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(1 1 1) substra tes has been studied by atomic force microscopy (AFM) for low and high deposition temperatures. In the low temperature regime the adlayer gr ows in the layer-by-layer growth mode preserving the vicinal step stru cture of the substrate. The diffusion energy of 1.5 eV for CaF2 molecu les on CaF2 terraces is obtained from the transition from terrace to s tep nucleation. In the high temperature regime the adlayer morphology is very inhomogeneous since the adlayer grows in the Stranski-Krastano v growth mode. Here the CaF2 growing on a closed CaF interface layer d oes not cover all terraces. This morphology is attributed to the heter ogeneous nucleation of islands at steps and to the formation of additi onal triangular protrusions. (C) 1998 Elsevier Science B.V. All rights reserved.