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 the field ion microscope, we have probed in detail the behavior of Ir adatoms at and near the steps of Ir(001) and Ir(111) surfaces. Activation barrier heights of various atomic processes at step boundaries and the atom-trapping strengths of step-edge sites have been measured. These two surfaces exhibit entirely different step properties. At the terrace near the steps of Ir(111), an empty zone of adatom occupation is found 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(111) layers is also derived.