電極材料對單分子電性之影響：修飾單層鉍原子之金電極對飽和烷雙頭酸的導電值量測

Conductance Measurements of Alkanedicarboxylic Acids on Gold Electrodes Modified by Underpotentially Deposited Bismuth Monolayer

陳常明(Chang-Ming Chen)

指導教授 ： 陳俊顯

國立臺灣大學/理學院/化學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.02590

摘要

分子電子學的領域中，分子電性的量測在金屬−分子−金屬(MMM, metal-molecule-metal)的架構下進行，因此單分子電性的量測值除了受到分子主體的傳遞效率影響，分子與電極間的交互作用也會影響量測結果，良好的分子−電極交互作用會提高電子在接合點的傳遞效率，使分子的導電性提高。本論文以低電位沉積法(UPD, underpotential deposition)修飾單層鉍原子(Bi, bismuth)的金作為電極材料，運用掃描式穿隧顯微術斷裂接合法(STM BJ, scanning tunneling microscopy-based break junction)及導電式原子力顯微術斷裂接合法(C-AFM, conductive-atomic force microscopy)斷裂接合法(C-AFM BJ)量測飽和烷雙頭酸之導電值。結果發現金電極修飾了Bi UPD與未修飾相比，以前者所測得的飽和烷雙頭酸分子較為導電，相差一個數量級。藉由計算導電值衰減常數(tunneling decay constant)及轉換電壓能譜(transition voltage spectroscopy)確認導電值的提升與分子主體的傳遞效率無關，意即修飾電極測得之導電性提升現象來自電極−分子接觸界面的傳遞效率改善。文獻報導羧酸官能基與修飾後的電極表面交互作用力增強，此外，理論計算中酸根分子與修飾後電極間的束縛能遠大於純金電極，上述原因皆使電子在MMM接合面的傳遞效率增加並提升導電值。

關鍵字

分子電性 ； 飽和烷雙頭酸

並列摘要

An important goal in molecular electronics is to measure and control electron transport through a molecule attached to two electrodes. Many factors influence the conductance of single molecule, such as the nature of molecular structure, anchoring groups, and electrode materials. A fine molecule-electrode contacts exhibit efficient charge transportation and high conductance. We measured the conductance of alkanedicarboxylic acids on gold electrodes modified by underpotentially deposited bismuth monolayer. Conductive atomic force microscope and scanning tunneling microscope-based break junction were employed to obtain single-molecule conductance. The conductance measured on gold electrodes modified by underpotentially deposited bismuth monolayer was one order of magnitude lager than that measured on bare Au electrodes. Transition voltage spectroscopy was used to confirm that energy alignment was not influenced by electrodes modified. The higher conductance was induced by great interactions between molecule headgroup and modified electrodes.

並列關鍵字

STM ； molecular electronics

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