The surface morphology of reconstructed (001) surfaces was studied by means of scanning tunnelling microscopy following bombardment with 600eV Ar ions to doses ranging from 1013 to 1016/cm2. The results were analyzed in terms of molecular dynamics simulations, using a glue potential. At low doses (5 x 1013/cm2), new defects which were different to the usually observed vacancy islands were detected. They appeared as depressions (0.06nm-deep, 1.44nm-wide). Molecular dynamics simulations, performed using a realistic glue potential which reproduced the hexagonal-like Au(001) reconstruction, confirmed that these depressions were 2-dimensional π/3 dislocation dipoles which originated from the relaxation of vacancy rows on the ridges of the uppermost reconstructed layer. These 2-dimensional dipoles dissociated into individual 2-dimensional dislocations which exhibited the characteristics (glide, climb) of ordinary bulk dislocations. At higher doses (3 x 1014/cm2), vacancy islands which were 1 atomic spacing high nucleated on these depressions. With increasing ion damage, these vacancy islands became the predominant feature. At doses of about 1015/cm2, other defects which were related to the reconstruction - such as perpendicular reconstruction domains and unreconstructed patches of (001) square symmetry - became visible.

Ion Bombardment of Reconstructed Metal Surfaces - from Two-Dimensional Dislocation Dipoles to Vacancy Pits. O.Rodríguez de la Fuente, M.A.González, J.M.Rojo: Physical Review B, 2001, 63[8], 085420 (11pp)