Obersteiner Veronika, Egger David A, Zojer Egbert
Institute of Solid State Physics, NAWI Graz, Graz University of Technology , Petersgasse 16, 8010 Graz, Austria.
Institute of Solid State Physics, NAWI Graz, Graz University of Technology , Petersgasse 16, 8010 Graz, Austria ; Department of Materials and Interfaces, Weizmann Institute of Science , Rehovoth 76100, Israel.
J Phys Chem C Nanomater Interfaces. 2015 Sep 10;119(36):21198-21208. doi: 10.1021/acs.jpcc.5b06110. Epub 2015 Aug 13.
Tuning the transport properties of molecular junctions by chemically modifying the molecular structure is one of the key challenges for advancing the field of molecular electronics. In the present contribution, we investigate current-voltage characteristics of differently linked metal-molecule-metal systems that comprise either a single molecule or a molecular assembly. This is achieved by employing density functional theory in conjunction with a Green's function approach. We show that the conductance of a molecular system with a specific anchoring group is fundamentally different depending on whether a single molecule or a continuous monolayer forms the junction. This is a consequence of collective electrostatic effects that arise from dipolar elements contained in the monolayer and from interfacial charge rearrangements. As a consequence of these collective effects, the "ideal" choice for an anchoring group is clearly different for monolayer and single molecule devices. A particularly striking effect is observed for pyridine-docked systems. These are subject to Fermi-level pinning at high molecular packing densities, causing an abrupt increase of the junction current already at small voltages.
通过化学修饰分子结构来调节分子结的输运性质是推动分子电子学领域发展的关键挑战之一。在本论文中，我们研究了由单个分子或分子组装体组成的不同连接方式的金属-分子-金属体系的电流-电压特性。这是通过将密度泛函理论与格林函数方法相结合来实现的。我们表明，具有特定锚定基团的分子体系的电导，根据形成结的是单个分子还是连续单层而有根本差异。这是由单层中包含的偶极元素和界面电荷重排产生的集体静电效应的结果。由于这些集体效应，对于单层和单分子器件，锚定基团的“理想”选择明显不同。对于吡啶对接体系观察到了特别显著的效应。在高分子堆积密度下，这些体系会发生费米能级钉扎，导致在小电压下结电流就急剧增加。
