Oxidation of preferentially (1 1 1)-oriented Au films in an oxygen plasma investigated by scanning tunneling microscopy and photoelectron spectroscopy

The effect of an oxygen plasma and a consecutive thermal treatment on the chemical state and morphology of a gold(1 1 1) surface has been investigated by photoelectron spectroscopy (XPS, UPS) and scanning tunneling microscopy. An initially atomically flat Au(1 1 1) surface is oxidized to a depth of about 4 nm in an oxygen plasma resulting in a characteristic rough surface morphology. The oxidation of the gold surface can be unequivocally determined from XPS by the chemical shift of the 4f levels. After reduction of such an oxidized gold surface by a thermal treatment, its initial spectroscopic state is completely restored, while the resulting morphology exhibits a pattern of nanometer-sized Au islands.