Low-temperature interface structure of CaF2/Si(111) studied by combining x-ray standing waves with component-resolved photoemission -: art. no. 193404

X-ray photoelectrons excited by x-ray standing waves (XSW) are used to study the atomic structure of the low-formation-temperature (370degreesC) interface between CaF2 and Si(111). The core-level shift of the photoemission spectra of the Ca atoms at the CaF2/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 CaF2/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 CaF2 films consist of domains with type-A and type-B orientation.