STRUCTURAL TRANSFORMATIONS AT CAF2 SI(111) INTERFACES/

Transformations of the atomic structure of the CaF2/Si(111) interface during annealing have been studied by reflection high energy electron diffraction (RHEED) and X-ray crystal truncation rod (CTR) scattering. The surface morphology after annealing has been studied by atomic for ce microscopy (AFM). A conversion of the epitaxial relation of the fil m with respect to the substrate, from type-A (nonrotated) to type-B (w ith the axes of the film rotated by 180 degrees around the interface n ormal), is monitored by RHEED during annealing of the films. On the ba sis of RHEED, CTR and AFM data, a model of the conversion is suggested . In addition, a spontaneous transition of the type-B interface formed during the growth to the interface with another atomic arrangement ha s been studied with CTR. The possible role of point defect motion in t he CaF2 film during this transition is discussed.