In situ formation of highly conducting covalent Au-C contacts for single-molecule junctions
In situ formation of highly conducting covalent Au-C contacts for single-molecule junctions
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DOI：
10.1038/nnano.2011.66
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发表时间：
2011-06-01
影响因子：
38.3
通讯作者：
Venkataraman, L.
中科院分区：
文献类型：
--
作者：
Cheng, Z. -L.;Skouta, R.;Venkataraman, L.
金属-分子界面的电荷传输在有机电子学中具有重要作用（1）。通常，化学连接基团如硫醇（2）或胺（3）用于将有机分子结合到单分子电路中的金属电极上，这些基团控制界面处的物理结构和电子耦合。直接的金属-碳偶联已经通过C60、苯和p-堆叠的苯（4-7）示出，但是理想地，分子的碳主链应该共价键合到电极而没有插入的连接基团。在这里，我们演示了一种方法来创建与这种接触的交界处。三甲基锡（SnMe 3）封端的聚亚甲基链用于通过断裂连接技术形成单分子连接（2，3）。电极上的金原子取代了SnMe 3连接体，导致直接Au-C键合的单分子结的形成，其电导率类似于具有大多数其他终端的类似烷烃的100倍。这些Au-C键合烷烃的电导随分子长度呈指数下降，衰减常数为0.97每亚甲基，符合非共振传输机制。控制实验和从头计算表明，由于形成了共价Au-C σ（σ）键，实现了高电导。这提供了一种用于制造可再现的和高导电的金属-有机接触的新方法。
Charge transport across metal-molecule interfaces has an important role in organic electronics(1). Typically, chemical link groups such as thiols(2) or amines(3) are used to bind organic molecules to metal electrodes in single-molecule circuits, with these groups controlling both the physical structure and the electronic coupling at the interface. Direct metal-carbon coupling has been shown through C60, benzene and p-stacked benzene(4-7), but ideally the carbon backbone of the molecule should be covalently bonded to the electrode without intervening link groups. Here, we demonstrate a method to create junctions with such contacts. Trimethyl tin (SnMe3)-terminated polymethylene chains are used to form single-molecule junctions with a break-junction technique(2,3). Gold atoms at the electrode displace the SnMe3 linkers, leading to the formation of direct Au-C bonded single-molecule junctions with a conductance that is similar to 100 times larger than analogous alkanes with most other terminations. The conductance of these Au-C bonded alkanes decreases exponentially with molecular length, with a decay constant of 0.97 per methylene, consistent with a non-resonant transport mechanism. Control experiments and ab initio calculations show that high conductances are achieved because a covalent Au-C sigma (sigma) bond is formed. This offers a new method for making reproducible and highly conducting metal-organic contacts.