Regular arrangement of nanometre-scale clusters by surface strain on stabilized Cl/Si(111)

Abstract

The dynamic processes during halogen etching at a Si(111) surface were observed at atomic resolution using a scanning tunnelling microscope (STM) at high temperature. It was found that after the thermal desorption of chlorine atoms, the metastable ‘1 × 1’ structure and the 7 × 7 structure coexisted at a relatively low temperature. The narrow strips of the metastable ‘1 × 1’ structure within the 7 × 7 structure tended to be straight, presumably because this minimizes the strain energy induced by the reconstruction. At the same time, silicon atoms diffusing on the surface appear to be trapped on the boundary strips, where nucleation occurs to form silicon clusters. After the sample had been cooled to room temperature, the silicon clusters were still regularly aligned. Our results indicate that the dynamics of the reconstruction from the ‘1 × 1’ to the 7 × 7 structure leads to the straightening of the boundary, resulting in the regular alignment of silicon clusters. The formation mechanism of the clusters appears to be related to the stabilization of the surface by halogen adsorption, because such a pattern was not formed upon thermal treatment of Si(111) without chlorine adsorption. The simple thermal treatment presented here may provide a new approach to the assembly of regular arrangements of nanometre-scale silicon clusters.

Nanoscale relaxation in Ru–Si growth on a silicon (111) surface

“…The diffusion of Ru atom (or RuSi x particles) has a lower potential within the disordered regions. With the small energy barrier at high temperatures, migration of the atom or particles occurs easily where the surface disreconstructs into disordered ‘1×1’ from 7×7 . Ru prevents the reconstruction due to termination of the Si dangling bond, and some migrating Si from the outside of the region is absorbed in the Ru‐rich grains.…”