COMBINED X-RAY AND STM STUDY OF THE OXYGEN-INDUCED RESTRUCTURING OF THE AU(111) SURFACE

Au(111) surfaces exposed to oxygen under high pressure (po(2) = 1 bar) and at high temperature (T approximate to 800 degrees C) during an ex tended period of time (several hours) exhibit a (root 3 x root 3)R30 d egrees structure and, at larger scales (a few nanometers), a long rang e hexagonal height modulation with a period of 72 Angstrom. This is ev idenced by X-ray diffraction at grazing incidence performed at the ESR F. These results confirm and complete previous surface analysis in dir ect space by scanning tunneling microscopy (STM). This new evidence fo r a long range superstructure by X-ray diffraction provides new insigh ts into the origin of the moire patterns observed in the STM study.