How the down step edges influence formation of the 7×7 structure

Abstract

A surface that has wide terraces was fabricated by utilizing the step bunching phenomenon to study the effect of the down step edges on the formation of the 7×7 reconstruction. The surface with wide terraces was quenched through the 1×1–7×7 phase transition, freezing the formation process of the 7×7 reconstruction. On this surface, it became possible to investigate the influence of the down step edges on the formation of the 7×7 reconstruction because the influence of the upper step edge, which is located at the other side of the terrace, did not reach to the down step edge. A considerable decrease in the existence probability of the 7×7 reconstruction was observed near the down step edges. This decrease cannot explained by electromigration and steps advancement caused by the difference in adatom density between the 7×7 and disordered structure. Instead, we propose that the decrease in existence probability at down step edges is well explained by a simple topographic model assuming corner holes as the growth nuclei of the 7×7 domains.