Real-time x-ray scattering study of surface morphology evolution during ion erosion and epitaxial growth of Au„111..

We describe a detailed real-time x-ray scattering study of the evolution of the surface morphology of Au~111! both during ion erosion with 500-eV Ar ions, and during homoepitaxial growth. We monitor the erosion and growth morphologies as a function of substrate temperature. We also monitor the surface reconstruction, since it is known to play an important role in determining growth regimes on Pt~111!. Ion irradiation of Au~111! leads to surface morphology evolution by step retraction above 270 °C and quasi-layer-by-layer removal at 90–220 °C. The extent of the surface reconstruction on Au~111! during ion irradiation gradually decreases with decreasing temperature. While the herringbone reconstruction remains during ion irradiation at 270 °C, the long range order is lost and only the ~223)! reconstruction is present at 170 °C. We also observe layer-by-layer growth in the Au/Au~111! system at 55–145 °C, a result that differs from the usual behavior of homoepitaxy on fcc~111! surfaces. As in the layer-by-layer erosion regime, only the ~223)! reconstruction is present during layer-by-layer growth. Room temperature ion irradiation leads to a ~131! surface structure and a three-dimensional rough morphology exhibiting pattern formation with a characteristic lateral length scale. Line-shape analysis of the diffuse scattering in transverse x-ray scans taken during low temperature ion irradiation, indicates that the characteristic lateral length scale increases with time consistent with a power law l;t. This agrees with a simple analysis of the position of the satellite peak in the diffuse scattering in these transverse x-ray scans. @S0163-1829~99!10647-7#