Mapping the Transmission Functions of Single-Molecule Junctions
Mapping the Transmission Functions of Single-Molecule Junctions
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DOI：
10.1021/acs.nanolett.6b01592
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发表时间：
2016-06-01
期刊：
影响因子：
10.8
通讯作者：
Venkataraman, Latha
中科院分区：
文献类型：
--
作者：
Capozzi, Brian;Low, Jonathan Z.;Venkataraman, Latha
单分子结中的电荷输运现象通常由隧穿作用主导，其传输函数决定了电子或空穴隧穿结的概率。在这里，我们提出了一种新的简单的技术来测量分子结在相干隧穿极限下的传输函数，在1.5 eV的能量范围内，在费米能量附近。我们在离子环境中创建分子结，电极具有不同的暴露面积，这导致在两个电极上形成不同密度的双电层：这使我们能够以一种依赖于施加偏压的符号的方式，静电地移动相对于结费米能级的分子共振，使我们能够绘制出结的传输函数，并确定分子结中电荷传输的主导轨道。我们用两组分子证明了这种技术：一组分子共振能量相对远离4，另一组分子共振能量在可达的偏置窗口内。我们的结果与以前的电化学门控数据以及从第一性原理计算的传输函数相比较。此外，对于第二组分子，我们能够检查共振转移到偏置窗口时分子结的行为。这项工作为探索纳米尺度上电荷输运的基本原理提供了一条新的、实验上简单的途径。
Charge transport phenomena in single-molecule junctions are often dominated by tunneling, with a transmission function dictating the probability that electrons or holes tunnel through the junction. Here, we :present a new and simple technique for measuring, the transmission functions of molecular junctions in the coherent tunneling limit, over an energy range of 1.5 eV around the Fermi energy. We create molecular junctions in an ionic environment with electrodes having different exposed areas, which results in the formation of electric double layets of dissimilar density on the two electrodes: This allows us to electrostatically shift the molecular resonance relative to the junction Fermi levels in a manner that depends on the sign of the applied bias, enabling us to map, out the junction's transmission function and determine the dominant orbital for charge transport in the molecular junction. We demonstrate, this technique using two groups of molecules: one group having molecular resonance energies relatively far from 4 and one group having molecular resonance energies within the accessible bias window. Our results compare well with previous electrochemical gating data, and with transmission functions computed from first principles. Furthermore, with the second group of molecules, We are able to examine the behavior of a molecular junction as a resonance shifts into the bias window. This work provides a new, experimentally simple route for exploring the fundamentals of charge transport at the nanoscale.