Rectification and stability of a single molecular diode with controlled orientation


In the molecular electronics field it is highly desirable to engineer the structure of molecules to achieve specific functions. In particular, diode (or rectification) behaviour in single molecules is an attractive device function. Here we study charge transport through symmetric tetraphenyl and non-symmetric diblock dipyrimidinyldiphenyl molecules covalently bound to two electrodes. The orientation of the diblock is controlled through a selective deprotection strategy, and a method in which the electrode–electrode distance is modulated unambiguously determines the current–voltage characteristics of the single-molecule device. The diblock molecule exhibits pronounced rectification behaviour compared with its homologous symmetric block, with current flowing from the dipyrimidinyl to the diphenyl moieties. This behaviour is interpreted in terms of localization of the wave function of the hole ground state at one end of the diblock under the applied field. At large forward current, the molecular diode becomes unstable and quantum point contacts between the electrodes form.

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Figure 1: Preparation of the SAMs.
Figure 2: Current traces and conductance histograms for the symmetric and non-symmetric molecules.
Figure 3: Components of the current traces during a single dipyrimidinyl–diphenyl bridge formation.
Figure 4: Current-voltage (I–V) curves for the symmetric and non-symmetric molecules.
Figure 5: Two types of instability behaviours of the molecular junctions.
Figure 6: Representation of the rectification mechanism for the non-symmetric molecule.


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We thank the National Science Foundation (I.D.-P., Y.L., L.Y., L.A., I.I.O. and N.J.T.), Department of Energy (J.H. and N.J.T.) and the Marie-Curie M.C.-I.O.F. within the European Commission Seventh Framework program (I.D.-P.) for financial support.

Author information




N.J.T. and L.Y. conceived this project. I.D.-P. and J.H. conducted experiments and analysed data. Y.L. synthesized the molecules. I.I.O. designed and supervised the theoretical study and L.A. and M.A.K. did the calculations.

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Correspondence to Luping Yu or Nongjian Tao.

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Díez-Pérez, I., Hihath, J., Lee, Y. et al. Rectification and stability of a single molecular diode with controlled orientation. Nature Chem 1, 635–641 (2009).

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