Pabi Biswajit, Marek Štepán, Pal Adwitiya, Kumari Puja, Ray Soumya Jyoti, Thakur Arunabha, Korytár Richard, Pal Atindra Nath
Department of Condensed Matter and Materials Physics, S. N. Bose National Centre for Basic Sciences, Sector III, Block JD, Salt Lake, Kolkata 700106, India.
Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University, 121 16, Prague 2, Czech Republic.
Nanoscale. 2023 Aug 10;15(31):12995-13008. doi: 10.1039/d3nr02585c.
Achieving highly transmitting molecular junctions through resonant transport at low bias is key to the next-generation low-power molecular devices. Although resonant transport in molecular junctions was observed by connecting a molecule between the metal electrodes chemical anchors by applying a high source-drain bias (>1 V), the conductance was limited to <0.1, being the quantum of conductance. Herein, we report electronic transport measurements by directly connecting a ferrocene molecule between Au electrodes under ambient conditions in a mechanically controllable break junction setup (MCBJ), revealing a conductance peak at ∼0.2 in the conductance histogram. A similar experiment was repeated for ferrocene terminated with amine (-NH) and cyano (-CN) anchors, where conductance histograms exhibit an extended low conductance feature, including the sharp high conductance peak, similar to pristine ferrocene. The statistical analysis of the data and density functional theory-based transport calculation suggest a possible molecular conformation with a strong hybridization between the Au electrodes, and that the Fe atom of ferrocene is responsible for a near-perfect transmission in the vicinity of the Fermi energy, leading to the resonant transport at a small applied bias (<0.5 V). Moreover, calculations including van der Waals/dispersion corrections reveal a covalent-like organometallic bonding between Au and the central Fe atom of ferrocene, having bond energies of ∼660 meV. Overall, our study not only demonstrates the realization of an air-stable highly transmitting molecular junction, but also provides important insights about the nature of chemical bonding at the metal/organo-metallic interface.
通过低偏压下的共振输运实现高传导分子结是下一代低功耗分子器件的关键。尽管通过在金属电极之间连接分子化学锚并施加高源漏偏压（>1 V）观察到了分子结中的共振输运，但电导被限制在<0.1，即电导量子。在此，我们报告了在机械可控断裂结装置（MCBJ）的环境条件下，通过直接在金电极之间连接二茂铁分子进行的电子输运测量，在电导直方图中揭示了一个约为0.2的电导峰。对以胺基（-NH）和氰基（-CN）锚终止的二茂铁重复了类似实验，其中电导直方图呈现出扩展的低电导特征，包括尖锐的高电导峰，类似于原始二茂铁。数据的统计分析和基于密度泛函理论的输运计算表明，可能存在一种分子构象，在金电极之间具有强烈的杂化，并且二茂铁的铁原子在费米能附近负责近乎完美的传输，从而导致在小施加偏压（<0.5 V）下的共振输运。此外，包括范德华/色散校正的计算揭示了金与二茂铁中心铁原子之间类似共价的有机金属键，键能约为660 meV。总体而言，我们的研究不仅证明了实现空气稳定的高传导分子结，还提供了关于金属/有机金属界面化学键性质的重要见解。
