He scattering study of Au(111) nanostructured by ion sputtering

The morphology of the (111) surface of gold induced by ion sputtering has been investigated in the temperature range between 190 and 400 K using thermal energy He atom scattering with a beam energy around 3 meV. After sputtering at grazing incidence (about 75 degrees) along the azimuthal direction < 110 > and at crystal temperature in a range 160-260 K, a well defined ripple structure with ridges oriented along the incoming ion beam direction has been observed. In fact the diffraction pattern in the same direction shows a sharp specular peak while in the 90 degrees direction the pattern shows a specular peak with two satellites around 0.03 angstrom(-1). The evolution with time of this structure has been followed at different crystal temperatures T-C in the range 300-400 K to gain information on ripple stability and on the diffusion processes contributing to ripple decay. Preliminary results show that up to 350 K the diffraction pattern does not show appreciable changes at least for 24 hours. Instead for T-C >= 370 K the intensity of satellite peaks decreases with a rate which depends on temperature. At 400 K the satellite peaks disappear within I hour while at 370 K they survive at least for 6 hours.