V AND CR ON RU SURFACES

By molecular beam epitaxy (MBE) we have prepared (0001)-hcp Ru films o n SrTiO3(111), Al2O3(0001) and Al2O3(11(2) over bar 0) surfaces. Refle ction high-energy electron diffraction (RHEED) intensity oscillations are observed during the growth of the Ru films, up to temperatures of 870 K. Despite that, we found that high substrate temperatures are req uired for the initial deposition of Ru. Scanning tunnelling microscopy (STM) investigations show monoatomic terraces of up to 100 nm in widt h, and atomic resolution on Ru, although the imaging was performed und er ambient conditions. The high crystallinity of the Ru films is prove n by RHEED and by the appearance of interference fringes in the peak p rofiles of high-angle X-ray diffraction patterns. V and Cr grow pseudo morphic on Ru in the layer-by-layer growth mode for the first few mono layers (ML), afterwards island growth is obtained. In-plane lattice pa rameter measurements performed during the growth of the V films at roo m temperature show a rather slow relaxation with the first 10-15 ML to the bulk bcc value, in contrast to Cr films. (C) 1998 Elsevier Scienc e B.V.