Mapping the Binding Energy of Layered Crystals to Macroscopic Observables

• Published in: Advanced science 2022-11, Vol.9 (33), p.e2204001-n/a
• Main Authors: Moazzami Gudarzi, Mohsen, Aboutalebi, Seyed Hamed
• Format: Article
• Language: English
• Subjects: 2D materials; Approximation; dielectric function; Energy; Equilibrium; graphene; Metals; Optical properties; van der Waals interactions
• ISSN: 2198-3844; 2198-3844
• DOI: 10.1002/advs.202204001

Van der Waals (vdW) integration of two dimensional (2D) crystals into functional heterostructures emerges as a powerful tool to design new materials with fine‐tuned physical properties at an unprecedented precision. The intermolecular forces governing the assembly of vdW heterostructures are investigated by first‐principles models, yet translating the outcome of these models to macroscopic observables in layered crystals is missing. Establishing this connection is, therefore, crucial for ultimately designing advanced materials of choice‐tailoring the composition to functional device properties. Herein, components from both vdW and non‐vdW forces are integrated to build a comprehensive framework that can quantitatively describe the dynamics of these forces in action. Specifically, it is shown that the optical band gap of layered crystals possesses a peculiar ionic character that works as a quantitative indicator of non‐vdW forces. Using these two components, it is then described why only a narrow range of exfoliation energies for this class of materials is observed. These findings unlock the microscopic origin of universal binding energy in layered crystals and provide a general protocol to identify and synthesize new crystals to regulate vdW coupling in the next generation of heterostructures. A framework to probe and quantify binding energies of layered crystals is introduced and this binding energy is mapped to macroscopic observables by analyzing their optical properties with the goal of constructing reliable dielectric functions. Then, a unifying methodology bridging the gap between fundamental characteristics of materials and their binding energies for the entire class of vdW solids, is presented.