Indium adatom diffusion and clustering on stepped copper surfaces.

Abstract

The energetics of indium adatom diffusion and clustering on stepped Cu (001) and (111) surfaces are determined by energy minimization calculations using the embedded-atom method. The terrace substitutional site is found to be energetically favored over adatom and bulk sites in each case, contrary to recent molecular-cluster calculations. Incorporation of indium adatoms into surface substitutional sites by an exchange mechanism is unlikely at low temperatures except at one type of close-packed step on the Cu (111) surface. Condensation of indium adatoms into epitaxial clusters with square and trigonal symmetry at (001) and (111) surfaces, respectively, will occur at low temperatures, while clustering of surface substitutional indium atoms will not. The considerable mobility, and subsequent clustering, of terrace substitutional indium atoms inferred from recent perturbed-angular-correlation experiments utilizing [sup 111]In as a radioactive probe thus conflict with these calculations.