Conductance of Tailored Molecular Segments: A Rudimentary Assessment by Landauer Formulation

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• 作者：Min-Jie Huang ; Liang-Yan Hsu ; Ming-Dung Fu ; Su-Ting Chuang ; Fang-Wei Tien ; Chun-hsien Chen
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：February 5, 2014
• 年：2014
• 卷：136
• 期：5
• 页码：1832-1841
• 全文大小：562K
• ISSN：1520-5126

文摘

One of the strengths of molecular electronics is the synthetic ability of tuning the electric properties by the derivatization and reshaping of the functional moieties. However, after the quantitative measurements of single-molecule resistance became available, it was soon apparent that the assumption of negligible influence of the headgroup鈥揺lectrode contact on the molecular resistance was oversimplified. Due to the measurement scheme of the metal鈥?molecule鈥搈etal configuration, the contact resistance is always involved in the reported values. Consequently the electrical behavior of the tailored molecular moiety can only be conceptually inferred by the tunneling decay constant (尾_n in R_measured = R_n=0e^尾nN, where N is the number of repeated units), available only for compounds with a homologous series. This limitation hampers the exploration of novel structures for molecular devices. Based on the Landauer formula, we propose that the single-molecule resistance of the molecular backbones can be extracted. This simplified evaluation scheme is cross-examined by electrode materials of Au, Pd, and Pt and by anchoring groups of thiol (鈭扴H), nitrile (鈭扖N), and isothiocyanate (鈭扤CS). The resistance values of molecular backbones for polymethylenes (n = 4, 6, 8, and 10) and phenyl (鈭扖₆H₄鈭? moieties are found independent of the anchoring groups and electrode materials. The finding justifies the proposed approach that the resistance of functional moieties can be quantitatively evaluated from the measured values even for compounds without repeated units.