Calcium fluoride as high-k dielectric for 2D electronics

Calcium fluoride is a dielectric material with a wide bandgap (∼12.1 eV) and a relatively high dielectric constant (∼6.8) that forms a van der Waals interface with two-dimensional (2D) materials, meaning that it contains a very low amount of defects. Thin calcium fluoride films can be synthesized using multiple techniques that are scalable to the wafer level, including molecular beam epitaxy, atomic layer deposition, and chemical vapor deposition. However, the consolidation of calcium fluoride as dielectric for 2D electronics requires overcoming some fundamental challenges related to material quality and integration, as well as carrying out advanced characterization and computational studies to evaluate its real potential. Here, we review the status of calcium fluoride dielectric films in terms of material synthesis, fundamental electrical properties, and future applications; we also discuss the most important challenges of calcium fluoride integration in 2D materials–based, solid-state nano/micro-electronic devices, and propose several potential routes to overcome them. Our manuscript may serve as a useful guide for other scientists working on 2D electronics in general, and provides a clear pathway for calcium fluoride research in the future.