COOPERATIVE SEGREGATION OF BORON AT SI(111)

Interface segregation of boron at Si(111) surfaces has been studied at the atomic scale using a scanning tunnelling microscope (STM). During the segregation process (produced by thermal annealing), strong coope rative effects take place which cannot be explained by a simple neares t-neighbour pair interaction model. Although average surface concentra tions of boron in the investigated temperature range could be calculat ed in terms of a Fowler's model, the comparison between STM and simula ted images suggests that one must introduce longer-range interactions to describe the atomic-scale configurations.