“…GaAs(0 0 1) was the first electrode surface of a semiconductor to be studied in situ by X-rays in contact with an electrolyte (under potential control) [17]. At anodic potentials, the corrosive process could be in situ observed, rendering the surface increasingly rough, whereas at negative potentials, the roughness of the surface could be slightly decreased, which could be attributed to the process of preferentially etching of the As by the nascent atomic hydrogen [17,18].…”