In situ surface x-ray diffraction studies of homoepitaxial growth on Cu(001) from aqueous acidic electrolyte

We present detailed in situ surface x-ray scattering studies of homoepitaxial Cu electrodeposition on Cu(001) electrodes in electrolytes containing chloride and 1 mM or 5 mM Cu(ClO4)2. By time-resolved measurements, insight into the underlying atomic-scale processes is gained up to growth rates of 38 ML/min, revealing a pronounced mutual interaction of the Cl adlayer order and Cu growth behavior. At the lower potential limit, where the Cl adlayer is disordered, step-flow growth is observed. Towards more positive potentials, in the regime of the c(2 × 2) Cl adlayer phase, transitions to layer-by-layer and then 3D growth are found. In turn, the kinetics of the c(2 × 2) Cl adlayer ordering during Cu deposition is substantially slowed down as compared to Cu-free solution. Furthermore, from a detailed analysis of the anti-Bragg peak shape during layer-by-layer growth, an oscillatory average strain in the surface layer is deduced, which is tentatively rationalized by a model considering strain induced by step edges and adatoms.