Reports

The advent of graphene (1) and the subsequent discovery of its multitude of superior properties (2–5) has led to the identification of many other two-dimensional (2D) crystals (6) through both chemical modification of graphene and exfoliation of other lay-ered compounds. This new area of research and progress in pre-cise transfer of the crystals while maintaining their quality (7, 8) has resulted in the emergence of a new class of materials: hetero-structures based on 2D atomic crystals (5, 8, 9). More specifical-ly, there is the possibility to create hybrid materials by stacking combinations of 2D crystals with differing properties. These structures are interesting from both fundamental and application points of view. It has, for instance, been shown that layering sheets of graphene and hexagonal boron nitride (hBN), molyb-denum disulfide (MoS2), or tungsten disulfide (WS2) allows op-eration of tunneling transistors (9, 10) and permitted th