X-ray scattering study of the surface morphology of Au(111) during Ar+ ion irradiation

Using real-time x-ray scattering to measure the surface morphology of Au(111) during sputter erosion with 500 eV Ar+ ions, we observe three distinct regimes: three-dimensional rough erosion at 20-60 degrees C, quasi-layer-by-layer removal at 120-220 degrees C, and step retraction above 270 degrees C. Sputtering at 20-60 degrees C leads to pattern formation with a characteristic spacing between features. The average separation l between features increases with time t, consistent with a power law l similar to t(0.27+/-0.02). The observations are consistent with the predictions of a continuum model for deposition which includes an Ehrlich-Schwoebel barrier to the interlayer diffusion of surface defects.