Morphology and Structure of Ultrathin Co- and Au-Films Grown on Ru(0001) Substrates

We have studied the morphology, growth mechanisms, and atomic structure of ultrathin Co- and Au-films on Ru(0001) substrates using Scanning Tunneling Microscopy (STM). During growth at room temperature, kinetic limitations dominate the film morphology rather than thermodynamics. As a consequence, both systems follow a quasi layer-by-layer growth mechanism at room temperature. It proceeds via nucleation and subsequent growth of two-dimensional islands. The crucial role of adatom mobility in island growth is illustrated.