Beebe Jeremy M, Kim BongSoo, Frisbie C Daniel, Kushmerick James G
National Institute of Standards and Technology, Gaithersburg, Maryland, 20899, USA.
ACS Nano. 2008 May;2(5):827-32. doi: 10.1021/nn700424u.
Though molecular devices exhibiting potentially useful electrical behavior have been demonstrated, a deep understanding of the factors that influence charge transport in molecular electronic junctions has yet to be fully realized. Recent work has shown that a mechanistic transition occurs from direct tunneling to field emission in molecular electronic devices. The magnitude of the voltage required to enact this transition is molecule-specific, and thus measurement of the transition voltage constitutes a form of spectroscopy. Here we determine that the transition voltage for a series of alkanethiol molecules is invariant with molecular length, while the transition voltage of a conjugated molecule depends directly on the manner in which the conjugation pathway has been extended. Finally, by examining the transition voltage as a function of contact metal, we show that this technique can be used to determine the dominant charge carrier for a given molecular junction.
尽管已证明分子器件展现出潜在有用的电学行为，但对影响分子电子结中电荷传输的因素仍未完全深入理解。近期研究表明，分子电子器件中会发生从直接隧穿到场发射的机制转变。引发这种转变所需的电压大小因分子而异，因此对转变电压的测量构成了一种光谱学形式。在此我们确定，一系列链烷硫醇分子的转变电压与分子长度无关，而共轭分子的转变电压直接取决于共轭路径的扩展方式。最后，通过研究作为接触金属函数的转变电压，我们表明该技术可用于确定给定分子结的主要电荷载流子。
