SPONTANEOUS FORMATION OF AN ORDERED C(4X2)-(2X1) DOMAIN PATTERN ON GE(001)

Scanning-tunneling-microscopy measurements of Ge(001) reveal the prese nce of an ordered domain pattern consisting of c(4X2) and (2X1) domain s arranged in stripes with a width of several dimer row spacings, orie nted along the dimer rows. We suggest that the existence of a soft dom ain wall between the domains combined with a difference in the stress component along the dimer bond for the (2X1) and c(4X2) domains, respe ctively, can conspire to produce such an ordered domain phase. A simpl e model based on strain relaxation explains the observed size of the d omain pattern.