Competing processes during the growth on vicinal surfaces are the nucleation on terraces and the nucleation at steps. From kinetic Monte Carlo (KMC) simulations which are performed on vicinal surfaces of various terrace widths, a kinetic phase diagram (parameters: terrace width and deposition temperature) has been deduced. The boundary between both phases of terrace and step nucleation is described by w proportional to rootD(T-c). In addition, the nucleation of CaF on Si(l 1 1) has been investigated by means of scanning tunneling microscopy (STM). A comparison of the experimental data with the kinetic Monte Carlo simulations shows that the diffusion barrier of CaF molecules on Si(l 1 1) is 1.8 eV. (C) 2003 Elsevier Science B.V. All rights reserved.