Time-resolved grazing incidence small-angle X-ray scattering and atomic force microscope studies were made of the evolution of the surface morphology of the Co(00•1) surface during low-energy Ar+ ion sputtering. Above 573K, the surface was smooth, with erosion proceeding in either a layer-by-layer mode or a step-retraction mode. Below 573K, the surface developed a correlated pattern of mounds and/or pits with a characteristic length scale, λ. At room temperature, the surface morphology was dominated by mounds, and coarsened as time progressed. The characteristic length scale obeyed the apparent power law, λ = A x tn with n = 0.20. The rms roughness of the surface increased in time according to a similar power law with a slightly larger exponent β = 0.28. Kinetic Monte Carlo simulations of a simple model of Cu(111) were also performed. These simulations suggested that mound formation and coarsening at low temperatures was due to the slow diffusion of sputter-created adatoms on step edges. The morphological transition from mounds to pits was associated with activation of kink diffusion. These simple simulations produce values for the scaling exponents that agree with the experimental measurement.

Ion-Induced Pattern Formation on Co Surfaces: an X-Ray Scattering and Kinetic Monte Carlo Study. O.Malis, J.D.Brock, R.L.Headrick, M.S.Yi, J.M.Pomeroy: Physical Review B, 2002, 66[3], 035408