In Situ STM of 3-Mercaptopropanesulfonate Adsorbed on Pt(111) Electrode and Its Effect on the Electrodeposition of Copper

Abstract

The adsorption of 3-mercaptopropanesulfonate (MPS) molecule on a Pt(111) single-crystal electrode and its effect on the deposition of Cu have been examined using in situ scanning tunneling microscopy (STM). MPS admolecules were irreversibly adsorbed in a largely disordered adlayer on bare Pt(111) in 0.1 M HClO(4), irrespective of the presence of chloride, the concentration of MPS, and the applied potential. In comparison, the MPS admolecules readily formed a highly ordered molecular structure identified as (4x2 root 3)rect on Pt(111) precoated with a monolayer of Cu adatoms. The MPS admolecules were adsorbed upright on Pt(111). The cyclic voltammetric results show that the MPS adlayer on Pt(111) would inhibit Cu deposition because the addition of 10 mu M MPS to the electrolyte of 0.1 M HClO(4)+1 mM KCl+1 mM Cu(ClO(4))(2) reduced the amount of the Cu deposit by half, even in the presence of chloride. The texture of the Cu deposit also varied with the surface state of the Pt(111) electrode as the Cu film grew in three-dimensional islands and smooth flakelike morphology on the MPS-modified and Cu-coated Pt(111) electrodes, respectively. In situ STM results indicated that the MPS admolecules stayed afloat rather than buried by the Cu deposit

Accelerator Screening by Cyclic Voltammetry for Microvia Filling by Copper Electroplating

“…This situation is beneficial for attracting hydrated cations to the cathode because of the formation of an ion pair, which has been confirmed by a scanning tunneling microscopy (STM) study. 53 With respect to the molecular structures shown in Fig. 1, only TBPS, MPS, and SPS contain an SO 3 − end group, whereas MPA and MPO lack this end group.…”

In Situ Scanning Tunneling Microscopy Study of 3-Mercaptopropanesulfonate Adsorbed on Pt(111) and Electrodeposition of Copper in 0.1 M KClO4 + 1 mM HCl (pH 3)

“…Subsequently, MPS could inhibit, rather than accelerate, Cu deposition on Pt(111), as also noted in 0.1 M HClO 4 . 19 We contend that the strength of MPS adsorption on metal electrode could be one of the critical issues here. If it is adsorbed too strongly on a metal such as Pt, its relocation to the top of the Cu deposit would be difficult.…”

“…39 These sorts of Cu deposition were seen with or without MPS in the electrolyte, although 3D growth could begin with smaller overpotentials in the presence of MPS. 19 Because the second Cu layer nucleated before the first Cu layer was completed, the Cu thin film seemed to grow in a pseudo layer-bylayer mode. It is emphasized that the layered type Cu deposition seen in this study was never observed on MPS-modified Pt(111) electrode in 0.1 M HClO 4 .…”

“…It is emphasized that the layered type Cu deposition seen in this study was never observed on MPS-modified Pt(111) electrode in 0.1 M HClO 4 . 19 Higher-resolution STM images were obtained to provide more structural details of the Pt(111) electrode ( Figure 6). The corrugated surface morphology reflects how much Cu adatoms were deposited here.…”

“…23 Rather, we attribute this (3 Â 3) adlattice to MPS admolecules, which gives rise to a (2 Â 2) structure on Pt(111)-supported Cu deposit in 0.1 M HClO 4 . 19 We make it clear that These images were consecutively obtained every 30 s after the potential was switched to 0 V from 0.02 V. Cu deposits were imaged as protruded islands, which grew in size and in density to fill nearly the entire Pt(111) surface within 3 min. All images are 300 Â 300 nm.…”