GROWTH OF ULTRATHIN FILMS OF COPPER ONTO ALPHA-AL2O3(0001) - MECHANISM AND EPITAXY

The growth of an ultrathin film of copper on an alpha-Al2O3(0001) surface was studied by Auger and electron energy-loss spectroscopy and by low-energy electron diffraction. From Auger results it is indicated that atomic-layer metal-beam deposited copper grows in the Stranski-Krastanov mode at room temperature upon a substrate that was pre-annealed in air followed by a cool-down process in a nitrogen-water vapour mixture. At average copper deposition thicknesses below 2 angstrom a chemical bond was established between copper and the substrate, and the low energy-loss data suggests an initial formation of Cu(I) states on the substrate. On heating, an agglomeration of the copper was found for thicknesses above 2 angstrom of copper. On further deposition, followed by a heat treatment, copper grows epitaxially as Cu(111)R30-degrees parallel-to (1 x 1)alpha-Al2O3(0001).