Kinetic Control of CaF 2 on Si(111) Growth Morphology

Thin (0.5 to 8 triple layer) CaF 2 on Si(111) films were grown using molecular beam epitaxy (MBE) and characterized using an in situ combination of x-ray photoelectron spectroscopy (XPS) and componentresolved x-ray photoelectron diffraction (XPD). We identified surface, bulk-like, and interface F and Ca core-level shifts and used the XPS shifts and XPD modulations to identify the growth modes as a function of the kinetic parameters of CaF 2 flux and Si temperature. We identify 3 distinct regimes: (i) for high temperatures and flux we find a complete reacted F-Ca-Si layer, overlaid by 2 layer high islands which coalesce, followed by layer-by-layer growth, (ii) for high temperature and low flux, we find the reacted F-Ca-Si layer to be partially covered with thick islands, and (iii) for low temperatures we find an incompletely occupied F-Ca-Si layer followed by layer-by-layer growth. In all cases we find the buried interface to be structurally identical to the unburied F-Ca-Si layer