Entity

Time filter

Source Type


Bai M.L.,Peking University | Wang M.L.,Peking University | Hou S.M.,Peking University | Hou S.M.,Beida Information Research BIR
Wuli Huaxue Xuebao/ Acta Physico - Chimica Sinica | Year: 2015

The transition voltage of copper-vacuum-copper tunneling junctions with atomic protrusions on the electrode surface was investigated using the non-equilibrium Green’s function formalism combined with density functional theory. Our calculations show that the transition voltages of Cu-vacuum-Cu junctions with atomically sharp electrodes are mainly determined by the local density of state (LDOS) of the 4p atomic orbitals of the protrusion, and are thus sensitive to the electrode orientation and the variation of the atomic configurations of surface protrusions. For Cu-vacuum-Cu junctions with (111)-oriented electrodes, the transition voltages were calculated to be about 1.40 and 2.40 V when the atomic protrusions were chosen to be one Cu adatom or a copper cluster with four atoms arranged in a pyramid configuration, respectively. The transition voltages of Cu-vacuum-Cu junctions with (100)-oriented electrodes were more different. When the atomic protrusion on the Cu(100) surface was a copper cluster with five atoms arranged in a pyramid configuration, the transition voltage was 1.70 V. In contrast, no transition voltage was observed for Cuvacuum- Cu junctions with one Cu adatom attached to the Cu(100) electrode surface even when the bias exceeded 1.80 V, which is caused by the LDOS of the 4p atomic orbitals of the Cu adatom on the Cu(100) surface being too extended. These results demonstrate the advantages of transition voltage spectroscopy as a tool for analyzing the electronic transport properties of metal-vacuum-metal tunneling junctions. © 2015, Editorial office of Acta Physico-Chimica Sinica.


Jiang Z.,University of Science and Technology Beijing | Wang H.,University of Science and Technology Beijing | Sanvito S.,Trinity College Dublin | Hou S.,University of Science and Technology Beijing | Hou S.,Beida Information Research BIR
Physical Review B - Condensed Matter and Materials Physics | Year: 2016

The evolution of the atomic structure and the vibrational and electronic transport properties of gold atomic junctions incorporating molecular and atomic hydrogen upon elongation have been investigated with the nonequilibrium Green's function formalism combined with density functional theory. Our calculations show that for the case of gold junctions doped with a single H2 molecule the low-bias conductance drops rapidly with the electrodes' separation, while it remains almost constant if a single H atom replaces the molecule. In contrast, when one considers two H atoms adsorbed on a gold monatomic chain forming an Au-H-Au-H-Au double-bridge structure, the low-bias conductance increases first and then shows a plateau upon stretching the junction, in perfect agreement with experiments on gold nanocontacts in hydrogen environment. Furthermore, also the distribution of the calculated vibrational energies of the two H atoms is consistent with the experimental result in the low-conductance region, demonstrating clear evidence that hydrogen molecules can dissociate on stretched gold monatomic chains. These findings are helpful to improve our understanding of the structure-property relation of gold nanocontacts and also provide a new prospect for gold nanowires being used as chemical sensors and catalysts. © 2016 American Physical Society.


Jiang Z.,University of Science and Technology Beijing | Wang H.,University of Science and Technology Beijing | Sanvito S.,Trinity College Dublin | Hou S.,University of Science and Technology Beijing | Hou S.,Beida Information Research BIR
Journal of Chemical Physics | Year: 2015

Inelastic electron tunneling spectroscopy (IETS) of a single hydrogen atom on the Cu(100) surface in a scanning tunneling microscopy (STM) configuration has been investigated by employing the non-equilibrium Green's function formalism combined with density functional theory. The electron-vibration interaction is treated at the level of lowest order expansion. Our calculations show that the single peak observed in the previous STM-IETS experiments is dominated by the perpendicular mode of the adsorbed H atom, while the parallel one only makes a negligible contribution even when the STM tip is laterally displaced from the top position of the H atom. This propensity of the IETS is deeply rooted in the symmetry of the vibrational modes and the characteristics of the conduction channel of the Cu-H-Cu tunneling junction, which is mainly composed of the 4s and 4pz atomic orbitals of the Cu apex atom and the 1s orbital of the adsorbed H atom. These findings are helpful for deepening our understanding of the propensity rules for IETS and promoting IETS as a more popular spectroscopic tool for molecular devices. © 2015 AIP Publishing LLC.


Xiang A.,Peking University | Wang M.,Peking University | Wang H.,Peking University | Sun H.,Peking University | And 3 more authors.
Chemical Physics | Year: 2016

We studied the origin of the transition voltage of octanedithiol (C8DT) molecules sandwiched between two gold electrodes. Au-C8DT-Au molecular junctions were fabricated using the feedback controlled electromigration technique. The conductance measurement and the inelastic electron tunneling spectrum validate that the observed current-voltage characteristics indeed originate from the C8DT molecule in the junction. The transition voltage of Au-C8DT-Au junctions is determined to be about 0.95 V, which cannot be interpreted using the energy difference between the highest occupied molecular orbital or lowest unoccupied molecular orbital of the alkyl chain and the Fermi level of electrodes. Instead, we relate the measured transition voltage to the Au-S bonds, which are about 1.4 eV below the gold Fermi level. Our interpretation is supported by the ultraviolet photoelectron spectroscopy measurements and first-principles quantum transport simulations. These findings provide convincing evidence that the Au-S occupied states play a significant role in the charge transport of Au-alkanedithiol-Au molecular devices. © 2015 Elsevier B.V. All rights reserved.


Karan S.,University of Kiel | Li N.,Peking University | Zhang Y.,Peking University | He Y.,Peking University | And 14 more authors.
Physical Review Letters | Year: 2016

All-trans-retinoic acid (ReA), a closed-shell organic molecule comprising only C, H, and O atoms, is investigated on a Au(111) substrate using scanning tunneling microscopy and spectroscopy. In dense arrays single ReA molecules are switched to a number of states, three of which carry a localized spin as evidenced by conductance spectroscopy in high magnetic fields. The spin of a single molecule may be reversibly switched on and off without affecting its neighbors. We suggest that ReA on Au is readily converted to a radical by the abstraction of an electron. © 2016 American Physical Society.

Discover hidden collaborations