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Oxidative Chloride Adsorption and Lead upd on Cu(100): Investigations Into Surfactant-Assisted Epitaxial Growth

Published

Author(s)

Thomas P. Moffat

Abstract

The influence of chloride adsorption and lead upd on the step dynamics of Cu(100) has been examined in acid perchlorate solution. A c(2x2) Cl adlayer is formed upon immersion of a Cu(100) electrode leading to step faceting in the <100> direction. At more negative potentials an order-disorder transformation occurs leading to significant rearrangement of the step. Alternatively, in an electrolyte containing Pb 2+ the halide adlayer may be completely displaced by lead upd. Images of orthogonal surface steps in combination with an assessment of the coulometry suggest that the lead adlayer forms either a highly defective c(2x2), c(5 2 x 2) R45o or a disordered structure corresponding to a coverage ranging from 0.5 to 0.6. The transformation from the halide to the lead adlayer results in the formation of vacancies and adatoms which codense to form holes and islands, respectively. These features may be rationalized by the formation of an alloy phase at low coverage approached 0.5. The morphological consequences of the alloys/dealloying processes are strongly path dependent. Voltammetry reveals that the stripping of the lead upd layer is assoicated with two oxidation waves. As the potential is increased beyond the peak of the first wave the islands disappear which may be due to alloy formation occuring coincident with partial desorption of the lead. The second wave is associated with the nucleation <100>-oriented rows of the c(2x2) cl adlayer which propagate across the terraces displacing the lead phase. The use of metal upd and anions as surfactants in the electrochemical deposition of copper is likely to prove even more interesting than in vacuum deposition since the surfactant coverage and its effect on mesoscopic structure can be continuously manipulated by potential control.
Citation
Journal of Physical Chemistry

Keywords

chloride adsorption, cu (100), lead, oxidative chloride adsorption, STM, surfactant-assisted epitaxial growth, surfactant-assisted growth, underpotential deposition

Citation

Moffat, T. (2008), Oxidative Chloride Adsorption and Lead upd on Cu(100): Investigations Into Surfactant-Assisted Epitaxial Growth, Journal of Physical Chemistry (Accessed April 13, 2024)
Created October 16, 2008