Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Mechanically controlled molecular orbital alignment in single molecule junctions


Research in molecular electronics often involves the demonstration of devices that are analogous to conventional semiconductor devices, such as transistors and diodes1, but it is also possible to perform experiments that have no parallels in conventional electronics. For example, by applying a mechanical force to a molecule bridged between two electrodes, a device known as a molecular junction, it is possible to exploit the interplay between the electrical and mechanical properties of the molecule to control charge transport through the junction2,3,4,5,6,7,8. 1,4′-Benzenedithiol is the most widely studied molecule in molecular electronics9,10,11,12,13,14,15,16,17,18, and it was shown recently that the molecular orbitals can be gated by an applied electric field11. Here, we report how the electromechanical properties of a 1,4′-benzenedithiol molecular junction change as the junction is stretched and compressed. Counterintuitively, the conductance increases by more than an order of magnitude during stretching, and then decreases again as the junction is compressed. Based on simultaneously recorded current–voltage and conductance–voltage characteristics, and inelastic electron tunnelling spectroscopy, we attribute this finding to a strain-induced shift of the highest occupied molecular orbital towards the Fermi level of the electrodes, leading to a resonant enhancement of the conductance. These results, which are in agreement with the predictions of theoretical models14,15,16,17,19,20, also clarify the origins of the long-standing discrepancy between the calculated and measured conductance values of 1,4′-benzenedithiol, which often differ by orders of magnitude21.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Changes in conductance of BDT due to stretching.
Figure 2: Differential conductance and IETS of BDT junctions as a result of stretching and compressing.
Figure 3: Conductance switching behaviour of two BDT junctions.
Figure 4: Exploring the energy levels of a molecular junction.


  1. 1

    Aviram, A. & Ratner, M. Molecular rectifiers. Chem. Phys. Lett. 29, 277–283 (1974).

    CAS  Article  Google Scholar 

  2. 2

    Joachim, C., Gimzewski, J. K. & Aviram, A. Electronics using hybrid-molecular and mono-molecular devices. Nature 408, 541–548 (2000).

    CAS  Article  Google Scholar 

  3. 3

    Xu, Bingqian et al. Electromechanical and conductance switching properties of single oligothiophene molecules. Nano Lett. 5, 1491–1495 (2005).

    CAS  Article  Google Scholar 

  4. 4

    Parks, J. J. et al. Mechanical control of spin states in spin-1 molecules and the underscreened Kondo effect. Science 328, 1370–1373 (2010).

    CAS  Article  Google Scholar 

  5. 5

    Meisner, J. S. et al. A single-molecule potentiometer. Nano Lett. 11, 1575–1579 (2011).

    CAS  Article  Google Scholar 

  6. 6

    Quek, S. Y. et al. Mechanically controlled binary conductance switching of a single-molecule junction. Nature Nanotech. 4, 230–234 (2009).

    CAS  Article  Google Scholar 

  7. 7

    Diez-Perez, I. et al. Controlling single molecule conductance through lateral coupling of π-orbitals. Nature Nanotech. 6, 226–231 (2011).

    CAS  Article  Google Scholar 

  8. 8

    Kim, Y. et al. Conductance and vibrational states of single-molecule junctions controlled by mechanical stretching and material variation. Phys. Rev. Lett. 106, 196804 (2011).

    Article  Google Scholar 

  9. 9

    Xiao, X. Y., Xu, B. Q & Tao, N. J. Measurement of single molecule conductance: benzenedithiol and benzenedimethanethiol. Nano Lett. 4, 267–271 (2004).

    CAS  Article  Google Scholar 

  10. 10

    Reed, M. A. et al. Conductance of a molecular junction. Science 278, 252–254 (1997).

    CAS  Article  Google Scholar 

  11. 11

    Song, H. et al. Observation of molecular orbital gating. Nature 462, 1039–1043 (2009).

    CAS  Article  Google Scholar 

  12. 12

    Tsutsui, M., Teramae, Y., Kurokawa, S. & Sakai, A. High-conductance states of single benzenedithiol molecules. Appl. Phys. Lett. 89, 163111 (2006).

    Article  Google Scholar 

  13. 13

    Taniguchi, M., Tsutsui, M., Yokota, K. & Kawai, T. Inelastic electron tunneling spectroscopy of single-molecule junctions using a mechanically controllable break junction. Nanotechnology 20, 434008 (2009).

    Article  Google Scholar 

  14. 14

    Romaner, L. et al. Stretching and breaking of a molecular junction. Small 2, 1468–1475 (2006).

    CAS  Article  Google Scholar 

  15. 15

    Ke, S. H., Baranger, H. U. & Yang, W. T. Contact atomic structure and electron transport through molecules. J. Chem. Phys. 122, 074704 (2005).

    Article  Google Scholar 

  16. 16

    Li, Z. & Kosov, D. S. Nature of well-defined conductance of amine-anchored molecular junctions: density functional calculations. Phys. Rev. B 76, 035415 (2007).

    Article  Google Scholar 

  17. 17

    Xue, Y. & Ratner, M. A. Microscopic study of electrical transport through individual molecules with metallic contacts. II. Effect of the interface structure. Phys. Rev. B. 68, 115406 (2003).

    Article  Google Scholar 

  18. 18

    Kim, Y. et al. Benzenedithiol: a broad-range single-channel molecular conductor. Nano Lett. 11, 3734–3738 (2011).

    CAS  Article  Google Scholar 

  19. 19

    Toher, C. & Sanvito, S. Efficient atomic self-interaction correction scheme for nonequilibrium quantum transport. Phys. Rev. Lett. 99, 056801 (2007).

    CAS  Article  Google Scholar 

  20. 20

    Pontes, R. B. et al. Ab initio calculations of structural evolution and conductance of benzene-1,4-dithiol on gold leads. ACS Nano 5, 795–804 (2011).

    CAS  Article  Google Scholar 

  21. 21

    Lindsay, S. M. & Ratner, M. A. Molecular transport junctions: clearing mists. Adv. Mater. 19, 23–31 (2007).

    CAS  Article  Google Scholar 

  22. 22

    Xu, B. Q. & Tao, N. J. Measurement of single molecule conductance by repeated formation of molecular junctions. Science 301, 1221–1223 (2003).

    CAS  Article  Google Scholar 

  23. 23

    Smit, R. H. M. et al. Measurement of the conductance of a hydrogen molecule. Nature 419, 906–909 (2002).

    CAS  Article  Google Scholar 

  24. 24

    Hihath, J. & Tao, N. J. Rapid measurement of single-molecule conductance. Nanotechnology 19, 265204 (2008).

    Article  Google Scholar 

  25. 25

    Haiss, W. et al. Precision control of single-molecule electrical junctions. Nature Mater. 5, 995–1002 (2006).

    CAS  Article  Google Scholar 

  26. 26

    Zhou, J. F. & Xu, B. Q. Determining contact potential barrier effects on electronic transport in single molecular junctions. Appl. Phys. Lett. 99, 042104 (2011).

    Article  Google Scholar 

  27. 27

    Sergueev, N., Tsetseris, L., Varga, K. & Pantelides, S. Configuration and conductance evolution of benzene–dithiol molecular junctions under elongation. Phys. Rev. B 82, 073106 (2010).

    Article  Google Scholar 

  28. 28

    Hihath, J., Bruot, C. & Tao, N. J. Electron–phonon interactions in single octanedithiol molecular junctions. ACS Nano 4, 3823–3830 (2010).

    CAS  Article  Google Scholar 

  29. 29

    Luo, Y., Lin, L. L. & Wang, C. K. Inelastic electron tunneling spectroscopy of gold–benzenedithiol–gold junctions: accurate determination of molecular conformation. ACS Nano 5, 2257–2263 (2011).

    Article  Google Scholar 

  30. 30

    Chen, Y. C., Zwolak, M. & Di Ventra, M. Inelastic current–voltage characteristics of atomic and molecular junctions. Nano Lett. 4, 1709–1712 (2004).

    CAS  Article  Google Scholar 

  31. 31

    Agrait, N., Untiedt, C., Rubio-Bollinger, G. & Vieira, S. Onset of energy dissipation in ballistic atomic wires. Phys. Rev. Lett. 88, 216803 (2002).

    Article  Google Scholar 

  32. 32

    Arroyo, C. R. et al. Characterization of single-molecule pentanedithiol junctions by inelastic electron tunneling spectroscopy and first-principles calculations. Phys. Rev. B 81, 075405 (2010).

    Article  Google Scholar 

  33. 33

    Kamenetska, M. et al. Formation and evolution of single-molecule junctions. Phys. Rev. Lett. 102, 126803 (2009).

    CAS  Article  Google Scholar 

  34. 34

    Taniguchi, M., Tsutsui, M., Yokota, K. & Kawai, T. Mechanically-controllable single molecule switch based on configuration specific electrical conductivity of metal–molecule–metal junctions. Chem. Sci. 1, 247–253 (2010).

    CAS  Article  Google Scholar 

  35. 35

    Okabayashi, N., Konda, Y. & Komeda, T. Inelastic electron tunneling spectroscopy of an alkanethiol self-assembled monolayer using scanning tunneling microscopy. Phys. Rev. Lett. 100, 217801 (2008).

    Article  Google Scholar 

  36. 36

    Galperin, M., Ratner, M. A. & Nitzan, A. Inelastic electron tunneling spectroscopy in molecular junctions: peaks and dips. J. Chem. Phys. 121, 11965–11979 (2004).

    CAS  Article  Google Scholar 

  37. 37

    Paulsson, M. et al. Unified description of inelastic propensity rules for electron transport through nanoscale junctions. Phys. Rev. Lett. 100, 226604 (2008).

    Article  Google Scholar 

  38. 38

    Beebe, J. M., Kim, B., Frisbie, C. D. & Kushmerick, J. G. Measuring relative barrier heights in molecular electronic junctions with transition voltage spectroscopy. ACS Nano 2, 827–832 (2008).

    CAS  Article  Google Scholar 

  39. 39

    Huisman, E. H., Guedon, C. M., van Wees, B. J. & van der Molen, S. J. Interpretation of transition voltage spectroscopy. Nano Lett. 9, 3909–3913 (2009).

    CAS  Article  Google Scholar 

  40. 40

    Trouwborst, M. L. et al. Transition voltage spectroscopy and the nature of vacuum tunneling. Nano Lett. 11, 614–617 (2011).

    CAS  Article  Google Scholar 

Download references


This work was supported by the Basic Energy Science programme of the Department of Energy (DE-FG03-01ER45943, C.B.) and the National Science Foundation (CHE-1105588 and ECS-0925498, J.H. and N.J.T.).

Author information




N.J.T. conceived the experiment. C.B. and J.H. performed the experiment and analysed the data. C.B., J.H. and N.J.T. co-wrote the paper.

Corresponding author

Correspondence to Nongjian Tao.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary information

Supplementary information (PDF 1745 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Bruot, C., Hihath, J. & Tao, N. Mechanically controlled molecular orbital alignment in single molecule junctions. Nature Nanotech 7, 35–40 (2012).

Download citation

Further reading


Quick links

Find nanotechnology articles, nanomaterial data and patents all in one place. Visit Nano by Nature Research