Introduction

Abstract

Low-symmetry in-plane anisotropic two dimensional (2D) materials cover a wide range of materials including black phosphorus, group IV monochalcogenides (GeS, GeSe, SnS, SnSe, etc.), Xenes (silicene, germanene, stanene, etc.), 2D organics (pentacene, dioctylbenzothienobenzothiophene (C8-BTBT), etc.), and more. These anisotropic 2D materials offer unique and rich low-dimensional physics in comparison to isotropic 2D materials including graphene, TMDs, etc. The reduced dimensionality and dielectric screening in such 2D materials and strong light–matter interaction in them lead to a high binding energy quasi-1D particle system. Hence, in-plane anisotropic 2D materials can provide much fertile land for novel optical, electronic, optoelectronic, thermoelectric, piezoelectric and ferroelectric applications compared to in-plane isotropic 2D materials. This introductory chapter firstly overviews the various types of anisotropic 2D materials. Then, it emphasizes their various anisotropic natures such as optical (absorption, photoluminescence and Raman scattering), electronic, thermal and mechanical anisotropies. Finally, it summarizes the potential device applications depending upon such anisotropies.