Arrays of widely spaced atomic steps on Si(111) mesas due to sublimation

摘要

Steps with spacings of microns form on top of mesas fabricated on Si(111)that is annealed at temperatures where sublimation becomes important. Uponannealing, mesas first develop ridges along their edges, effectively creatingcraters which then become step-free by a step flow process described in theliterature. Due to the miscut of the average surface from (111), ridgebreakdown occurs on one edge of each mesa as sublimation proceeds. Thebreakdown point then acts as a source of steps which spread out over the mesasurface. The distribution of steps in the resulting step train depends on thesublimation rate, direct step-step interaction and the diffusive exchange ofatoms among the steps. Computer simulations using BCF (Burton, Cabrera andFrank) theory provide insight into the controlling processes. The resultssuggest that self-organization of the wide terrace distributions in the lowstep density area occurs under sublimation. We compare the experimental andpredicted step distributions.