular junctions have been developed. In order to gain insight into a broader range of molecular junctions and environmental effects associated with the surrounding solution, this dissertation will employ, explore and extend first-principles DFT calculations coupled with approximate self-energy corrections known to yield quantitative agreement with experiments for certain classes of molecular junctions. To start we examine molecular junctions in which the molecule is strongly hybridized with the leads: a challenging limit for the existing methodology. Using a physically motivated tight-binding model, we find that the experimental trends observed for such molecules can be explained by the presence of a so-called "gateway" state associated with the chemical bond that bridges the molecule and the lead. We discuss the ingredients of a self-energy corrected DFT based approach to quantitatively predict conductance in the presence of these hybridization effects. We also develop and apply an approach to account for the surrounding environment on the conductance, which has been predominantly ignored in past transport calculations due to computational complexity. Many experiments are performed in a solution of non-conducting molecules; far from benign, this solution is known to impact the measured conductance by as much as a factor of two. Here, we show that the dominant effect of the solution stems from nearby molecules binding to the lead surface surrounding the junction and altering the local electrostatics. This effect operates in much the same way adsorbates alter the work function of a surface. We develop a framework which implicitly includes the surrounding molecules through an electrostatic-based lattice model with parameters from DFT calculations, reducing the computational complexity of this problem while retaining predictive power. Our approach for computing environmental effects on charge transport in such junctions will pave the way for a better understanding of the physics of nanoscale devices, which are known to be highly sensitive to their surroundings.
Download or read book Charge and Exciton Transport through Molecular Wires written by Laurens D. A. Siebbeles and published by John Wiley & Sons. This book was released on 2011-07-18 with total page 293 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Molecular Switches written by Ben L. Feringa and published by John Wiley & Sons. This book was released on 2011-08-04 with total page 814 pages. Available in PDF, EPUB and Kindle. Book excerpt: Täglich benutzen wir Schalter, um strombetriebene Geräte an- und abzuschalten und kein Compuer würde ohne sie funktionieren. Nach den gleichen Prinzipien funktionieren auch molekulare Schalter, die unter dem Einfluß ihrer Umwelt zwischen zwei definierten Zuständen wechseln können. Im Gegensatz zu den gewöhnlichen Schaltern sind molekulare Schalter aber außerordentlich klein und ihre Anwendung in der Nanotechnologie, Biomedizin und im Computerchipdesign öffnet neue Horizonte. Im vorliegenden Zweibänder berichten Herausgeber und Autoren über molekulare Schalter aus Katenanen und Rotaxanen, Fulgiden, Flüssigkristallen und Polypeptiden. Die Bandbreite der behandelten Themen reicht von chiroptischen Schaltern über multifunktionale Systeme bis hin zu molekularen logischen Schaltungen. Chemiker und Materialwissenschaftler in Industrie und Hochschule, die sich für einen der innovativsten Bereiche ihrer Wissenschaft interessieren, werden dieses Buch mit Gewinn lesen!
Download or read book Fabrication and Characterization of Electrical Contacts for Charge Transport Study in Molecular Electronics written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Formation of Two Dimensional Supramolecular Structures and Their Use in Studying Charge Transport at the Single Molecule Level at the Liquid Solid Interface written by Sepideh Afsari Mamaghani and published by . This book was released on 2015 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Modulation and Control of Charge Transport Through Single Molecule Junctions written by Kun Wang and published by . This book was released on 2016 with total page 326 pages. Available in PDF, EPUB and Kindle. Book excerpt: Building electronic devices out of single molecules has been the ultimate goal of downscaling electric circuits. Understanding charge transport through single-molecule junctions is central to achieving this goal. To gain deeper insights into charge transport through single molecules, this dissertation centers on detailed experimental modulation and control of charge transport through single-molecule junctions using modified scanning probe microscope break-junction (SPM-BJ) techniques. First, I explored the effect of molecule-electrode contact interfaces. Using force-conductance cross-correlation analysis, I mapped out the correlation between conductance and force of modulated Au-octanedithiol-Au junctions measured with CAFM-BJ. The investigation of the conductance change during junction elongation showed a unique contact tunneling barrier of octanedithiol, which was interpreted by a newly developed contact barrier model. A systematic control of anchoring groups of benzene-based molecular junctions showed that current rectification occurred whenever asymmetric anchoring groups were introduced, which is mainly due to asymmetry in potential drop across the contacts. Second, I studied the impact of DNA's structural change on its conductance. The conductance of poly d(GC)4 DNA duplex was found to decrease by two orders of magnitude during a B- to Z-form structural transition, which is mainly attributed to the breaking of Ï0-Ï0 stacking between adjacent base pairs caused by the transition. Using stretch-hold mode STM-BJ technique, the structural transition was successfully monitored solely based on conductance measurements. Then, I attempted to modify the structure of DNA for functional I-V feature. A DNA-based molecular rectifier was for the first time constructed by site-specific intercalation of coralyne molecules into a custom-designed DNA duplex. Measured I-V curves of the resulting DNA-coralyne complex showed strong rectification with a rectification ratio of 15 at 1.1V. Based on NEGF-DFT calculations, this rectification is mainly caused by asymmetric coupling of the HOMO-1 level to the electrodes when an external bias is applied, an unprecedented rectification mechanism. Finally, Fermi level pinning of charge transfer resonances was investigated in junctions composed of terthiophene containing molecular wires. Taken together, these results not only provide new understanding of charge transport through molecules, they also opened new route for building functional molecular electronic devices.
Download or read book Electrochemical Engineering for the 21st Century Dedicated to Richard C Alkire written by H. Deligianni and published by The Electrochemical Society. This book was released on 2010-10 with total page 117 pages. Available in PDF, EPUB and Kindle. Book excerpt: The papers included in this issue of ECS Transactions were originally presented in the symposium ¿Electrochemical Engineering for the 21st Century (dedicated to Richard C. Alkire)¿, held during the 217th meeting of The Electrochemical Society, in Vancouver, Canada, from April 25 to 30, 2010.
Download or read book Mechanical Control of Charge Transport and Chemical Reactivity in Molecular Junctions written by Leopoldo Meja̕ Restrepo and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Charge transport plays a critical role in a wide range of molecular processes including photosynthesis, redox catalysis, energy storage, biological signaling, and the operation of molecular electronic devices. Understanding and controlling these key events requires establishing how molecular structure influences charge transport and designing physically realizable strategies to manipulate them. This thesis advances the theory, simulation, and interpretation of charge transport experiments in molecular junctions and identifies novel avenues to use external mechanical stimuli to control chemistry and physics in this nanoscale setting. The reason why we focus on molecular junction experiments is because they enable the manipulation of individual molecules and the characterization of their response to external stimuli such as mechanical forces, bias voltages, and electro-magnetic fields. Such a controllable setting is ideal to establish structure-charge transport relations at the single-molecule limit that can inform and resolve the individual molecular contributions to bulk phenomena. We first demonstrate that conductance can act as a sensitive probe of conformational dynamics during the mechanical pulling of molecular junctions. These advances offer an efficient solution to experimentally monitor conformational dynamics at the single-molecule limit. Next, we bridge molecular conductance with mechanochemistry and investigate how to mechanically onset and electrically monitor chemical reactivity in single molecules. In particular, we demonstrate mechanically controlled association and rupture reactions in molecular junctions and show that simultaneous measurements of force and conductance are able to signal reactive events that cannot be distinguished by force or conductance alone. The computations are based on atomistic molecular dynamics and nonequilibrium Green's functions computations of electron transport. At the methodological level, we clarify the utility of the Landauer equation for computing charge transport across molecular junctions immersed in a thermal environment such as solvent. The Landauer equation is central to the modeling of molecular electronics experiments. However, it supposes that the current is coherent (solely due to quantum tunneling) and does not capture the possible influence of the environment in the net current. We isolate physical conditions that require an analysis beyond Landauer and use them to identify chemical motifs capable of stabilizing coherent, incoherent, and intermediate transport mechanisms. Molecular junction experiments typically record the conductance of thousands of freshly formed junctions and report histograms of conductance events. Here, we construct a microscopic theory of such conductance histograms by merging the theory of force spectroscopy developed in biophysics with molecular conductance. The theory enhances the information that can be extracted from molecular electronics experiments, and can be employed to develop schemes to narrow the width of the histograms as desirable for spectroscopic applications and molecular device design. Further, the theory opens key opportunities to atomistically model the conductance histograms, as needed to bridge the gap between theory and experiments."--Pages viii-ix.
Download or read book Understanding and Engineering Molecular Interactions and Electronic Transport at 2D Materials Interfaces written by Chih-Jen Shih (Ph. D.) and published by . This book was released on 2014 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt: 2D materials are defined as solids with strong in-plane chemical bonds but weak out-of-plane, van der Waals (vdW) interactions. In order to realize potential applications of 2D materials in the areas of optoelectronics, surface modification, and complex materials, there are many engineering challenges associated with understanding and engineering molecular interactions at 2D materials interfaces, which requires understanding and engineering multiscale physical phenomena. With this in mind, the goal of this thesis has been to combine continuum modeling, molecular dynamics (MD) simulations, chemical synthesis, and device fabrication to understand and engineer molecular interactions at 2D materials interfaces at different length scales. The three main topics considered include: (i) wetting behavior of graphene (micrometer scale), (ii) solution processing of graphene and graphene oxide (nanometer scale), and (iii) electronic modification in graphene and molybdenum disulfide (atomic scale). The first part of my thesis investigates the wetting behavior of graphene-coated surfaces. Based on the classical theory of van der Waals interactions, monolayer graphene acts like a "nonlinear translucent" barrier, transmitting about 30% of the original water-substrate interactions through it. The contact angle on a graphene-coated substrate is determined by both liquid-graphene and liquid- substrate interactions. This, in turn, results in different degrees of "wetting transparency". By combining theoretical analysis, MD simulations, and contact angle measurements, I show that monolayer graphene becomes more "transparent" to wetting on hydrophilic substrates and more "opaque" to wetting on hydrophobic substrates. The second part of my thesis develops a fundamental understanding and engineering strategies to disperse graphene and graphene oxide in a liquid phase. The mechanism of stabilization of liquid-phase exfoliated graphene sheets in polar solvents is investigated using potential of mean force (PMF) calculations and MD simulations. Along with a kinetic theory of colloid aggregation, the graphene sheets are predicted to aggregate based on thermodynamic arguments. Because of the different affinities of various solvents for the surface of graphene, efficient solvents can enhance the stability of the graphene sheets by: (i) reducing the depth of the vdW well, and (ii) increasing the energy barrier. Using the calculated PMF curves associated with different solvents, with only one adjustable parameter, the kinetic theory is able to predict the lifetimes of graphene sheets, including ranking the five solvents considered in terms of their ability to stabilize graphene. In addition, I present an advanced concept for the layer-controlled production of pristine large graphene dispersions. The use of ionic graphite intercalation compounds to produce Stage-2 and Stage-3 graphite intercalation compounds (GICs) are shown to be excellent precursors for the production of bilayer and tri-layer graphene dispersions. When combined with an on-chip separation method, a population of large area graphene flakes is produced, such that conventional photolithography is enabled for top-gate device fabrication. My present approach enables the only viable route at this time to produce AB stacked bi- and tri-layer graphene on arbitrary substrates on a large scale. Moreover, a comparative study that combines experiments and MD simulations is carried out to understand the effects of pH on the colloidal stability and surface activity of graphene oxide (GO) aqueous solutions. The reported pH-dependent behavior originates from the degree of deprotonation of the carboxyl groups at the edge of GO sheets. At low pH, the carboxyl groups are protonated, such that the GO sheets become less hydrophilic and form suspended GO aggregates. The GO aggregates formed at lower pH are found to be surface active and do not exhibit the salient critical-micelle-concentration (CMC) feature associated with the formation of surfactant micelles. At higher pH, the carboxyl groups are deprotonated and the strong hydrophilicity of the edge carboxyl groups pulls the GO sheets into bulk water, making GO behave like a regular salt dissolved in water. A series of surface tension measurements further suggests that GO does not behave like a conventional surfactant in both pH 1 and pH 14 aqueous solutions. The third part of my thesis develops engineering strategies to modify electronic characteristics of graphene using molecular adsorption, covalent functionalization, and a molybdenum disulfide (MoS2) - graphene heterojunction. I investigate the effects of surfactant adsorbates on transport characteristics in graphene transistors. The surfactant adsorbates are found to: (i) transfer electrons to graphene, (ii) scatter carrier transport, and (iii) induce more electron-hole puddles on the SiO2 substrate. The mechanism behind the unusually observed behaviors can be rationalized using a new theoretical model based on the self-consistent transport theory. I find that the change in transport characteristics is surfactant-dependent, and results from the interactions between the surfactant adsorbates, graphene, and the underlying SiO2 . In addition, I demonstrate an efficient method to covalently functionalize monolayer and bilayer graphene (MLG and BLG) in a precise and controllable manner using electrochemical aryl diazonium chemistry. Using this method, for the first time, I study the transport characteristics of bottom-gated MLG and dual-gated BLG field effect transistor (FET) devices as a function of the degree of functionalization, which provides insight on the electronic transport in functionalized graphene. I show that the electronic transport in functionalized graphene is limited by the formation of electron-hole puddles and mid-gap states due to chemical functionalization. A more significant transport band gap can be created in functionalized BLG at a highly positive transverse electric displacement field. Moreover, I investigate charge transfer, photoluminescence, and gate-controlled electronic transport in the junction between two 2D materials - MoS2 and graphene. Without applying any transverse electric fields, there is a significant number of electrons transferred from MoS2 to graphene due to their work function difference. The charge transfer also results in the formation of a Schottky barrier at the interface, increasing interlayer impedance between the two materials. Despite the interlayer impedance, the quantum yield for MoS2 in the heterostructure is still considerably quenched, since the hot carriers generated in MoS2 during photoexcitation can overcome the barrier readily, subsequently being collected by the adjacent graphene layer. I fabricate FET devices comprised of the MoS2 - graphene heterostructure, and show that the interlayer impedance can be further manipulated by the gate and drain voltages, demonstrating a new type of FET device, which enables a controllable transition from NMOS digital to bipolar characteristics. I show that an on/off current ratio ~100 can be achieved without sacrificing the field-effect electron mobilities in graphene. This thesis advances our understanding on how to engineer molecular interactions at 2D materials interfaces. Specifically, I demonstrate that by combining continuum theory, MD simulations, chemical synthesis, and device fabrication, one can elucidate the multiscale physics underlying these interactions, and further propose new engineering approaches to overcome the associated challenges. There is ample opportunity and need for the combined theoretical and experimental studies in this emerging field to understand and design these nanoscale materials for various electronic, energy, and environmental applications. As reflected in this thesis, it is hoped that the interactive connections between theories and experiments, as well as the engineering innovations driven by multiscale understanding, will significantly facilitate the development of 2D materials commercialization.
Download or read book Two dimensional Molecular Self assembly Approaches to Nanoelectronics written by John Duc Le and published by . This book was released on 2006 with total page 474 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Single Molecule Electronics written by Manabu Kiguchi and published by Springer. This book was released on 2016-05-23 with total page 239 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a multidisciplinary approach to single-molecule electronics. It includes a complete overview of the field, from the synthesis and design of molecular candidates to the prevalent experimental techniques, complemented by a detailed theoretical description. This all-inclusive strategy provides the reader with the much-needed perspective to fully understand the far-reaching ramifications of single-molecule electronics. In addition, a number of state-of-the-art topics are discussed, including single-molecule spectro-electrical methods, electrochemical DNA sequencing technology, and single-molecule chemical reactions. As a result of this integrative effort, this publication may be used as an introductory textbook to both graduate and advanced undergraduate students, as well as researchers with interests in single-molecule electronics, organic electronics, surface science, and nanoscience.
Download or read book Internal Photoemission Spectroscopy written by Valeri V. Afanas'ev and published by Elsevier. This book was released on 2014-02-22 with total page 404 pages. Available in PDF, EPUB and Kindle. Book excerpt: The second edition of Internal Photoemission Spectroscopy thoroughly updates this vital, practical guide to internal photoemission (IPE) phenomena and measurements. The book's discussion of fundamental physical and technical aspects of IPE spectroscopic applications is supplemented by an extended overview of recent experimental results in swiftly advancing research fields. These include the development of insulating materials for advanced SiMOS technology, metal gate materials, development of heterostructures based on high-mobility semiconductors, and more. Recent results concerning the band structure of important interfaces in novel materials are covered as well. Internal photoemission involves the physics of charge carrier photoemission from one solid to another, and different spectroscopic applications of this phenomenon to solid state heterojunctions. This technique complements conventional external photoemission spectroscopy by analyzing interfaces separated from the sample surface by a layer of a different solid or liquid. Internal photoemission provides the most straightforward, reliable information regarding the energy spectrum of electron states at interfaces. At the same time, the method enables the analysis of heterostructures relevant to modern micro- and nano-electronic devices as well as new materials involved in their design and fabrication. First complete model description of the internal photoemission phenomena Overview of the most reliable energy barrier determination procedures and trap characterization methods Overview of the most recent results on band structure of high-permittivity insulating materials and their interfaces with semiconductors and metals
Download or read book Molecular Architectonics written by Takuji Ogawa and published by Springer. This book was released on 2017-07-06 with total page 535 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book draws on the main themes covered during the International Workshop on Molecular Architectonics which took place in Shiretoko, Japan from August 3 to 6, 2015. The concepts and results explored in this book relate to the term “molecular architectonics” which stands for electronic, optical and information-processing functions being orchestrated by molecular assemblies. This area is defined as the third stage of single-molecule electronics and builds on stage one, where measurements were performed on single-molecule layered films, and stage two, the resulting quantitative analyses. In this work, experts come together to write about the most important aspects of molecular architectonics. This interdisciplinary, visionary and unique book is of interest to scientists working on electronic materials, surface science and information processing sciences using noise and fluctuation.
Download or read book Quantum Transport written by Supriyo Datta and published by Cambridge University Press. This book was released on 2005-06-16 with total page 434 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the conceptual framework underlying the atomistic theory of matter, emphasizing those aspects that relate to current flow. This includes some of the most advanced concepts of non-equilibrium quantum statistical mechanics. No prior acquaintance with quantum mechanics is assumed. Chapter 1 provides a description of quantum transport in elementary terms accessible to a beginner. The book then works its way from hydrogen to nanostructures, with extensive coverage of current flow. The final chapter summarizes the equations for quantum transport with illustrative examples showing how conductors evolve from the atomic to the ohmic regime as they get larger. Many numerical examples are used to provide concrete illustrations and the corresponding Matlab codes can be downloaded from the web. Videostreamed lectures, keyed to specific sections of the book, are also available through the web. This book is primarily aimed at senior and graduate students.
Download or read book Molecular Scale Electronics written by Xuefeng Guo and published by John Wiley & Sons. This book was released on 2020-07-02 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt: Provides in-depth knowledge on molecular electronics and emphasizes the techniques for designing molecular junctions with controlled functionalities This comprehensive book covers the major advances with the most general applicability in the field of molecular electronic devices. It emphasizes new insights into the development of efficient platform methodologies for building such reliable devices with desired functionalities through the combination of programmed bottom-up self-assembly and sophisticated top-down device fabrication. It also helps to develop an understanding of the device fabrication processes and the characteristics of the resulting electrode-molecule interface. Beginning with an introduction to the subject, Molecular-Scale Electronics: Concept, Fabrication and Applications offers full chapter coverage on topics such as: Metal Electrodes for Molecular Electronics; Carbon Electrodes for Molecular Electronics; Other Electrodes for Molecular Electronics; Novel Phenomena in Single-Molecule Junctions; and Supramolecular Interactions in Single-Molecule Junctions. Other chapters discuss Theoretical Aspects for Electron Transport through Molecular Junctions; Characterization Techniques for Molecular Electronics; and Integrating Molecular Functionalities into Electrical Circuits. The book finishes with a summary of the primary challenges facing the field and offers an outlook at its future. * Summarizes a number of different approaches for forming molecular-scale junctions and discusses various experimental techniques for examining these nanoscale circuits in detail * Gives overview of characterization techniques and theoretical simulations for molecular electronics * Highlights the major contributions and new concepts of integrating molecular functionalities into electrical circuits * Provides a critical discussion of limitations and main challenges that still exist for the development of molecular electronics * Suited for readers studying or doing research in the broad fields of Nano/molecular electronics and other device-related fields Molecular-Scale Electronics is an excellent book for materials scientists, electrochemists, electronics engineers, physical chemists, polymer chemists, and solid-state chemists. It will also benefit physicists, semiconductor physicists, engineering scientists, and surface chemists.
Download or read book Molecular Electronics written by Juan Carlos Cuevas and published by World Scientific. This book was released on 2010 with total page 724 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a comprehensive overview of the rapidly developing field of molecular electronics. It focuses on our present understanding of the electrical conduction in single-molecule circuits and provides a thorough introduction to the experimental techniques and theoretical concepts. It will also constitute as the first textbook-like introduction to both the experiment and theory of electronic transport through single atoms and molecules. In this sense, this publication will prove invaluable to both researchers and students interested in the field of nanoelectronics and nanoscience in general. Molecular Electronics is self-contained and unified in its presentation. It may be used as a textbook on nanoelectronics by graduate students and advanced undergraduates studying physics and chemistry. In addition, included are previously unpublished material that will help researchers gain a deeper understanding into the basic concepts involved in the field of molecular electronics.
