High-refractive index and mechanically cleavable non-van der Waals InGaS3

TL;DR

This paper investigates ultrathin non-van der Waals InGaS3 sheets, revealing their unique covalent bonding, layered structure, wide bandgap, high refractive index, and potential for nanophotonics applications.

Contribution

It provides the first detailed analysis of the optostructural properties of mechanically cleaved InGaS3, highlighting its covalent bonds and optical suitability for nanophotonics.

Findings

Layer isolation energy ~50 meV/Ų comparable to van der Waals materials

Wide bandgap of 2.73 eV with high refractive index over 2.5

Negligible optical losses in visible and infrared ranges

Abstract

The growing families of two-dimensional crystals derived from naturally occurring van der Waals materials offer an unprecedented platform to investigate elusive physical phenomena and could be of use in a diverse range of devices. Of particular interest are recently reported atomic sheets of non-van der Waals materials, which could allow a better comprehension of the nature of structural bonds and increase the functionality of prospective heterostructures. Here, we study the optostructural properties of ultrathin non-van der Waals InGaS3 sheets produced by standard mechanical cleavage. Our ab initio calculation results suggest an emergence of authentically delicate out-of-plane covalent bonds within its unit cell, and, as a consequence, an artificial generation of layered structure within the material. Those yield to singular layer isolation energies of around 50 meVA-2, which is comparable with the conventional van der Waals material's monolayer isolation energies of 20 - 60 meVA-2. In addition, we provide a comprehensive analysis of the structural, vibrational, and optical properties of the materials presenting that it is a wide bandgap (2.73 eV) semiconductor with a high-refractive index (higher than 2.5) and negligible losses in the visible and infrared spectral ranges. It makes it a perfect candidate for further establishment of visible-range all-dielectric nanophotonics.