Surface chemical shifts and photoelectron diffraction in CoSi2

Abstract

An angle resolved study of the Si(2p) photoelectron line from bulk-grown CoSi2(111), (100), and (110) surfaces has been performed using synchrotron radiation. A surface shifted component has been observed from annealed (111) and (100) faces, the surface/bulk intensity ratio being a strongly modulated function of polar emission angle and of photoelectron kinetic energy. Surface emission has been found to be significantly stronger from (111) faces than from (100) faces. We adopt a model in which the (100) face is terminated in a single Si layer, whereas we suggest that in the (111) surface, two Si layers exist above the first layer of Co atoms, thereby forming a Si (111)-like template for the further growth of epitaxial Si. We consider that the interfacial Co atoms are sevenfold coordinated. Fractured CoSi2(111) surfaces are found to exhibit no surface Si.