Dielectric Properties of Ultrathin CaF2 Ionic Crystals

• DOI: 10.1002/adma.202002525
• Publication Date: 2020-07-15T06:24:50Z
• Authors: Chao Wen; Alexander G. Bans...; Yury Y. Illarionov; Werner Frammelsbe...; Theresia Knobloch; Fei Hui; Nikolai S. Sokolov; Tibor Grasser; Mario Lanza
• Keywords: High-κ dielectric

Abstract Mechanically exfoliated 2D hexagonal boron nitride (h‐BN) is currently the preferred dielectric material to interact with graphene and transition metal dichalcogenides in nanoelectronic devices, as they form a clean van der Waals interface. However, h‐BN has low constant (≈3.9), which ultrascaled devices results high leakage current premature breakdown. Furthermore, synthesis of using scalable methods, such chemical vapor deposition, requires very temperatures (>900 °C) , resulting stacks contain abundant few‐atoms‐wide amorphous regions that decrease its homogeneity strength. Here it shown ultrathin calcium fluoride (CaF 2 ) ionic crystals could be an excellent solution mitigate these problems. By applying >3000 ramped voltage stresses several maps at different locations samples via conductive atomic force microscopy, statistically demonstrated CaF shows much better performance (i.e., homogeneity, current, strength) than SiO TiO h‐BN. The main reason behind this behavior cubic crystalline structure continuous free defects over large regions, prevents formation electrically weak spots.