Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
J Phys Condens Matter. 2012 Oct 3;24(39):394002. doi: 10.1088/0953-8984/24/39/394002. Epub 2012 Sep 11.
Using scanning tunneling spectroscopy, we study the transport of electrons through C(60) molecules on different metal surfaces. When electrons tunnel through a molecule, they may excite molecular vibrations. A fingerprint of these processes is a characteristic sub-structure in the differential conductance spectra of the molecular junction reflecting the onset of vibrational excitation. Although the intensity of these processes is generally weak, they become more important as the resonant character of the transport mechanism increases. The detection of single vibrational levels crucially depends on the energy level alignment and lifetimes of excited states. In the limit of large current densities, resonant electron-vibration coupling leads to an energy accumulation in the molecule, which eventually leads to its decomposition. With our experiments on C(60) we are able to depict a molecular scale picture of how electrons interact with the vibrational degrees of freedom of single molecules in different transport regimes. This understanding helps in the development of stable molecular devices, which may also carry a switchable functionality.
利用扫描隧道谱，我们研究了电子在不同金属表面穿过 C(60)分子的输运过程。当电子通过分子隧道时，它们可能会激发分子振动。这些过程的一个特征指纹是分子结的微分电导谱中的一个特征子结构，反映了振动激发的开始。尽管这些过程的强度通常较弱，但随着输运机制的共振特征增加，它们变得更加重要。单个振动能级的检测在很大程度上取决于激发态的能级排列和寿命。在大电流密度的极限下，共振电子-振动耦合会导致分子中的能量积累，最终导致其分解。通过我们对 C(60)的实验，我们能够描绘出一个分子尺度的图景，展示电子在不同输运机制下如何与单个分子的振动自由度相互作用。这种理解有助于开发稳定的分子器件，这些器件也可能具有可切换的功能。
