STM-INDUCED FORMATION OF AG ISLANDS ON AG(111)

The formation of triangular-shaped adatom islands and vacancy islands on Ag(111) at room temperature is observed in a local growth experimen t. The tip of a scanning tunneling microscope (STM) vibrating normal t o the surface leads to a local modification. Atoms are removed from fl at terraces and renucleate as adatom islands. Simultaneously with the modification process the surface is imaged with the STM. In the case o f triangular islands only one out of two possible types of close-packe d [110] step edges is found in the STM images. This observation is exp lained by differences in the step formation energy, rather than by dif fusion.