ENERGETICS OF SURFACE ATOMIC PROCESSES NEAR A LATTICE STEP

An atomic step of a solid surface can act as not only a reflective or nonreflective boundary but also as an atom-trapping boundary. Using th e field ion microscope, we have probed in detail the behavior of Ir ad atoms at and near the steps of Ir(001) and Ir(lll) surfaces. Activatio n barrier heights of various atomic processes at step boundaries and t he atom-trapping strengths of step-edge sites have been measured. Thes e two surfaces exhibit entirely different step properties. At the terr ace near the steps of Ir(lll), an empty zone of adatom occupation is f ound the width of which depends on the terrace size. The difference in the reflective barrier heights of A-type and B-type step edges of Ir( lll) layers is also derived.