SURFACE STRUCTURES AND GROWTH MODES FOR Cu ON Si(100), (110) AND (111) SURFACES DEPENDING ON Cu SEGREGATION BY HEAT TREATMENT

Cu has a large diffusion coefficient in Si, like Ni, and hence the deposited Cu atoms on the Si clean surfaces diffuse into the bulk with increasing temperature and segregate to the surface by quenching. Thus, the surface reconstructed structure changes by heat treatment depending on the surface Cu concentration induced by heat treatment. Moreover, the quantity of Cu segregation decreases with increasing annealing time, because the diffused Cu atoms are trapped to islands on the surface while annealing. The quantity of diffusing Cu atoms into the bulk and the desorption temperatures of Cu from the reconstructed surfaces depend on the crystallographic orientations of the substrate surface. Different cohesive energies of the surface superstructures and different temperatures of the Cu segregation depending on surface orientations are discussed based on the structures on Cu–Si layers formed on the Si (100), (110) and (111) surfaces.