152 research outputs found

    Fabrication of stable Pd nanowire assisted by hydrogen in solution

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    We have mechanically fabricated a Pd nanowire in solution under electrochemical potential control. A clear feature appeared in the conductance histogram when the electrochemical potential of the Pd wire was kept at the hydrogen evolution potential. Conductance traces showed the Pd wire was stretched 0.4 nm in length just before breaking, suggesting that at least two Pd atoms might contribute to the formation of the Pd wire. The results indicate that a certain atomic configuration of the Pd nanowire is stabilized by hydrogen. We discuss the stabilization mechanism due to changes in bond strengths caused by hydrogen adsorption or incorporation.Comment: 4 pages, 3 figures, Appl. Phys. Lett., in pres

    Atomic Motion in Single H2_{2} and D2_{2} Molecule Junction Induced by Phonon Excitation

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    We have investigated Au atomic contacts in H2_{2} and D2_{2} environment by conductance measurement and dI/dVdI/dV spectroscopy. A single H2_{2} or D2_{2} molecule was found to bridge Au electrodes. In the case of the Au/H2_{2}/Au junction, symmetric peaks were observed in dI/dVdI/dV spectra, while they were not observed for the Au/D2_{2}/Au junction. The shape of the peaks in dI/dVdI/dV spectra originated from the structural change of the single molecule junction induced by the phonon excitation. The structural change could occur only for the Au/H2_{2}/Au junction. The difference in the two single molecule junctions could be explained by larger zero point energy of Au-H2_{2} vibration mode than that in the Au/H2_{2}/Au junction.Comment: 5 pages, 4 figures, to be appear in Phys. Rev.

    Electric Conductance of Rh Atomic Contacts under Electrochemical Potential Control

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    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 Φ0\Phi_{0}= 0.1 V vs. Ag/AgCl (Rh potential), the conductance histogram did not show any features. At Φ0\Phi_{0}= -0.1 V (under potential deposited hydrogen potential), the conductance histogram showed a feature around 2.3 G0G_{0} (G0G_{0} =2e2/he^{2}/h), which agreed with the conductance value of a clean Rh atomic contact, which was observed in ultrahigh vacuum at low temperature. At Φ0\Phi_{0}= -0.25 V (over potential deposited hydrogen potential), the conductance histogram showed features around 0.3 and 1.0 G0G_{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.Comment: 5 pages, 4 figures, Phys. Rev. B, in press

    Hydrogen-assisted stabilization of Ni nanowires in solution

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    We have studied conductance characteristics of mechanically fabricated Ni nanoconstrictions under controlling electrochemical potential and pH of the electrolyte. Conductance histogram showed clear feature peaked at 1-1.5 G0G_{0} (=2e2/h2e^{2}/h) when the potential of the constriction was kept at more negative potential than -900 mV vs. Ag/AgCl in pH=3.7. Comparable feature also appeared at more positive potential when lower pH solution was used. We have revealed that Ni mono atomic contact or mono atomic wire can be stabilized in solution at room temperature under the hydrogen evolution.Comment: 4 pages, 3 figures; to appear in Appl. Phys. Let

    Conductance of a single molecule anchored by an isocyanide substituent to gold electrodes

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    The effect of anchoring group on the electrical conductance of a single molecule bridging two Au electrodes was studied using di-substituted (isocyanide (CN-), thiol (S-) or cyanide (NC-)) benzene. The conductance of a single Au/1,4-diisocyanobenzene/Au junction anchored by isocyanide via a C atom (junction with the Au-CN bond) was 3×103G03 \times 10 ^{-3} G_{0} (2e2/h2e^{2}/h). The value was comparable to 4×103G04 \times 10 ^{-3} G_{0} of a single Au/1,4-benzenedithiol/Au junction with the Au-S bond. The Au/1,4-dicyanobenzene/Au molecular junction with the Au-NC bond did not show well-defined conductance values. The metal-molecule bond strength was estimated by the distance over which the molecular junction was stretched before breakdown. The stretched length of the molecular junction with the Au-CN bond was comparable to that of the Au junction, indicating that the Au-CN bond was stronger than the Au-Au bond.Comment: 3 figures, to be appear in Appl. Phys. Let

    Three reversible states controlled on a gold monoatomic contact by the electrochemical potential

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    Conductance of an Au mono atomic contact was investigated under the electrochemical potential control. The Au contact showed three different behaviors depending on the potential: 1 G0G_{0} (G0G_{0} = 2e2/h2e^{2}/h), 0.5 G0G_{0} and not-well defined values below 1 G0G_{0} were shown when the potential of the contact was kept at -0.6 V (double layer potential), -1.0 V (hydrogen evolution potential), and 0.8 V (oxide formation potential) versus Ag/AgCl in 0.1 M Na2_{2}SO4_{4} solution, respectively. These three reversible states and their respective conductances could be fully controlled by the electrochemical potential. These changes in the conductance values are discussed based on the proposed structure models of hydrogen adsorbed and oxygen incorporated on an Au mono atomic contact.Comment: 8 pages, 4 figures, to be appeared in Physical Review