本研究藉由循環伏安法(cyclic voltammetry, CV)分析MPS單分子膜在電極表面的電化學行為，並利用電化學式掃描電子穿隧顯微鏡(electrochemical scanning tunneling microscopy, EC-STM)，觀察其吸附結構，並即時記錄MPS於金(111)載體表面的脫附行為。實驗結果顯示，MPS單分子膜穩定存在於電雙層的電位區間為0.11V～0.8V。在電位比0.11V正時，MPS單分子膜會行氧化吸附反應，而電位比0.06V負時，MPS單分子膜會行還原脫附反應。由EC-STM更發現，MPS單分子膜在0.8V～0.6V電位區間具有二維規則結構，其規則結構為(√21 × 2√19)。
由循環伏安法分析，經過MPS單分子膜修飾後的金(111)電極，改變銅低電位沉積的現象由典型蜂巢結構(√3 × √3)轉變為(1 × 1)結構相轉移峰消失，顯示MPS能夠改變銅沉積於金(111)的型態，且銅沉積量減少20%，表示MPS的存在對銅沉積呈現抑制的作用。由EC-STM觀察，金(111)電極經過MPS分子修飾後，於0.6V時銅的UPD行為以零星島狀物方式呈現。同時出現具有(4 × √13)規則結構的MPS單分子膜。此單分子膜的存在抑制銅沉積，使銅覆蓋率由0.33ML降低至0.1ML。而當電鍍液中含有氯離子時，銅的UPD電位由0.6V往正電位偏移至0.68V，且成長模式變為二維方向的層狀沉積方式。此外，由於氯離子與MPS共存，MPS單分子膜形成有別於(4 × √13)的霧狀不規則結構。In-situ STM更指出，僅有霧狀分子膜存在的區域能觀察到銅島狀物沉積。因此MPS單分子膜改變銅沉積型態與抑制銅沉積的作用，可由CV及STM得到證實。

Copper deposition on Au(111) electrodes in aqueous sulfuric acid solution is an important model system which has been extensively studied. To improve the quality of electrodeposited films, additives, such as 3-Mercapto-1-propansulfonic acid (MPS) and chloride ions, are commonly employed in industrial plating bathes. Electrochemical scanning tunneling microscopy (EC-STM) and cyclic voltammetry (CV) were used to study the adsorption of MPS on Au(111) electrodes and the behavior of MPS desorption. STM images revealed an ordered (√21 毕 2√19) MPS adlayer at potentials >0.6V and a disordered phase at more cathodic potentials. Measurements revealed that MPS monolayer is stable in the electric double-layer at the potential between 0.11V to 0.8V.
In Cu containing electrolytes, cathodic peak of Cu underpotential deposition (UPD), corresponding to (√3 毕 √3) transferred to (1 毕 1) is disappeared. In analog STM experiments, the MPS adlayer is (4 × √13) ordered structure in the position where no Cu deposition takes place.
An additional amount of 1.4 mM chloride ions strongly affects the growth behavior of Cu UPD. Cu islands deposit in the region with the 库 phase. A two-dimensional growth of monoatomic height Cu islands forms the Cu UPD layer. Coalescence of the islands at the higher coverage results in a connected layer with fractal shape.

Keywords: Self-assembly monolayer, scanning tunneling microscopy, electrochemical copper deposition

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