Temperature dependence of the sputtering morphology of Pt(111)

The morphology of the Pt(111) surface after sputtering with 600 eV Ar+ ions as a function of the annealing temperature, during and after sputtering, has been investigated by scanning tunneling microscopy. The data confirm the transition from pit formation to layer-by-layer removal regime and emphasize the role of thermally created adatoms and/or vacancies in the mass transport between atomic layers. The measurements show further that the shape of the vacancy islands upon annealing above 700 K is equilibrium-like. The application of the Wulff construction to the two-dimensional vacancy islands allows the determination of the ratio of the free energies of the two types of step edges which bound the islands.