Vacancy line defects on the (001) surface, which were induced by traces of Ni, were analyzed by means of scanning tunnelling microscopy. It was found that the domain structure which was found obeyed a size relationship which had been derived for surface systems with long-range interactions that decayed in inverse-square manner. From the thermally-induced wandering of the vacancy line defects, the strength of the long-range repulsive interaction was deduced, as well as the short-range attractive interaction between vacancies in adjacent dimer rows.

H.J.W.Zandvliet, H.K.Louwsma, P.E.Hegeman, B.Poelsema: Physical Review Letters, 1995, 75[21], 3890-3