Role of Step and Terrace Nucleation in Heteroepitaxial Growth Morphology: Growth Kinetics of CaF2/Si(111)

The thickness uniformity and the spatial distribution of lattice relaxation in thin ( $<$8 nm) Ca${\mathrm{F}}_2$/Si(111) films, observed with photoelectron spectroscopy and transmission electron microscopy, are seen to depend strongly on the initial nucleation kinetics. We develop a general model for heteroepitaxial growth that explains both these and literature results. Terrace or step nucleation leads to laminar films, although with different relaxation patterns; combined step and terrace nucleation leads to rough films due to different upper-layer nucleation rates on the differently sized islands.