Copper deposition on metal electrodes modified by organosulfur compounds has been extensively studied, from which some fundamental insights of this indispensable process used for semiconductor packaging have been obtained. This study employs voltammetry and scanning tunneling microscopy (STM) to examine Cu deposition on Pt(111) electrode modified with mercaptoacetic (MAA) and mercaptopropionic acids (MPA) in 0.1 M sulfuric acid containing 10−5 M CuSO4. The slight difference in the molecular structures of these organic surfactants leads to stark differences in Cu deposition. Both electrochemical and STM results show that Cu deposition proceeds much faster at the MAA- than MPA-modified Pt(111) electrode. Bulk Cu deposit grows in layers and 3D crystallites on the MAA- and MPA-modified Pt(111) electrodes, respectively. STM imaging shows that MAA and MPA modifiers segregate from the Pt(111) electrode to the Cu deposit, arranging in (√3 × √3)R30° like structures after Cu UPD, and transforming to Moire and striped patterns for bulk Cu deposition. Although MAA and MPA adsorbed on Pt(111) are both hydrogen-bonded to their neighbors, the latter has a higher degree of freedom to orient on the electrode for more intermolecular hydrogen bonds, which decreases the interaction between –COOH and Cu2+ and finally causes slower Cu deposition.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry