Low-temperature interface structure ofCaF2/Si(111)studied by combining x-ray standing waves with component-resolved photoemission

Abstract

X-ray photoelectrons excited by x-ray standing waves (XSW) are used to study the atomic structure of the low-formation-temperature (370°C) interface between CaF 2 and Si(111). The core-level shift of the photoemission spectra of the Ca atoms at the CaF 2 /Si interface is used to distinguish interface Ca atoms from atoms in other (bulk) layers in the XSW measurements. Therefore, we obtained quantitative structure information specific to the buried CaF 2 /Si interface avoiding some of the ambiguities of XSW. Even at the low growth temperatures used here, the interface is well ordered, with interface Ca atoms exclusively adsorbed on T 4 sites. The majority of the interface layer has CaF stoichiometry. The CaF 2 films consist of domains with type-A and type-B orientation.