Bulk crystalline copper electrodeposited on polycrystalline gold surfaces observed by in-situ scanning tunnelling microscopy

Bulk copper electrodeposition onto technical gold surfaces in electrolytes of 0.05 M H₂SO₄ and 1 mM CuSO₄ was investigated by in-situ scanning tunnelling microscopy at fixed overpotentials. At potentials between -60 and -30 mV the growth of bulk copper proceeds in cycles of nucleation, agglomeration and crystallization. Crystalline copper is seen as involving an intermediate stage in the progress of growth. The final stage in the growth involves an equilibrium of copper electrochemically dissolving and precipitating. The drift velocity was measured for a gold surface subjected to flame annealing and subsequently installed in the cell compartment. It was found that the drift velocity decays with time in an exponential-like manner, and a 70 min waiting time before experiments with atomic resolution is recommended. Atomic resolution on Au(111) has been obtained, and an apparent surface reconstruction was observed. It is suggested that in reality no reconstruction took place, and that the observation was due to a distortion of the image caused by a constant drift velocity. A mathematical expression which relates the observed surface structure to the drift velocity is presented.