none

• Main Authors: Chao-shan Lai, 賴招珊
• Other Authors: Shueh-lin Yau
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/50407329273461530880

碩士 === 國立中央大學 === 化學學系 === 102 === In situ scanning tunneling microscopy (STM) and cyclic voltammetry (CV) have been used to investigate the adsorption of thiol molecules and its effect on the electrodeposition of copper onto Au(111). First of all, the adsorption of MAA and coadsorption of MAA and copper ions on Au(111) were examined. MAA self-assembled into two order structures, characterized as (3 × √13) and (7 × √3). By contrast, MAA and copper ions were co-deposited via –COO- and Cu2+ coordination in ordered structure with Cu2+ residing in trenches of MAA stripes. For copper deposition on MAA-modified Au(111), MAA admolecules facilitated underpotential deposition (UPD) of copper, which contrasts sharply with the blocking effect observed with typical thiol molecules. In situ STM imaging revealed nucleation of Cu deposit preferentially at surface defects including pits and steps, followed by lateral growth to the entire gold electrode. Meanwhile, a small fraction of gold adatoms aggregated into islands on the Au(111) electrode. At -0.1 V (Ag/AgCl), Cu grew in 3D on the surface, and the islands would coalesce with one another. Bulk Cu deposition produced smooth Cu film onto which MAA molecules segregated into ordered structures. Copper deposition in Cl-containing electrolyte yielded different processes and film morphology. In the initial stage of bulk deposition of Cu film grew in 2D mode, but turned 3D afterward. In situ STM imaging also revealed the copper stripping, which occured at steps firstly. When the Cu deposit was stripped to 3~4 layers thick, a moiré pattern due to MAA admolecules residing on the Cu deposit was observed. Finally, MAA readsorbed on Au(111) when the copper deposite was completely removed. MAA molecules appeared to segregate on the Cu deposite and return to the gold substrate once the Cu deposite was removed in both Cl-free and Cl-containing electrolytes. Lastly, other thiol molecules with different chain length (3-mercaptopropanic acid, MPA and 4-mercaptobutanic acid, MBA) and with different end groups (mercaptopropanesulfonic acid, MPS) were examined. In all cases, surfactant molecules were transferred onto the Cu deposite and returned to the gold electrode once the Cu deposite was stripped off.