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 Environmental Control of Charge Transport Through Single Molecule Junctions written by Brian John Capozzi and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This technique has the potential for application in nano-scale systems beyond single-molecule junctions. These results constitute another step toward the development of single-molecule devices with commercial applications. Finally, the methods presented in this thesis offer further insights into the electronic structure of molecular junctions. We show that we can assess energy-level alignment at metal molecule interfaces– this alignment is a crucial parameter controlling the proper- ties of the interface. We also demonstrate that we can probe large regions ( 2eV) of the transmission function which governs charge transport through the junction. By being able to control level alignment, we are also able to offer preliminary studies on single-molecule junctions in the resonant transport regime. Combined, the results presented in this thesis grant new insights into electron transport at the nanoscale and provide new routes for the development of functional single-molecule devices.

Download or read book Molecular Scale Electronics written by Xuefeng Guo and published by Springer. This book was released on 2018-12-06 with total page 262 pages. Available in PDF, EPUB and Kindle. Book excerpt: The series Topics in Current Chemistry Collections presents critical reviews from the journal Topics in Current Chemistry organized in topical volumes. The scope of coverage is all areas of chemical science including the interfaces with related disciplines such as biology, medicine and materials science. The goal of each thematic volume is to give the non-specialist reader, whether in academia or industry, a comprehensive insight into an area where new research is emerging which is of interest to a larger scientific audience. Each review within the volume critically surveys one aspect of that topic and places it within the context of the volume as a whole. The most significant developments of the last 5 to 10 years are presented using selected examples to illustrate the principles discussed. The coverage is not intended to be an exhaustive summary of the field or include large quantities of data, but should rather be conceptual, concentrating on the methodological thinking that will allow the non-specialist reader to understand the information presented. Contributions also offer an outlook on potential future developments in the field.

Download or read book Modulating Single Molecule Junction Conductance Through Light Bias and Temperature Stimulation written by Haipeng Li and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The continuous demand for modern electronics has been urging smaller, faster and cheaperelectronic devices. Traditional silicon-based electronics will meet inevitable fundamentallimitation once the feature size enters the quantum mechanical regime. In this work, weintroduce the concept and implementation of electronics based on single molecular junctions.The intrinsic advantages of single molecular electronics lie in the fact of low cost, smaller featuresize and unique charge transport mechanisms which are all fundamentally different fromconventional electronic devices. We start with introduction of background of charge transporttheory in a single molecular junction and the Single Molecule Break Junction (SMBJ) method tomeasure the conductance of a single molecule. Then, we demonstrate modulation of the singlemolecule conductance through light exposure, electrical bias and thermal activation. The firstsingle molecule system we study is the norbornadiene-quadricyclane (NB-QC). We demonstratethe correlation of the structure change and conductance change via a UV-exposure as well as athermally relaxation. We further discovered that the NB-QC bi-directional switching could alsobe induced with an electric bias. The forward switching (NB to QC) is due to a local heating effectdue to electron phonon coupling. The reverse switching (QC to NB) is due to a Single ElectronTransfer (SET) assisted process. Utilizing the unique features for these two switchingmechanisms, we realize a bi-directional in situ switching for a single molecular device. The secondcandidate we study is the furan oligomers. Through SMBJ experiment with a large temperaturewindow (78 K to 300 K). The unique planar structure would allow us to differentiate thetemperature independent conductance and temperature dependent conductance contribution.We also discover that the temperature dependence is not due to a hopping mechanism but athermally activated tunneling mechanism.

Download or read book Charge Transport in Single Molecule Junctions written by Claudia Benesch and published by . This book was released on 2008 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Handbook of Materials Modeling written by Sidney Yip and published by Springer Science & Business Media. This book was released on 2007-11-17 with total page 2903 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first reference of its kind in the rapidly emerging field of computational approachs to materials research, this is a compendium of perspective-providing and topical articles written to inform students and non-specialists of the current status and capabilities of modelling and simulation. From the standpoint of methodology, the development follows a multiscale approach with emphasis on electronic-structure, atomistic, and mesoscale methods, as well as mathematical analysis and rate processes. Basic models are treated across traditional disciplines, not only in the discussion of methods but also in chapters on crystal defects, microstructure, fluids, polymers and soft matter. Written by authors who are actively participating in the current development, this collection of 150 articles has the breadth and depth to be a major contributor toward defining the field of computational materials. In addition, there are 40 commentaries by highly respected researchers, presenting various views that should interest the future generations of the community. Subject Editors: Martin Bazant, MIT; Bruce Boghosian, Tufts University; Richard Catlow, Royal Institution; Long-Qing Chen, Pennsylvania State University; William Curtin, Brown University; Tomas Diaz de la Rubia, Lawrence Livermore National Laboratory; Nicolas Hadjiconstantinou, MIT; Mark F. Horstemeyer, Mississippi State University; Efthimios Kaxiras, Harvard University; L. Mahadevan, Harvard University; Dimitrios Maroudas, University of Massachusetts; Nicola Marzari, MIT; Horia Metiu, University of California Santa Barbara; Gregory C. Rutledge, MIT; David J. Srolovitz, Princeton University; Bernhardt L. Trout, MIT; Dieter Wolf, Argonne National Laboratory.

Download or read book Contact and Length Dependent Effects in Single molecule Electronics written by Thomas Hines and published by . This book was released on 2013 with total page 127 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding charge transport in single molecules covalently bonded to electrodes is a fundamental goal in the field of molecular electronics. In the past decade, it has become possible to measure charge transport on the single-molecule level using the STM break junction method. Measurements on the single-molecule level shed light on charge transport phenomena which would otherwise be obfuscated by ensemble measurements of groups of molecules. This thesis will discuss three projects carried out using STM break junction. In the first project, the transition between two different charge transport mechanisms is reported in a set of molecular wires. The shortest wires show highly length dependent and temperature invariant conductance behavior, whereas the longer wires show weakly length dependent and temperature dependent behavior. This trend is consistent with a model whereby conduction occurs by coherent tunneling in the shortest wires and by incoherent hopping in the longer wires. Measurements are supported with calculations and the evolution of the molecular junction during the pulling process is investigated. The second project reports controlling the formation of single-molecule junctions by means of electrochemically reducing two axial-diazonium terminal groups on a molecule, thereby producing direct Au-C covalent bonds in-situ between the molecule and gold electrodes. Step length analysis shows that the molecular junction is significantly more stable, and can be pulled over a longer distance than a comparable junction created with amine anchoring bonds. The stability of the junction is explained by the calculated lower binding energy associated with the direct Au-C bond compared with the Au-N bond. Finally, the third project investigates the role that molecular conformation plays in the conductance of oligothiophene single-molecule junctions. Ethyl substituted oligothiophenes were measured and found to exhibit temperature dependent conductance and transition voltage for molecules with between two and six repeat units. While the molecule with only one repeat unit shows temperature invariant behavior. Density functional theory calculations show that at higher temperatures the oligomers with multiple repeat units assume a more planar conformation, which increases the conjugation length and decreases the effective energy barrier of the junction.

Download or read book Theoretical Study of the Charge Transport Through C60 based Single molecule Junctions written by and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Charge carrier Transport Measurements Through Single Molecules written by Emanuel Marc Lörtscher and published by Cuvillier Verlag. This book was released on 2007 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Approach to Control Protect and Switch Charge Transport Through Molecular Junctions and Atomic Contact written by Yong Ai and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Molecular electronics has attracted increasing interest in the past decades. Constructing metal/molecules/metal junctions is a basic step towards the investigation of molecular electronics. We have witnessed significant development in both experiment and theory in molecular junctions. This thesis focuses mainly on the study of charge transport through molecular junctions. Conducting polymers and copper filaments were electrochemically deposited with a scanning electrochemical microscope (SECM) configuration between a tip and a substrate electrode. In doing so, we have developed a new way to fabricate atomic contact and molecular junctions, and we have explored the possibility to control, protect and switch these systems.Firstly, SECM, where two microelectrodes are located face-to-face separated by a micrometric gap, has been successfully used for the fabrication of redox-gated conducting polymers junctions, such as PEDOT and PBT. Highly stable and reversible redox-gated nano-junctions were obtained with conductance in the 10-7-10-8 S range in their conducting states. These results, associated with the wire-like growth of the polymer, suggest that the conductance of the entire junction in the conductive state is governed by less than 20 to 100 oligomers.Secondly, to obtain the nano-junctions in a controllable way, a break junction strategy combined with the SECM set up is adopted. A nano-junction could be acquired by pulling the tip away from its initial position. And conductance traces showed that PEDOT junctions can be broken step by step before complete breakdown. Similarly as STM-BJ conductance steps were observed on a PEDOT molecular junction before break down by using SECM-BJ. SECM break junction technique proved to be an efficient way of molecular junction fabrication studies, especially for redox gated polymer molecular junctions. Moreover, a self-terminated strategy is found to be another way to obtain nano-junctions. An external resistance connected to the electrode plays an important role in controlling the size of conducting polymer junctions.PFTQ and PFETQ molecular junctions exhibit well-defined ambipolar transport properties. However, an unbalanced charge transport properties in n- and p- channel for these two polymer junctions was observed when the junctions are in the fiber device scale. In contrast, when molecular junction changes into nano-junction, a balanced n- and p-channel transport property is acquired. We propose that such effect is due to charge transport mechanism changing from diffusive (ohm's law) to ballistic (quantum theory) when the junction size is reduced from fiber devices to nanodevices.High stable Au NPs/ITO electrodes exhibit a well localized surface plasmon (LSP) behavior. These plasmonic substrates have been successfully used to trigger switching of molecular junctions under light irradiation, demonstrating that surface plasmon resonance can induce electrochemical reduction. Such conductance reduction can be attributed to the hot electrons plasmonically generated from gold nanoparticles trapped into the PEDOT junction, resulting in PEDOT being reduced and changed to an insulating state.Finally, copper metallic nanowires were generated using an electrochemical self-terminated method based on SECM configuration. The presence of a few atoms that control the electron transport highlights the formation of metallic nanowires between the asymmetric electrodes. Furthermore, a similar study was performed on mesoporous silica film on ITO used as a substrate electrode. The mesoporous silica films have vertically aligned channels with a diameter of about 3 nm and a thickness of 115 nm, which play a crucial role in protecting the copper filament.

Download or read book Functional Materials Processing for Switchable Device Modulation written by Kaushik Pal and published by Woodhead Publishing. This book was released on 2021-10-19 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt: Functional Materials Processing for Switchable Device Modulation focuses on the advances of nanofabrication that underpin emerging technologies, including electronic devices. The book provides readers with a broad view of the materials’ perspectives, including historical context and background, along with future opportunities for smart electronic and switchable devices. A major focus in the book is on the research and development of synthetic materials for spectroscopic analysis which broadly deals with science and technology of materials on the atomic and molecular scale. The book reviews the materials and advances in research for switchable electronics for bioelectronic, sensing and optoelectronic applications. In addition, key challenges and emerging opportunities in innovations in surface modification and novel functional materials device implementation for industrial scale reproducibility are discussed. The book covers the applications and market potential for a variety of media, including mirrors, glazing/coatings, and display products. The physics, electrochemistry, device design and materials are detailed, with performance compared between the most relevant and emerging switchable technologies. Addresses the most interesting advances in switchable devices for bioelectronics, electronics, optoelectronics and sensing applications Includes a special emphasis on materials design, processing and fabrication of switchable devices to realize large-scale industry applications Compares the performance of existing innovative switchable devices Reviews the remaining barriers to commercialization, along with opportunities to address these challenges

Download or read book Nanogap Electrodes written by Tao Li and published by John Wiley & Sons. This book was released on 2021-08-16 with total page 434 pages. Available in PDF, EPUB and Kindle. Book excerpt: Unique in its scope, this book comprehensively combines various synthesis strategies with applications for nanogap electrodes. Clearly divided into four parts, the monograph begins with an introduction to molecular electronics and electron transport in molecular junctions, before moving on to a whole section devoted to synthesis and characterization. The third part looks at applications with single molecules or self-assembled monolayers, and the whole is rounded off with a section on interesting phenomena observed using molecular-based devices.

Download or read book Vibrationally Coupled Charge Transport in Single molecule Junctions written by Christoph Kaspar and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Theory of Charge Transport Through Vibrating Molecules written by Yelena Simine and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Electromechanical Properties of Single Molecule Devices written by Christopher Bruot and published by . This book was released on 2014 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding the interplay between the electrical and mechanical properties of single molecules is of fundamental importance for molecular electronics. The sensitivity of charge transport to mechanical fluctuations is a key problem in developing long lasting molecular devices. Furthermore, harnessing this response to mechanical perturbation, molecular devices which can be mechanically gated can be developed. This thesis demonstrates three examples of the unique electromechanical properties of single molecules. First, the electromechanical properties of 1,4-benzenedithiol molecular junctions are investigate. Counterintuitively, the conductance of this molecule is found to increase by more than an order of magnitude when stretched. This conductance increase is found to be reversible when the molecular junction is compressed. The current-voltage, conductance-voltage and inelastic electron tunneling spectroscopy characteristics are used to attribute the conductance increase to a strain-induced shift in the frontier molecular orbital relative to the electrode Fermi level, leading to resonant enhancement in the conductance. Next, the effect of stretching-induced structural changes on charge transport in DNA molecules is studied. The conductance of single DNA molecules with lengths varying from 6 to 26 base pairs is measured and found to follow a hopping transport mechanism. The conductance of DNA molecules is highly sensitive to mechanical stretching, showing an abrupt decrease in conductance at surprisingly short stretching distances, with weak dependence on DNA length. This abrupt conductance decrease is attributed to force-induced breaking of hydrogen bonds in the base pairs at the end of the DNA sequence. Finally, the effect of small mechanical modulation of the base separation on DNA conductance is investigated. The sensitivity of conductance to mechanical modulation is studied for molecules of different sequence and length. Sequences with purine-purine stacking are found to be more responsive to modulation than purine-pyrimidine sequences. This sensitivity is attributed to the perturbation of pi-pi stacking interactions and resulting effects on the activation energy and electronic coupling for the end base pairs.

Download or read book Charge Transport in Single molecule Junctions with Fullerene End groups written by Benjamin Gmeiner and published by . This book was released on 2010 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Charge Transport Through Single Molecules in Two and Three terminal Mechanical Break Junctions written by Christian Alexander Martin and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: