Feng Yunxia, Chen Jinwei, Bâldea Ioan, Frisbie C Daniel, Xie Zuoti
Department of Materials Science and Engineering, Guangdong Provincial Key Laboratory of Materials and Technologies for Energy Conversion, Guangdong Technion-Israel Institute of Technology, Shantou, Guangdong 515063, China.
Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa 3200003, Israel.
JACS Au. 2025 Feb 14;5(3):1258-1267. doi: 10.1021/jacsau.4c01128. eCollection 2025 Mar 24.
Despite numerous prior studies on molecular tunnel junctions, many important questions remain about the nature of metal-molecule contacts. Using the conducting probe atomic force microscope (CP-AFM) platform, we report here an investigation of electrical contact effects in junctions based on oligophenylene and alkyl dithiols (OPD, = 1, 2, 3 and CDT, = 8, 9, 10) linked via thiol anchoring groups to dissimilar Ag, Au, and Pt metal electrodes. Our data reveal a peculiar effect: the two metal-molecule interfaces "talk" to each other, ., the choice of metal for the tip (t) electrode substantially changes the metal-HOMO electronic coupling Γ associated with the substrate (s) electrode, and vice versa. The metal-HOMO couplings Γ and Γ are not independent quantities. Their interdependence does not correlate with metal work function, chemisorption-driven work function change, or metal electronegativity, ., properties characterizing charge transfer at the molecule-metal interface. Overall, our results reveal an undiscovered complexity associated with electrical contacts in molecular tunnel junctions that must be considered in theoretical descriptions and ongoing efforts to design junctions with specific electronic functions.
尽管之前有许多关于分子隧道结的研究，但关于金属 - 分子接触的本质仍存在许多重要问题。利用导电探针原子力显微镜（CP - AFM）平台，我们在此报告了对基于通过硫醇锚定基团连接到不同的银、金和铂金属电极上的亚苯基和烷基二硫醇（OPD，n = 1、2、3和CDT，n = 8、9、10）的结中的电接触效应的研究。我们的数据揭示了一种奇特的效应：两个金属 - 分子界面相互“交流”，即，尖端（t）电极的金属选择会显著改变与基底（s）电极相关的金属 - 最高占据分子轨道（HOMO）电子耦合Γ，反之亦然。金属 - HOMO耦合Γt和Γs不是独立的量。它们的相互依赖性与金属功函数、化学吸附驱动的功函数变化或金属电负性无关，即与表征分子 - 金属界面电荷转移的性质无关。总体而言，我们的结果揭示了分子隧道结中与电接触相关的未被发现的复杂性，这在理论描述以及当前设计具有特定电子功能的结的努力中必须予以考虑。
