Manifestation of twofold anisotropic domain growth kinetics on fourfold substrates

Strongly anisotropic domain growth is observed during phase segregation of a 2-dimensional silicide on Cu(001). At saturation, two degenerate orthogonal domains interlock to fill the surface. As diffraction methods show fourfold symmetric superlattice peaks, real space imaging and a novel sitewise counting procedure are used to verify the presence of metastable anisotropic domain configurations. Comparison of the domain configurations with space filling simulations confirms anisotropic growth in a system within the X-Y universality class with cubic anisotropy.