Dimensionality matters: Electronic transport in 2D layered materials

Abstract

It seems to be unavoidable that the first question that anyone asks when a new material is introduced fo electronic device applications is: “What mobility does this material have?” In fact, this question can be rather misleading, like in the context of graphene, where the absence of a bandgap immediately prohibits its use for transistor applications despite its outstanding mobility values. In addition, quoting mobilities without specifying the actual body thickness of the material under investigation can also easily result in a misinterpretation. It has long been known for example that the mobility of silicon rapidly degrades once its thickness reaches about 10nm For sub-1nm body thicknesses any three-dimensional 3D crystal becomes simply non-conducting. With this in mind, recently reported transport data on two-dimensional (2D) semiconducting materials as transition meta dichalcogenides (TMDs) and black phosphorus (BP) with body thicknesses tbody in the nm-range become quit impressive, even if their mobilities cannot rival graphene.