Band engineering for novel two-dimensional atomic layers

The discovery of graphene has sparked much interest in science and lead to the development of an ample variety of novel two-dimensional (2D) materials. With increasing research interest in the field of 2D materials in recent years, the researchers have shifted their focus from the synthesis to the modification of 2D materials, emphasizing their electronic structures. In this review, the possibilities of altering the band structures are discussed via three different approches: (1) alloying 2D materials, so called ternary 2D materials, such as hexagonal carbonized boron nitrides (h-BCN) and transition metal dichalcogenides (TMDs) ternary materials; (2) stacking 2D materials vertically, which results in 2D heterostructures named van der Waals (vdW) solids (using hexagonal boron nitrides (h-BN)/graphene and TMDs stacking as examples), and growing lateral TMDs heterostructrues; (3) controlling the thickness of 2D materials, that is, the number of layers. The electronic properties of some 2D materials are very sensitive to the thickness, such as in TMDs and black phosphorus (BP). The variations of band structures and the resulting physical properties are systematically discussed. Band engineering of novel two-dimensional materials is reviewed with a focus on three approaches, including the synthesis of ternary materials via alloying, the preparation of vertical and lateral heterostructures via stacking or epitaxially growing materials with similar atomic structure, and the control of thickness. The variations of band structures and the resulting physical properties are systematically discussed.