We have performed the first STM study of gallium adsorption on both the Si and C terminated 6H-SiC(0001) surfaces. The development of surface structures was followed as a function Ga coverage. On both the Si-terminated √ x √ and C-terminated 2√ x 2√ surfaces, coverages of less than 1/2 ML resulted in a disordered phase. Increasing the coverage to greater than 1/2, but less than 1 ML produced ordered phases. On the Si-terminated side this consisted of parallel rows of Ga atoms arranged in three different domains, oriented at angles of 120 degrees with respect to each other. Thus the surface symmetry was reduced from three-fold to two-fold. On the C-terminated side, it consisted of interlocking rings of 12 atoms, which appear alternately bright and dark in the STM image. Thus the original threefold symmetry of the SiC surface was preserved. On both surfaces, full monolayer coverage led to the formation of the (1x1)Ga structure
