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

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.