The dynamic processes during halogen etching at a Si(111) surface were observed at atomic resolution using a scanning tunnelling microscope at high temperature. It was found that after the thermal desorption of chlorine atoms, the metastable ‘1 x 1’ structure and the 7 x 7 structure coexisted at a relatively low temperature. The narrow strips of the metastable ‘1 x 1’ structure within the 7 x 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 occurred to form silicon clusters. After the sample had been cooled to room temperature, the silicon clusters were still regularly aligned. The results indicated that the dynamics of the reconstruction from the ‘1 x 1’ to the 7 x 7 structure led to straightening of the boundary; resulting in the regular alignment of silicon clusters. The formation mechanism of the clusters appeared 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 was suggested to provide a new approach to the assembly of regular arrangements of nm-scale silicon clusters.

Regular Arrangement of Nanometre-Scale Clusters by Surface Strain on Stabilized Cl/Si(111). K.Shudo, Y.Koike, Y.Owa, M.Koma, S.Ohno, M.Tanaka: Journal of Physics - Condensed Matter, 2007, 19[9], 096010 (10pp)