Potential dependence of decay rate of multi-layered islands on Au(1 0 0) single crystals in sulfuric acid solution

We have investigated the decay of multi-layered islands on Au(1 0 0) single crystals and the potential dependence in 0.05 M H2SO4 aqueous solution at room temperature by in situ EC-AFM. The initial shape of each layer of the islands is a square or a octagon and it is found that these layers are mainly surrounded by 〈0 1 1〉; the step edges with high atomic density. The number of atoms in the first layer decreases linearly with time, suggesting that the detachment of the atoms from the island is a limiting process of the decay. The decay rate of the second or third layer after the complete collapse of the upper layer is almost the same as that of the first layer and it is much faster than that after the complete collapse of the upper layer. This result suggests that the current of atoms from the upper layer to the second or third layer results in the supersaturation of atoms on the terrace near the step edge. When the potential of Au(1 0 0) increases in the potential range between 0.15 and 1.2 V, the decay of the island becomes faster. We concluded that an increase of the electrostatic free energy at step edge increases the current of atoms from the island in contact with electrolyte. The decay rate of the holes created by the AFM cantilever is approximately an order of magnitude smaller than that of the first layer of the islands.