Crystallography and Interfaces of Epitaxial Fluorite Metals and Insulators on Semiconductors

Abstract

ABSTRACTCrystals with the cubic fluorite structure and small lattice mismatches can be grown epitaxially on cubic semiconductors. In this manner thin-film single-crystal metals (NiSi2 and CoSi2) and insulators (e.g. CaF2 , BaF2) have been grown on silicon, germanium and indium phosphide. With close attention to deposition and growth parameters, afforded either by atomically clean conditions or transient thermal processing, great control can be exerted over the crystallography and interfaces of these systems. This has resulted in films with unique physical properties and exceptionally high quality and reproducibility. We review the microstructure of these films in this paper and identify two important new growth regimes for these materials: very thin films (less than 30Å) and transient thermal processing with ultra-fast laser pulses. Examination of the structure of these films, using high-resolution electron microscopy, provides insight into these nucleation and growth processes. One intriguing observation is that all these fluorite structure thin films have an overwhelming tendency to grow with a 180° rotated orientation (B) on (111) semiconductors.