The Experts below are selected from a list of 195 Experts worldwide ranked by ideXlab platform
Manabu Kiguchi - One of the best experts on this subject based on the ideXlab platform.
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Fabrication and Conductance characterization of single C60 molecular junction in solutions
Chemical Physics Letters, 2020Co-Authors: Manabu Kiguchi, Jianwei Zhao, Kei MurakoshiAbstract:The Conductance and stretching length of the single C60 molecule bridging two Au electrodes (C60 molecular junction) were studied in air, mesitylene and 0.1 M HClO4 solution. In air, the C60 molecular junction did not show any well-defined Conductance Value. In either mesitylene or HClO4 solution, the systems showed a Conductance Value of 0.01 G0. The stretching length of the single C60 molecular junction was determined to be 0.01 nm. The Values of the Conductance and stretching length in solution were smaller than those obtained in ultra high vacuum, indicating the weak C60-Au interaction in solution. Considering the particular shape of the C60 molecule and the junction formation process in the present system, a sliding model was proposed to interpret the observation
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Investigation on the Pyrazine Molecular Junction Studied by Conductance Measurement and Near Edge X-ray Absorption Fine Structure
Fullerenes Nanotubes and Carbon Nanostructures, 2014Co-Authors: Satoshi Kaneko, Manabu KiguchiAbstract:A pyrazine molecular junction was investigated using mechanically controllable break junction (MCBJ) technique at 10 K. The Conductance measurements revealed the single pyrazine molecular junctions showed two distinct Conductance Values of 0.27 ± 0.04 and 1.0 ± 0.2 G 0 (2e 2/h). The Conductance Value of the single pyrazine molecular junction was comparable with that of the metal atomic junction. The interface between pyrazine molecule and Pt surface was investigated by near edge X-ray absorption fine structure (NEXAFS). The broadening of the π* peak in N K-edge NEXAFS spectra suggested that the pyrazine molecule connected to Pt surface via a nitrogen atom. Based on the measurements of the Conductance and NEXAFS, we could propose the structural models of two distinct Conductance states for the single pyrazine molecular junction.
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Effect of the environment on the electrical Conductance of the single benzene-1,4-diamine molecule junction.
Beilstein Journal of Nanotechnology, 2011Co-Authors: Shigeto Nakashima, Yuuta Takahashi, Manabu KiguchiAbstract:We investigated the effect of the environment on the electrical Conductance of a single benzene-1,4-diamine (BDA) molecule bridging Au electrodes, using the scanning tunneling microscope (STM). The Conductance of the single BDA molecule junction decreased upon a change in the environment from tetraglyme, to mesitylene, to water, and finally to N2 gas, while the spread in the Conductance Value increased. The order of the Conductance Values of the single BDA molecule junction was explained by the strength of the interaction between the solvent molecules and the Au electrodes. The order of the spread in the Conductance Values was explained by the diversity in the coverage of the BDA molecule at metal electrodes and atomic and molecular motion of the single-molecule junction.
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Fabrication of a Well-Defined Single Benzene Molecule Junction Using Ag Electrodes
Journal of Physical Chemistry Letters, 2010Co-Authors: Satoshi Kaneko, Tomoka Nakazumi, Manabu KiguchiAbstract:The formation of the single benzene molecule junction was investigated for Au and Ag electrodes by Conductance measurements and inelastic tunneling electron spectroscopy at 10 K. While a single benzene molecule junction was hardly formed for the Au electrodes, a single benzene molecule junction was formed for the Ag electrodes. The single Ag/benzene/Ag junction showed a fixed Conductance Value of 0.24 G0 (G0 = 2e2/h), indicating the formation of a well-defined single benzene molecule junction. By comparing with previously reported results for Pt electrodes, in which the single benzene molecule junction showed various Conductance Values, it was shown that the moderate metal−molecule interaction is favorable to obtain a well-defined single molecule junction.
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Electrical Conductance of Rh atomic contacts under electrochemical potential control
Physical Review B, 2010Co-Authors: Tatsuya Konishi, Manabu Kiguchi, Kei MurakoshiAbstract:The electric Conductance of Rh atomic contacts was investigated under the electrochemical potential control. The Conductance histogram of Rh atomic contacts varied with the electrochemical potential. When the electrochemical potential of the contact was kept at $\Phi_{0}$= 0.1 V vs. Ag/AgCl (Rh potential), the Conductance histogram did not show any features. At $\Phi_{0}$= -0.1 V (under potential deposited hydrogen potential), the Conductance histogram showed a feature around 2.3 $G_{0}$ ($G_{0}$ =2$e^{2}/h$), which agreed with the Conductance Value of a clean Rh atomic contact, which was observed in ultrahigh vacuum at low temperature. At $\Phi_{0}$= -0.25 V (over potential deposited hydrogen potential), the Conductance histogram showed features around 0.3 and 1.0 $G_{0}$. The Conductance behavior of the Rh atomic contact was discussed by comparing previously reported results of other metals, Au, Ag, Cu, Pt, Pd, Ni, Co, and Fe. The Conductance behavior of the metal atomic contacts related with the strength of the interaction between hydrogen and metal surface.
Satoshi Kaneko - One of the best experts on this subject based on the ideXlab platform.
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Anchoring Groups Enclosed in the π-Conjugated System in N 2 Molecules
Design and Control of Highly Conductive Single-Molecule Junctions, 2017Co-Authors: Satoshi KanekoAbstract:In the previous chapter, single-molecule junctions with a high, well-defined Conductance Value were fabricated by designing the interaction between molecule and metal and spherical structure. In order to control the electrical properties of the single-molecule junction, it is important to control their interface structure. The anchoring groups enclosed in π-conjugated systems are expected to fix the connecting points with high conductivity. Here, N2 is discussed as the simplest π-conjugated system with anchoring points. The MCBJ technique combined with theoretical calculations reveals the basic properties of the π-conjugated system with anchoring points: formation and Conductance Value of the singe-molecule junction.
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Design of the Metal–Molecule Interaction at the Benzene Single-Molecule Junction
Design and Control of Highly Conductive Single-Molecule Junctions, 2017Co-Authors: Satoshi KanekoAbstract:In this chapter, the influence of the strength of the metal–molecule interaction on the formation of a single-molecule junction with a high, well-defined Conductance Value was investigated. Although the Pt/benzene/Pt single-molecule junction exhibits high conductivity, its Conductance Value is not well defined. In order to restrict the configuration of the benzene molecule, the strength of the interaction between the metal and benzene should be reduced. Ag and Au are expected to interact more gently with the benzene than Pt. The moderately strong interaction between Ag and benzene successfully formed a single-molecule junction; however, Au did not form a single-molecule junction because of the formation of the linear atomic chain.
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Investigation on the Pyrazine Molecular Junction Studied by Conductance Measurement and Near Edge X-ray Absorption Fine Structure
Fullerenes Nanotubes and Carbon Nanostructures, 2014Co-Authors: Satoshi Kaneko, Manabu KiguchiAbstract:A pyrazine molecular junction was investigated using mechanically controllable break junction (MCBJ) technique at 10 K. The Conductance measurements revealed the single pyrazine molecular junctions showed two distinct Conductance Values of 0.27 ± 0.04 and 1.0 ± 0.2 G 0 (2e 2/h). The Conductance Value of the single pyrazine molecular junction was comparable with that of the metal atomic junction. The interface between pyrazine molecule and Pt surface was investigated by near edge X-ray absorption fine structure (NEXAFS). The broadening of the π* peak in N K-edge NEXAFS spectra suggested that the pyrazine molecule connected to Pt surface via a nitrogen atom. Based on the measurements of the Conductance and NEXAFS, we could propose the structural models of two distinct Conductance states for the single pyrazine molecular junction.
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Fabrication of a Well-Defined Single Benzene Molecule Junction Using Ag Electrodes
Journal of Physical Chemistry Letters, 2010Co-Authors: Satoshi Kaneko, Tomoka Nakazumi, Manabu KiguchiAbstract:The formation of the single benzene molecule junction was investigated for Au and Ag electrodes by Conductance measurements and inelastic tunneling electron spectroscopy at 10 K. While a single benzene molecule junction was hardly formed for the Au electrodes, a single benzene molecule junction was formed for the Ag electrodes. The single Ag/benzene/Ag junction showed a fixed Conductance Value of 0.24 G0 (G0 = 2e2/h), indicating the formation of a well-defined single benzene molecule junction. By comparing with previously reported results for Pt electrodes, in which the single benzene molecule junction showed various Conductance Values, it was shown that the moderate metal−molecule interaction is favorable to obtain a well-defined single molecule junction.
Rukkiat Jitchati - One of the best experts on this subject based on the ideXlab platform.
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Electrical Conductance of conjugated oligomers at the single molecule level
Journal of the American Chemical Society, 2008Co-Authors: Roman Huber, Matías Mayor, Songmei Wu, Michael Langer, Viviana Horhoiu, Sergio Grunder, Martin Robert Bryce, María Teresa González, Changsheng Wang, Rukkiat JitchatiAbstract:We determine and compare, at the single molecule level and under identical environmental conditions, the electrical Conductance of four conjugated phenylene oligomers comprising terminal sulfur anchor groups with simple structural and conjugation variations. The comparison shows that the Conductance of oligo(phenylene vinylene) (OPV) is slightly higher than that of oligo(phenylene ethynylene) (OPE). We find that solubilizing side groups do neither prevent the molecules from being anchored within a break junction nor noticeably influence the Conductance Value.
Daniele Ielmini - One of the best experts on this subject based on the ideXlab platform.
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In-Memory PageRank Accelerator With a Cross-Point Array of Resistive Memories
IEEE Transactions on Electron Devices, 2020Co-Authors: Elia Ambrosi, Giacomo Pedretti, Alessandro Bricalli, Daniele IelminiAbstract:In-memory computing with cross-point arrays of resistive memory is a promising technique for typical tasks, such as the training and inference of deep learning. Recently, it has been shown that a cross-point array of resistive switching memory (RRAM) with a feedback configuration can be used to solve linear systems, compute eigenvectors, and rank webpages in just one step. Here, we demonstrate the PageRank with a real data set (the Harvard500) and an eight-level RRAM model, describing the Conductance update, the standard deviation of each level, and the Conductance ratio. By carefully placing each memory Conductance Value via a program-verify technique, we show that an accuracy of 95% can be achieved for the ranking result. The equivalent throughput of the eigenvector circuit for PageRank is estimated to be 0.183 tera-operations per second (TOPS), while the energy efficiency is 362 TOPS/W. This article supports the feasibility of in-memory PageRank with significant improvements in speed and energy efficiency for practical big-data tasks.
Geoffrey W. Burr - One of the best experts on this subject based on the ideXlab platform.
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Bidirectional Non-Filamentary RRAM as an Analog Neuromorphic Synapse, Part II: Impact of Al/Mo/Pr0.7Ca0.3MnO3 Device Characteristics on Neural Network Training Accuracy
IEEE Journal of the Electron Devices Society, 2018Co-Authors: Alessandro Fumarola, Severin Sidler, Robert M. Shelby, Pritish Narayanan, Junwoo Jang, Kibong Moon, Yusuf Leblebici, Hyunsang Hwang, Geoffrey W. BurrAbstract:Neuromorphic computing embraces the “device history” offered by many analog non-volatile memory (NVM) devices to implement the small weight changes computed by a gradient-descent learning algorithm such as backpropagation. Deterministic and stochastic imperfections in the Conductance response of real NVM devices can be encapsulated for modeling within a pair of “jump-tables.” Such jump-tables describe the full cumulative distribution function of Conductance-change at each device Conductance Value, for both weight potentiation (SET) and depression (RESET). First, using several types of artificially constructed jump-tables, we revisit the relative importance of deviations from an ideal NVM with perfectly linear Conductance response. Then, using jump-tables measured on improved non-filamentary resistive RAM devices based on Pr0.7Ca0.3MnO3[see companion paper], we simulate the effects of their nonlinear Conductance response on the training of a three-layer fully connected neural network. We find that, despite the relatively large Conductance changes exhibited by any Pr0.7Ca0.3MnO3device when either potentiating from its lowest Conductance state or depressing from its highest Conductance states, neural network training accuracies of >90% can be achieved. Highest accuracies are achieved by programming both Conductances on each timestep (“fully bidirectional”), with the improved Conductance on/off ratio of Al/Mo/PCMO resulting in marked improvements in training and test accuracy. Further accuracy improvements can be obtained by tuning the relative learning rate for potentiation (SET) by a factor of 1.66× with respect to depression (RESET), to offset the slight asymmetry between the average size of the associated SET and RESET Conductance changes. Finally, we show that the bidirectional programming of Al/Mo/PCMO can be used to implement high-density neuromorphic systems with a single Conductance per synapse, at only a slight degradation to accuracy.
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Large-scale neural networks implemented with Non-Volatile Memory as the synaptic weight element: Impact of Conductance response
2016 46th European Solid-State Device Research Conference (ESSDERC), 2016Co-Authors: Severin Sidler, Irem Boybat, Robert M. Shelby, Pritish Narayanan, Junwoo Jang, Alessandro Fumarola, Kibong Moon, Yusuf Leblebici, Hyunsang Hwang, Geoffrey W. BurrAbstract:We assess the impact of the Conductance response of Non-Volatile Memory (NVM) devices employed as the synaptic weight element for on-chip acceleration of the training of large-scale artificial neural networks (ANN). We briefly review our previous work towards achieving competitive performance (classification accuracies) for such ANN with both Phase-Change Memory (PCM) [1], [2] and non-filamentary ReRAM based on PrCaMnO (PCMO) [3], and towards assessing the potential advantages for ML training over GPU-based hardware in terms of speed (up to 25× faster) and power (from 120-2850× lower power) [4]. We then discuss the “jump-table” concept, previously introduced to model real-world NVM such as PCM [1] or PCMO, to describe the full cumulative distribution function (CDF) of Conductance-change at each device Conductance Value, for both potentiation (SET) and depression (RESET). Using several types of artificially-constructed jump-tables, we assess the relative importance of deviations from an ideal NVM with perfectly linear Conductance response.