Kristensen I S, Mowbray D J, Thygesen K S, Jacobsen K W
Center for Atomic-scale Materials Design (CAMD), Department of Physics, Building 307, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
J Phys Condens Matter. 2008 Sep 17;20(37):374101. doi: 10.1088/0953-8984/20/37/374101. Epub 2008 Aug 26.
The electrical properties of single-molecule junctions, consisting of an organic molecule coupled to metal electrodes, are sensitive to the detailed atomic structure of the molecule-metal contact. This, in turn, is determined by the anchoring group linking the molecule to the metal. With the aim of identifying and comparing the intrinsic properties of two commonly used anchoring groups, namely thiol and amine groups, we have calculated the atomic structure and conductance traces of different Au-S-Au and Au-NH(2)-Au nanojunctions using density functional theory (DFT). Whereas NH(2) shows a strong structural selectivity towards atop-gold configurations, S shows large variability in its bonding geometries. As a result, the conductance of the Au-NH(2)-Au junction is less sensitive to the structure of the gold contacts than the Au-S-Au junction. These findings support recent experiments which show that amine-bonded molecules exhibit more well-defined conductance properties than do thiol-bonded molecules.
由与金属电极相连的有机分子构成的单分子结的电学性质，对分子与金属接触的详细原子结构敏感。反过来，这又由将分子连接到金属的锚定基团决定。为了识别和比较两种常用锚定基团（即硫醇基和胺基）的内在性质，我们使用密度泛函理论（DFT）计算了不同Au-S-Au和Au-NH₂-Au纳米结的原子结构和电导曲线。NH₂对金顶位构型表现出很强的结构选择性，而S在其键合几何结构上表现出很大的变异性。因此，Au-NH₂-Au结的电导对金接触结构的敏感性低于Au-S-Au结。这些发现支持了最近的实验，该实验表明胺键合分子比硫醇键合分子表现出更明确的电导性质。
