X-Ray Scattering Study of the Surface Morphology of Au(111) duringAr+Ion Irradiation

Using real-time x-ray scattering to measure the surface morphology of Au(111) during sputter erosion with 500 eV ${\mathrm{Ar}}^{+}$ ions, we observe three distinct regimes: three-dimensional rough erosion at 20– $60°\mathrm{C}$, quasi-layer-by-layer removal at 120– $220°\mathrm{C}$, and step retraction above $270°\mathrm{C}$. Sputtering at 20– $60°\mathrm{C}$ 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 $l\sim t^{0.27\pm 0.02}$. 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.