Photoelectron diffraction for the sulfur interlayer between CaF2 epitaxial layers and sulfur-passivated InP(100)

We report here the structural analysis with X-ray photoelectron diffraction (XPED) on the interface between CaF2 epitaxial layers and a sulfur-passivated InP(100) surface. Multiple-scattering cluster calculations with spherical-wave scattering (MSC-SW) give a good description of the XPED from both the InP(100) substrate and the CaF2 overlayer and show that CaF2 grows epitaxially on the substrate as CaF2(100) islands even at the initial stages of epitaxy. On the other hand, forward scattering peaks are observed in angular distributions of S2p intensities, which indicate the directions of the interatomic axes between S and Ca and/or F at the interface. We determined the possible stacking of CaF2 layers on the S interlayer from these results and MSC calculations.