Copper clusters on Al2O3/NiAl(110) studied with STM

The structure of nanosize Cu clusters has been studied with scanning tunnelling microscopy (STM). The clusters were deposited on a thin aluminium oxide film created by oxidation of NiAl(110). The STM images show that the Cu grows as 3D islands on the Al2O3 film, for the coverages studied (theta (Cu) less than or equal to 5 ML). For crystalline clusters larger than similar to 40 Angstrom, the top facet could be imaged with atomic resolution, revealing a (111) facet. From the shape of the crystalline clusters information about the Cu surface energies has been extracted and compared to theoretical values. From the height-to-width ratio of the Cu clusters the work of adhesion for Cu on the Al2O3 film could be determined to be 2.8 +/- 0.2 J/m(2) using theoretical values for the surface energies. (C) 2001 Elsevier Science B.V. All rights reserved.