Scanning tunnelling-microscopic measurements of the (001) surface revealed the presence of an ordered domain pattern which consisted of c(4 x 2) and 2 x 1 domains that were arranged in stripes with a width of several dimer row spacings, and which were oriented along the dimer rows. It was suggested that the existence of a soft domain wall between the domains, combined with a difference in the stress component along the dimer bond for the 2 x 1 and c(4 x 2) domains, respectively, could produce such an ordered domain phase. A simple model, which was based upon strain relaxation, explained the observed size of the domain pattern.

H.J.W.Zandvliet, B.S.Swartzentruber, W.Wulfhekel, B.J.Hattink, B.Poelsema: Physical Review B, 1998, 57[12], R6803-6