HIGH-RESOLUTION LEED ANALYSIS OF STRAINED CU LAYERS ON RU(0001)

Scanning tunnelling microscopic observations have revealed that the re laxation of the lattice strain in the Cu film growing on Ru(0001) occu rs in four different stages that are connected with different superstr uctures depending on the film thickness. Using high-resolution low-ene rgy 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. Howeve r, for Cu films thicker than 2 ML the diffraction patterns are very co mplex because satellite spots of several superstructures are incoheren tly superposed. Surprisingly, the structural data derived in a local s cale 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. Cor rugated Cu(111) layers formed after a deposition of 4 ML are rotated w ith respect to the Ru lattice within a small range of angles of only /-0.7 degrees. (C) 1997 Elsevier Science B.V.