Preparation of epitaxial ScF$_{3}$ thin films

Scandium trifluoride (ScF$_{3}$) is known for a pronounced negative thermal expansion over a wide range of temperature, from 10 K to 1100 K. The structure of ScF$_{3}$ can be described as an ABX$_{3}$ perovskite with an empty A-site. Related trifluorides have a cubic-to-rhombohedral structural phase transition above room temperature. In contrast ScF$_{3}$ has a cubic structure at all temperatures below its’ high melting point, 1800 K. We have begun to grow ScF$_{3}$ films on oxide substrates using pulsed laser deposition (PLD). There are several unique features to this material that pose challenges for PLD growth: large band gap, non-oxide, poor adhesion under pressure. We have made substantial progress, producing films with a large fraction having very good epitaxy and small mosaic, but remaining regions that are polycrystalline. We update the growth status and initial characterization of ScF$_{3}$ films.