Acta Phys. -Chim. Sin. ›› 2015, Vol. 31 ›› Issue (8): 1474-1482.doi: 10.3866/PKU.WHXB201506112

• THEORETICALAND COMPUTATIONAL CHEMISTRY • Previous Articles     Next Articles

Theoretical Investigation of the Transition Voltages of Cu-Vacuum-Cu Tunneling Junctions

Mei-Lin. BAI1,Ming-Lang. WANG1,Shi-Min. HOU1,2,*()   

  1. 1 Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing 100871, P. R. China
    2 Beida Beida Information Research BIR, Tianjin 300457, P. R. China
  • Received:2015-04-30 Published:2015-08-12
  • Contact: Shi-Min. HOU E-mail:smhou@pku.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(61321001);National Key Basic Research Program of China(973)(2011CB933001, 2013CB933404)

Abstract:

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.

Key words: Vacuum tunneling, Transition voltage spectroscopy, Electron transport, Non-equilibrium Green's function, Density functional theory

MSC2000: 

  • O641