$In situ$ and in real time electrochemical-stm analysis of sulphate adsorption on vicinal Cu(111) electrode surfaces.

Copper has been termed the "metal of the 21st century". The electrochemical production of integrated copper circuitry has revolutionized information technology. The decreasing dimension of the circuitry wires and vias calls for a detailed understanding of the electrochemical behaviour of copper on the nanometer, even atomic, scale. This turns the gaze on the influence of atomic scale surface defects in the electrochemical deposition and etching processes. In this contribution we present $in situ$ electrochemical scanning tunnelling microscopy results on the reconstruction of well-defined vicinal Cu(111) electrodes of progressively reduced terrace width ($e.g.$, Cu(21 21 16) and Cu(221)) in dilute sulfuric acid solution ($H_{2}SO_{4}$). In contact with $H_{2}SO_{4}$ the flat reference Cu(111) electrode is known to reconstruct in a stable Moiré superstructure. At the potential for which bare Cu(221) is expected, the surface appears directly covered by some regular stripes, forming three ensembles of the Cu(221) terraces ({1.2 $nm$; 2.1 ${nm}$ and $3.3 {nm}$). All three widths are significantly larger than the bare Cu(221) terrace ({0.74 ${nm}$) but fully consistent with multiples of the size of a Moiré unit.