Atomic structure and growth of the Cu/Si(1 1 1)-“5×5” phase

The structure and the growth mode of the Cu/Si(1 1 1)-“5×5” phase have been investigated by low energy electron diffraction and scanning tunneling microscopy by changing annealing temperature for the Cu 2 monolayer (ML) surface deposited on the Si(1 1 1)-7×7 structure. By annealing at 300°C, domains with different lattice spacings and orientations of the “5×5” commensurate structures grow up, and then by annealing at 600°C large domains with irregular unit cells (quasicells) of the incommensurate structure are formed by rotating ±3° against the substrate structure. The “5×5” structure consists of a Cu2Si overlayer with a lattice spacing 10% larger than that of the substrate. In order to relieve the stain energy induced by lattice mismatch, a number of crater defects are produced in the overlayer. The distribution of the crater defects varies depending on annealing temperature. The structure models and the growth mode of the “5×5” phase depending on annealing temperature are presented on the atomic scale and discussed comparing with the results reported in the previous papers.