Conduction Mechanism of Aviram-Ratner Rectifiers with Single Pyridine--C60 Oligomers
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- 作者：Bing Wang ; Yunshen Zhou ; Xunlei Ding ; Kedong Wang ; Xiaoping Wang ; Jinlong Yang ; J. G. Hou
- 刊名：Journal of Physical Chemistry B
- 出版年：2006
- 出版时间：December 7, 2006
- 年：2006
- 卷：110
- 期：48
- 页码：24505 - 24512
- 全文大小：591K
- 年卷期：v.110,no.48(December 7, 2006)
- ISSN：1520-5207
文摘
We present the electron transport of pyridyl aza[60]fulleroid oligomers, abbreviated as C60NPy, which isbased on the donor-barrier-acceptor (D-
-A) architecture, at a single molecular scale using scanningtunneling microscopy. A rectifying effect is observed in the current-voltage characteristics. The theoreticalcalculation shows that the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecularorbital (LUMO) are well localized either on the Py moiety (donor) or on the C60 moiety (acceptor), indicatingthe -bridge decouples the LUMO and the HOMO of the donor and the acceptor, respectively. This structureaccords well with the unimolecular rectifying model proposed by Aviram and Ratner [Chem. Phys. Lett.1974, 29, 277]. The mechanism of the rectifying effect is understood by analyzing in detail the electrontransport through energy levels of the donor and the acceptor of the C60NPy molecules. By directly comparingthe experimental conductance peaks and the calculated density of states of the C60NPy, we find that theobserved rectification is attributed to the asymmetric positioning of the LUMOs and the HOMOs of bothsides of the acceptor and the donor of the C60NPy molecules with respect to the Fermi level of the electrodes.When a main voltage drop is over the molecule-electrode vacuum junction but a small fraction over themolecule itself, the shift of the energy levels between the donor and the acceptor will be small. This behaviordeviates from the original proposal by Aviram and Ratner in which a large shift of the energy level is expected.
-A) architecture, at a single molecular scale using scanningtunneling microscopy. A rectifying effect is observed in the current-voltage characteristics. The theoreticalcalculation shows that the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecularorbital (LUMO) are well localized either on the Py moiety (donor) or on the C60 moiety (acceptor), indicatingthe -bridge decouples the LUMO and the HOMO of the donor and the acceptor, respectively. This structureaccords well with the unimolecular rectifying model proposed by Aviram and Ratner [Chem. Phys. Lett.1974, 29, 277]. The mechanism of the rectifying effect is understood by analyzing in detail the electrontransport through energy levels of the donor and the acceptor of the C60NPy molecules. By directly comparingthe experimental conductance peaks and the calculated density of states of the C60NPy, we find that theobserved rectification is attributed to the asymmetric positioning of the LUMOs and the HOMOs of bothsides of the acceptor and the donor of the C60NPy molecules with respect to the Fermi level of the electrodes.When a main voltage drop is over the molecule-electrode vacuum junction but a small fraction over themolecule itself, the shift of the energy levels between the donor and the acceptor will be small. This behaviordeviates from the original proposal by Aviram and Ratner in which a large shift of the energy level is expected.