Statistical analysis of single-molecule junctions
Statistical analysis of single-molecule junctions
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DOI：
10.1002/anie.200301733
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发表时间：
2004-01-01
影响因子：
16.6
通讯作者：
Weber, HB
中科院分区：
文献类型：
--
作者：
Mayor, M;Weber, HB
多年来，将分子集成到电子电路中一直是一项科学挑战。这项研究是由科学兴趣和利用分子作为未来纳米电子学功能构建块的技术愿景驱动的。这种思想在今天被称为“分子电子学”然而，它起源于20世纪60年代末，当时汉斯·库恩（Hans Kuhn）提出了他的“分子工程”愿景在早期的研究中，理论预测[3]并尝试研究基于Langmuir-Blodgett薄膜的分子多层[2,4]和单层[5]结构。但是近年来，在binning和Rohrer发明的扫描隧道显微镜（STM）技术的推动下，纳米工程取得了巨大的进步，[6]重新激活了在电子电路中连接单个分子的想法。一些固定纳米单分子的实验，特别是共轭π体系，[7]配位化合物，[8]和DNA分子，[9]与电极对接触的实验已经被报道。观察到的电流输运特性在不同的研究中有所不同，因为在原子尺度上，不同实验中微观条件的可比性差，对结果影响很大。迄今为止，大多数使用STM、机械控制断结和电迁移制造的纳米电极进行的实验研究仅限于少数结。然而，当不是一个大的统计集合，而是单分子水平的探测，再现性和可比性本质上是有限的。因此，需要对单分子接触的大集合进行统计评价。这种方法已经在金属纳米结实验和由氢分子桥接的结中被证明可以产生额外的相关信息生成了出现的电导值的直方图，并允许检测“典型”接触配置。此外，扫描探针研究了基于嵌入自组装单层（SAMs）并由金簇覆盖的单分子的连接。[12,13]对这些结果的统计分析表明，许多曲线可以被识别为共同的“母曲线”的倍数，因此对应于接触分子的整数此外，物理参数变化的发生，如负微分电阻（NDR）效应的峰值位置，已经用直方图表征。[13,14]Xu和Tao最近利用STM.[15]在电化学实验中应用了这种统计方法来研究单分子结STM的金尖端反复与金衬底接触并再次拉开，从而连续形成数百个触点。当将尖端从表面拉出时，观察到金触点与几个原子的横截面的形成，这是通过电导率的逐步降低来检测的（每一步的电导率接近的倍数）
The integration of molecules into electronic circuits has been a scientific challenge for many years. The research is driven by both scientific interest as well as the technological vision of employing molecules as functional building blocks in future nanoelectronics. This idea is today termed “molecular electronics”.[1] However, it originates in the late 1960s when Hans Kuhn introduced his vision of “molecular engineering”.[2] In early studies, theoretical predictions [3] and attempts to investigate molecular multi-[2, 4] and monolayer [5] architectures based on Langmuir–Blodgett films were reported. But the enormous improvements in nanoscale engineering in recent years, driven by the invention of scanning-tunneling microscopy (STM) techniques by Binnig and Rohrer,[6] revitalized the idea of wiring an individual molecule in an electronic circuit. Several experiments with immobilized nanoscale single molecules, in particular conjugated π systems,[7] coordination compounds,[8] and DNA molecules,[9] in contact with electrode pairs have been reported. The observed current-transport characteristics vary between the different investigations because the, on the atomic scale, poorly comparable microscopic conditions in different experiments affect the results strongly. To date, most experimental studies carried out with STM, mechanically controlled break junctions, and electromigration-fabricated nanoelectrodes were limited to a small number of junctions. However, when instead of a large statistical ensemble, the singlemolecule level is probed, both reproducibility and comparability are intrinsically limited. Hence, a statistical evaluation of a large ensemble of singlemolecule contacts is desired. This approach has already proven to yield additional relevant information in metallic nanojunction experiments [10] and in junctions which are bridged by hydrogen molecules.[11] The histograms of the appearing conductance values were generated and allowed the detection of “typical” contact configurations. Further, scanning-probe investigations were carried out on junctions based on single molecules embedded in self-assembled monolayers (SAMs) and capped by gold clusters.[12, 13] The statistical analysis of these results showed that many curves could be identified as multiples of a common “parent curve” and hence correspond to an integer number of contacted molecules.[12] Also the occurrence of variations in physical parameters, such as, the peak position of negative differential resistance (NDR) effects, have been characterized with histograms.[13, 14]Xu and Tao recently applied such a statistical approach to investigate singlemolecule junctions in an electrochemical experiment by means of STM.[15] The gold tip of the STM is repeatedly brought into contact with the gold substrate and pulled off again, thus successively forming hundreds of contacts. On pulling the tip from the surface, the formation of gold contacts with cross sections of just a few atoms is observed, which is detected by a stepwise decrease of the conductance (the conductance of each step is close to multiples of the