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Christian Joachim - One of the best experts on this subject based on the ideXlab platform.
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Quantum Hamiltonian Computing protocols for Molecular Electronics Boolean logic gates
arXiv: Quantum Physics, 2019Co-Authors: Omid Faizy Namarvar, Olivier Giraud, Bertrand Georgeot, Christian JoachimAbstract:Quantum Hamiltonian Computing is a recent approach that uses quantum systems, in particular a single molecule, to perform computational tasks. Within this approach, we present explicit methods to construct logic gates using two different designs, where the logical outputs are encoded either at fixed energy and spatial positioning of the quantum states, or at different energies. We use these results to construct quantum Boolean adders involving a minimal number of quantum states with the two designs. We also establish a matrix algebra giving an analogy between classical Boolean logic gates and quantum ones, and assess the possibilities of both designs for more complex gates.
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Molecular Electronics
Proceedings of the National Academy of Sciences of the United States of America, 2005Co-Authors: Christian Joachim, Mark A RatnerAbstract:Current work in Molecular Electronics usually addresses Molecular junction electronic transport properties, where the molecule can be viewed as a barrier for incoming electrons. This is the fundamental Landauer idea of “conduction as scattering” generalized to metal/single molecule/metal Molecular nanojunction structures. The experimental contributions from the Gourdon and Hersam groups focus on the tunneling process in Molecular transport junctions, using powerful and elegant techniques involving both demanding single-molecule junction synthesis and scanning tunneling microscopy and spectroscopy. The paper by Ho's group extends these experimental methods to examine vibronic components in the STM-geometry conductance, using precisely engineered surface structures. The contribution by Fisher and Ness addresses those inelastic effects in junction transport from a theoretical point of view. The papers from the Mayor and Kushmerick groups address such transport issues as fluctuation and vibronic features of Molecular electronic wires by using break-junction and monolayer test beds.
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Molecular Electronics some views on transport junctions and beyond
Proceedings of the National Academy of Sciences of the United States of America, 2005Co-Authors: Christian Joachim, Mark A RatnerAbstract:The field of Molecular Electronics comprises a fundamental set of issues concerning the electronic response of molecules as parts of a mesoscopic structure and a technology-facing area of science. We will overview some important aspects of these subfields. The most advanced ideas in the field involve the use of molecules as individual logic or memory units and are broadly based on using the quantum state space of the molecule. Current work in Molecular Electronics usually addresses Molecular junction transport, where the molecule acts as a barrier for incoming electrons: This is the fundamental Landauer idea of “conduction as scattering” generalized to Molecular junction structures. Another point of view in terms of superexchange as a guiding mechanism for coherent electron transfer through the Molecular bridge is discussed. Molecules generally exhibit relatively strong vibronic coupling. The last section of this overview focuses on vibronic effects, including inelastic electron tunneling spectroscopy, hysteresis in junction charge transport, and negative differential resistance in Molecular transport junctions.
Mark A Ratner - One of the best experts on this subject based on the ideXlab platform.
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towards graphyne Molecular Electronics
Nature Communications, 2015Co-Authors: Manuel Smeu, Mark A Ratner, Arnaud Rives, Valerie Maraval, Remi Chauvin, Eric BorguetAbstract:α-Graphyne, a carbon-expanded version of graphene (‘carbo-graphene’) that was recently evidenced as an alternative zero-gap semiconductor, remains a theoretical material. Nevertheless, using specific synthesis methods, Molecular units of α-graphyne (‘carbo-benzene’ macrocycles) can be inserted between two anilinyl (4-NH2-C6H4)-anchoring groups that allow these fragments to form Molecular junctions between gold electrodes. Here, electrical measurements by the scanning tunnelling microscopy (STM) break junction technique and electron transport calculations are carried out on such a carbo-benzene, providing unprecedented single molecule conductance values: 106 nS through a 1.94-nm N–N distance, essentially 10 times the conductance of a shorter nanographenic hexabenzocoronene analogue. Deleting a C4 edge of the rigid C18 carbo-benzene circuit results in a flexible ‘carbo-butadiene’ molecule that has a conductance 40 times lower. Furthermore, carbo-benzene junctions exhibit field-effect transistor behaviour when an electrochemical gate potential is applied, opening the way for device applications. All the results are interpreted on the basis of theoretical calculations. α-Graphyne, a carbon-expanded version of graphene, is predicted to exhibit high conductivity due to its Dirac cone electronic structure. Here, Li et al.design and synthesize a series of Molecular fragments of α-graphyne, on the basis of which single Molecular junctions are realized.
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forty years of Molecular Electronics non equilibrium heat and charge transport at the nanoscale
Physica Status Solidi B-basic Solid State Physics, 2013Co-Authors: Justin P Bergfield, Mark A RatnerAbstract:The “Quo Vadis?” meeting in Bremen (March 2013) was a spectacular opportunity for people involved in Molecular Electronics to catch up on the latest, to think back, and to project into the future. This manuscript is divided into two halves. In the first half, we address some of the history and where the field has advanced in the areas of measuring, modeling, making, and understanding materials. We review some big ideas that have animated the field of Molecular Electronics since its beginning, and are at the height of interest and accomplishment at the moment. Then, we discuss six major areas where the field is evolving, and in which we expect to see very exciting work in the years and decades ahead. As a representative of one of the neer themes, the second half of the paper is devoted to Molecular thermoelectrics. It contains some formalism, some results, some experimental comparison, and some intriguing conceptual questions, both for pure science and for device applications. An artist's rendition of a self-assembled monolayer of polyphenylether molecules on Au contacted by a Au STM.
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Molecular Electronics
Proceedings of the National Academy of Sciences of the United States of America, 2005Co-Authors: Christian Joachim, Mark A RatnerAbstract:Current work in Molecular Electronics usually addresses Molecular junction electronic transport properties, where the molecule can be viewed as a barrier for incoming electrons. This is the fundamental Landauer idea of “conduction as scattering” generalized to metal/single molecule/metal Molecular nanojunction structures. The experimental contributions from the Gourdon and Hersam groups focus on the tunneling process in Molecular transport junctions, using powerful and elegant techniques involving both demanding single-molecule junction synthesis and scanning tunneling microscopy and spectroscopy. The paper by Ho's group extends these experimental methods to examine vibronic components in the STM-geometry conductance, using precisely engineered surface structures. The contribution by Fisher and Ness addresses those inelastic effects in junction transport from a theoretical point of view. The papers from the Mayor and Kushmerick groups address such transport issues as fluctuation and vibronic features of Molecular electronic wires by using break-junction and monolayer test beds.
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Molecular Electronics some views on transport junctions and beyond
Proceedings of the National Academy of Sciences of the United States of America, 2005Co-Authors: Christian Joachim, Mark A RatnerAbstract:The field of Molecular Electronics comprises a fundamental set of issues concerning the electronic response of molecules as parts of a mesoscopic structure and a technology-facing area of science. We will overview some important aspects of these subfields. The most advanced ideas in the field involve the use of molecules as individual logic or memory units and are broadly based on using the quantum state space of the molecule. Current work in Molecular Electronics usually addresses Molecular junction transport, where the molecule acts as a barrier for incoming electrons: This is the fundamental Landauer idea of “conduction as scattering” generalized to Molecular junction structures. Another point of view in terms of superexchange as a guiding mechanism for coherent electron transfer through the Molecular bridge is discussed. Molecules generally exhibit relatively strong vibronic coupling. The last section of this overview focuses on vibronic effects, including inelastic electron tunneling spectroscopy, hysteresis in junction charge transport, and negative differential resistance in Molecular transport junctions.
Supriyo Datta - One of the best experts on this subject based on the ideXlab platform.
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silicon based Molecular Electronics
Nano Letters, 2004Co-Authors: Titash Rakshit, Gengchiau Liang, Avik W Ghosh, Supriyo DattaAbstract:Molecular Electronics on silicon has distinct advantages over its metallic counterpart. We describe a theoretical formalism for transport in semiconductor−molecule heterostructures, formally combining a semiempirical treatment of bulk silicon with a first-principles description of the Molecular chemistry and its bonding with silicon. Using this method, we demonstrate that the presence of a semiconducting band-edge can lead to a novel Molecular resonant tunneling diode (RTD) that shows negative differential resistance (NDR) when the Molecular levels are driven by an STM potential into the semiconducting band gap. The NDR peaks show a clear polarity reversal, appearing for positive bias on a p-doped and negative for an n-doped substrate, a feature that is in agreement with recent experiments by Guisinger et al.1,2
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thermoelectric effect in Molecular Electronics
Physical Review B, 2003Co-Authors: Magnus Paulsson, Supriyo DattaAbstract:We provide a theoretical estimate of the thermoelectric current and voltage over a Phenyldithiol molecule. We also show that the thermoelectric voltage is (1) easy to analyze, (2) insensitive to the detailed coupling to the contacts, (3) large enough to be measured, and (4) give valuable information, which is not readily accessible through other experiments, on the location of the Fermi energy relative to the Molecular levels. The location of the Fermi-energy is poorly understood and controversial even though it is a central factor in determining the nature of conduction $(n$ or p type). We also note that the thermoelectric voltage measured over Guanine molecules with a scanning tunneling microscope by Poler et al., indicate conduction through the highest occupied Molecular orbital level, i.e., p-type conduction.
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silicon based Molecular Electronics
arXiv: Mesoscale and Nanoscale Physics, 2003Co-Authors: Titash Rakshit, Gengchiau Liang, Avik W Ghosh, Supriyo DattaAbstract:Molecular Electronics on silicon has distinct advantages over its metallic counterpart. We describe a theoretical formalism for transport through semiconductor-molecule heterostructures, combining a semi-empirical treatment of the bulk silicon bandstructure with a first-principles description of the Molecular chemistry and its bonding with silicon. Using this method, we demonstrate that the presence of a semiconducting band-edge can lead to a novel Molecular resonant tunneling diode (RTD) that shows negative differential resistance (NDR) when the Molecular levels are driven by an STM potential into the semiconducting band-gap. The peaks appear for positive bias on a p-doped and negative for an n-doped substrate. Charging in these devices is compromised by the RTD action, allowing possible identification of several Molecular highest occupied (HOMO) and lowest unoccupied (LUMO) levels. Recent experiments by Hersam et al. [1] support our theoretical predictions.
David Cahen - One of the best experts on this subject based on the ideXlab platform.
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chemical modification of semiconductor surfaces for Molecular Electronics
Chemical Reviews, 2017Co-Authors: Ayelet Vilan, David CahenAbstract:Inserting Molecular monolayers within metal/semiconductor interfaces provides one of the most powerful expressions of how minute chemical modifications can affect electronic devices. This topic also has direct importance for technology as it can help improve the efficiency of a variety of electronic devices such as solar cells, LEDs, sensors, and possible future bioelectronic ones. The review covers the main aspects of using chemistry to control the various aspects of interface electrostatics, such as passivation of interface states and alignment of energy levels by intrinsic Molecular polarization, as well as charge rearrangement with the adjacent metal and semiconducting contacts. One of the greatest merits of Molecular monolayers is their capability to form excellent thin dielectrics, yielding rich and unique current–voltage characteristics for transport across metal/Molecular monolayer/semiconductor interfaces. We explain the interplay between the monolayer as tunneling barrier on the one hand, and th...
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large area ensemble Molecular Electronics motivation and challenges
Chemical Reviews, 2017Co-Authors: Ayelet Vilan, D K Aswal, David CahenAbstract:We review charge transport across Molecular monolayers, which is central to Molecular Electronics (MolEl), using large-area junctions (NmJ). We strive to provide a wide conceptual overview of three main subtopics. First, a broad introduction places NmJ in perspective to related fields of research and to single-molecule junctions (1mJ) in addition to a brief historical account. As charge transport presents an ultrasensitive probe for the electronic perfection of interfaces, in the second part ways to form both the monolayer and the contacts are described to construct reliable, defect-free interfaces. The last part is dedicated to understanding and analyses of current–voltage (I–V) traces across Molecular junctions. Notwithstanding the original motivation of MolEl, I–V traces are often not very sensitive to Molecular details and then provide a poor probe for chemical information. Instead, we focus on how to analyze the net electrical performance of Molecular junctions, from a functional device perspective. ...
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large area ensemble Molecular Electronics motivation and challenges
arXiv: Materials Science, 2016Co-Authors: Ayelet Vilan, D K Aswal, David CahenAbstract:We review charge transport across Molecular monolayers, which is central to Molecular Electronics (MoE) using large-area junctions (NmJ). We strive to provide a wide conceptual overview of three main sub-topics. First, a broad introduction places NmJ in perspective to related fields of research, and to single molecule junctions (1mJ), in addition to a brief historical account. As charge transport presents an ultra sensitive probe for the electronic perfection of interfaces, in the second part ways to form both the monolayer and the contacts are described to construct reliable, defect-free interfaces. The last part is dedicated to understanding and analyses of current-voltage (I-V) traces across Molecular junctions. Notwithstanding the original motivation of MoE, I-V traces are often not very sensitive to Molecular details and then provide a poor probe for chemical information. Instead we focus on how to analyse the net electrical performance of Molecular junctions, from a functional device perspective. Finally, we shortly point to creation of a built-in electric field as a key to achieve functionality, including non-linear current-voltage characteristics that originate in the molecules or their contacts to the electrodes.
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Molecular Electronics by chemical modification of semiconductor surfaces
arXiv: Materials Science, 2016Co-Authors: Ayelet Vilan, David CahenAbstract:Inserting Molecular monolayers within metal / semiconductor interfaces provides one of the most powerful expressions of how minute chemical modifications can affect electronic devices. This topic also has direct importance for technology as it can help improve the efficiency of a variety of electronic devices such as solar cells, LEDs, sensors and possible future bioelectronic devices, which are based mostly on non-classical semiconducting materials (section 1). The review covers the main aspects of using chemistry to - control alignment of energy levels at interfaces (section 2): - passivate interface states (section 3), - insert Molecular dipoles at interfaces (section 4), - induce charge rearrangement at and around interfaces (section 5). After setting the stage, we consider the unique current-voltage characteristics that result from transport across metal / Molecular monolayer / semiconductor interfaces. Here we focus on the interplay between the monolayer as tunneling barrier on the one hand, and the electrostatic barrier within the semiconductor, due to its space-charge region (section 6), on the other hand, as well as how different monolayer chemistries control each of the these barriers. Section 7 provides practical tools to experimentally identify these two barriers, and distinguish between them, after which section 8 concludes the story with a summary and a view to the future. While this review is concerned with hybrid semiconductor / Molecular effects (see Refs. 1,2 for earlier reviews on this topic), issues related to formation of monolayers and contacts, as well as charge transport that is solely dominated by molecules, have been reviewed elsewhere[3-6], including by us recently[7].
Colin Nuckolls - One of the best experts on this subject based on the ideXlab platform.
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silane and germane Molecular Electronics
Accounts of Chemical Research, 2017Co-Authors: Rebekka S Klausen, Nathaniel T Kim, Madhav Neupane, James L Leighton, Michael L Steigerwald, Latha Venkataraman, Colin NuckollsAbstract:ConspectusThis Account provides an overview of our recent efforts to uncover the fundamental charge transport properties of Si–Si and Ge–Ge single bonds and introduce useful functions into group 14 Molecular wires. We utilize the tools of chemical synthesis and a scanning tunneling microscopy-based break-junction technique to study the mechanism of charge transport in these Molecular systems. We evaluated the fundamental ability of silicon, germanium, and carbon Molecular wires to transport charge by comparing conductances within families of well-defined structures, the members of which differ only in the number of Si (or Ge or C) atoms in the wire. For each family, this procedure yielded a length-dependent conductance decay parameter, β. Comparison of the different β values demonstrates that Si–Si and Ge–Ge σ bonds are more conductive than the analogous C–C σ bonds. These Molecular trends mirror what is seen in the bulk.The conductance decay of Si and Ge-based wires is similar in magnitude to those from ...
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helical ribbons for Molecular Electronics
Journal of the American Chemical Society, 2014Co-Authors: Yu Zhong, Michael L Steigerwald, Colin Nuckolls, Bharat Kumar, Tuan M Trinh, Katherine C Elbert, X Y Zhu, Shengxiong XiaoAbstract:We describe the design and synthesis of a new graphene ribbon architecture that consists of perylenediimide (PDI) subunits fused together by ethylene bridges. We created a prototype series of oligomers consisting of the dimer, trimer, and tetramer. The steric congestion at the fusion point between the PDI units creates helical junctions, and longer oligomers form helical ribbons. Thin films of these oligomers form the active layer in n-type field effect transistors. UV–vis spectroscopy reveals the emergence of an intense long-wavelength transition in the tetramer. From DFT calculations, we find that the HOMO–2 to LUMO transition is isoenergetic with the HOMO to LUMO transition in the tetramer. We probe these transitions directly using femtosecond transient absorption spectroscopy. The HOMO–2 to LUMO transition electronically connects the PDI subunits with the ethylene bridges, and its energy depends on the length of the oligomer.
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cruciform π systems for Molecular Electronics applications
Journal of the American Chemical Society, 2003Co-Authors: Jennifer E Klare, George S Tulevski, Kenji Sugo, Anat De Picciotto, Kiley A White, Colin NuckollsAbstract:This study details a modular and general synthesis of a new class of molecules consisting of cruciform π-systems. The key to synthesizing these molecules was an unprecedented double Staudinger cycl...
