High-resolution LEED analysis of strained Cu layers on Ru(0001)

Scanning tunnelling microscopic observations have revealed that the relaxation of the lattice strain in the Cu film growing on Ru(0001) occurs in four different stages that are connected with different superstructures depending on the film thickness. Using high-resolution low-energy electron diffraction (HRLEED) the satellite spots of the different superstructures of Cu films with a thickness up to 7 ML (monolayers) grown at 520 K could be identified and quantitatively analysed. However, for Cu films thicker than 2 ML the diffraction patterns are very complex because satellite spots of several superstructures are incoherently superposed. Surprisingly, the structural data derived in a local scale by scanning tunnelling microscopy (STM) are highly representative for the entire surface, analysing by low-energy electron diffraction (LEED). This demonstrates the stability of the relaxation process. Corrugated Cu(111) layers formed after a deposition of 4 ML are rotated with respect to the Ru lattice within a small range of angles of only +/-0.7 degrees. (C) 1997 Elsevier Science B.V.