Competition between terrace and step nucleation: epitaxy of CaF2 on vicinal Si 111/studied by atomic force microscopy

The morphology of CaF2 adlayers deposited on vicinal Si 111.substrates has been studied by atomic force microscopy AFM.for low and high deposition temperatures. In the low temperature regime the adlayer grows in the layer-by-layer growth mode preserving the vicinal step structure of the substrate. The diffusion energy of 1.5 eV for CaF2 molecules on CaF2 terraces is obtained from the transition from terrace to step nucleation. In the high temperature regime the adlayer morphology is very inhomogeneous since the adlayer grows in the Stranski–Krastanov growth mode. Here the CaF2 growing on a closed CaF interface layer does not cover all terraces. This morphology is attributed to the heterogeneous nucleation of islands at steps and to the formation of additional triangular protrusions. q1998 Elsevier Science B.V. All rights reserved.