Mechanisms for annealing of ion-bombardment-induced defects on Pt(111)

The morphology of a Pt(111) crystal during bombardment with 600-eV Ar⁺ ions has been investigated at constant temperatures Tₛ with thermal-energy atom scattering. Below Tₛ{}600 K the formation of three-dimensional (3D) structures is observed, while above Tₛ{}700 K the removal proceeds layer by layer. From the quantitative modeling of the data we infer that 3D structures develop when annealing proceeds only by intralayer diffusion of vacancies, while layer-by-layer removal is observed when interlayer mass transport also becomes effective. The latter process is believed to be related to the onset of meandering (roughening) of atomic steps.