利用掃描式電子穿隧顯微鏡觀察硫醇分子對於銅沉積在鉑(111)電極上的影響

Cu electrodeposition on thiol-modified Pt(111) and UPD Cu/Pt(111) single crystal electrodes as probed by EC-STM

杜欣霖(Hsin-Ling Tu)

指導教授 ： 姚學麟

國立中央大學/理學院/化學系/碩士(2011年)

摘要

掃描式電子穿隧顯微鏡（in situ scanning tunneling microscopy，STM）和循環伏安法（cyclic voltammetry，CV）分別觀察3-巰基丙烷磺酸鈉鹽（3-Mercapto-1-propanesulfonic acid sodium salt，MPS）與聚二硫二丙烷磺酸鈉（bis-3-sodiumsulfopropyldisulfide，SPS）在0.1 M過氯酸水溶液下對於電鍍銅的影響。由STM的結果可得知當溶液中只含有銅及氯時，銅沉積於Pt(111)電極表面時會以層狀方式成長；若Pt(111)先修飾MPS分子或SPS分子時，銅沉積的過程則會變成以破碎的方式成長且易形成島狀物，且從CV的結果可得知，銅沉積是被抑制的。當鉑(111)電極表面先沉積UPD銅膜後再以MPS分子修飾，進行OPD銅的沉積，發現其沉積不在是全面且均勻的方式，而是以小面積，形狀為雪花狀形式沉積於電極表面上，且3維的沉積速度＞2維的沉積速度。沉積過程中可在UPD銅上觀察到MPS與氯共吸附的結果所形成的（4 × 2√3）整齊結構排列，在厚銅層（約2層以上）時則可觀察到（2 × 2）的整齊MPS分子吸附結構。將MPS改為SPS時，於第一階段的UPD銅沉積完後加入SPS分子，可發現，面上出現大小不一的缺陷，從CV的結構可證明，缺陷是來個於鉑(111)電極表面的銅被SPS置換後所得到的結果。當於第二階段的UPD銅沉積完後加入SPS分子，SPS分子會以（4 × 4）的結構吸附於氯/UPD銅/鉑(111)上。當電位往負調整時，同樣地可於第二層銅上觀察到SPS分子的吸附情況，在此階段的SPS分子吸附會使得表面的銅原子層產生重排的現象，從六方排列轉變為四方排列。再繼續往負調整，亦可發現，此一造成重排結構於第三層銅以上時便轉變為（2 × 2）與結果與MPS吸附於厚層銅上的結構相符。
由循環伏安法（CV）之結果得知，銅、氯、MPS分子或SPS分子三種物質必須在某一特定比例下才會有最佳的增進銅沉積之效果。且MPS分子或SPS分子必須是吸附於銅上才會具有明顯的增進現象；若MPS分子或SPS分子吸附於鉑(111)電極上時，對於銅沉積則是有抑制的效果。

關鍵字

加速劑 ； 銅製程 ； 無電電鍍

並列摘要

In situ scanning tunneling microscopy (STM) and cyclic voltammetry (CV) have been used to examine the effect of 3-mercaptopropanesulfonate (MPS) and bis-3-sodiumsulfopropyldi-sulfide (SPS) on the electrodeposition of copper onto a well-ordered single crystalline electrodes of Pt(111) in 0.1 M HClO4. In situ STM imaging reveals atomically flat surface morphology of copper films deposited on ordered Pt(111) electrode, implying layer-by-layer growth mode of Cu in 0.1 M HClO4 + 1 mM Cu(ClO4)2 + 1 mM KCl. However, it implied islands growth mode of Cu with MPS or SPS-modified Pt(111). The MPS or SPS admolecules were adsorbed upright on Pt(111). The cyclic voltammetric results show that the MPS or SPS adlayer on Pt(111) would inhibit Cu deposition because the addition of MPS or SPS to the electrolyte of 0.1 M HClO4 + 1 mM KCl + 1 mM Cu(ClO4)2 reduced the amount of the Cu deposit, even in the presence of chloride.
For MPS-modified and Cu-coated Pt(111) electrodes system, Cu film grew in smooth flakelike morphology. The deposition rate is 3D > 2D. The MPS admolecules readily formed a highly ordered molecular structure identified as (4 ×2 √3)rect on Pt(111) precoated with a monolayer of Cu adatoms and a ordered structure identified as (2 ×2) on thicker layers of Cu adatoms.
For SPS-modified and Cu-coated Pt(111) electrodes system, Cu film also grew in flakelike morphology. But the processes of SPS adsorption varied greatly with the structures of the electrified interface of Pt(111) at 0.4 and 0.2 V (vs. Ag/AgCl), where Cu adatoms and chloride anions were coadsorbed in highly ordered arrays. The Cu-coated Pt(111) electrode was then exposed to a dosing solution containing SPS. In situ STM imaging revealed that the (4 × 4) - Cu + Cl bidlayer produced at 0.4 V was completely displaced by SPS molecules, resulting in MPS molecules adsorbed randomly on the Pt(111) electrode and cupric cations dissolving in the electrolyte. Incontrast, the Pt(111) - (√7 × √7)R19.1°–Cu + Cl structure produced at 0.2 V wasstable against the subsequently deposited SPS molecules, yielding locally ordered (4 × 4) –SPS structures residing on the Cu + Cl bilayer. With an overpotential η< 100 mV, bulk Cu deposition proceeded slowly and built up the Cu film in layers. Each Cu layer appeared to be atomically smooth and arranged in an ordered structure. Intriguingly, the second Cu layer was unique, because it adapted a square-like lattice, tentatively attributed to MPS molecules residing atop a pseudo Cu(100) network. As the Cu deposit thickened, in situ STM revealed a (2 × 2) structure, attributable to MPS admolecules sitting on a hexagonal Cu(111) lattice. MPS molecules could be produced by the reduction of SPS.
Copper, chloride and MPS or SPS all need to be in a specific ratio and MPS or SPS-modified on Cu-coated Pt(111) electrode so that could accelerate Cu deposition. If MPS or SPS modified on Pt(111) even if at the specific ratio, the result will be inhibited the Cu deposition.

並列關鍵字

SPS ； MPS ； STM ； copper deposition

參考文獻

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