Effect of atomic structure at epitaxial CaF sub 2/Si(111) interface on electrical properties.

High resolution electron microscopy has been used to determine the atomic structure at the epitaxial CaF sub 2/Si(111) interface before and after a rapid thermal anneal. Direct Ca-Si bonding at the interface, with 8-fold coordinated Ca atoms is observed in as-grown layers. Fluorine is preferentially removed from the interface during a rapid thermal anneal leaving 5-fold coordinated Ca atoms. A dramatic improvement in the electrical properties of the interface is observed after annealing.