ABSTRACT
The recent emergence of a wide variety of two-dimensional (2D) materials has created new opportunities for device concepts and applications. In particular, the availability of semiconducting transition metal dichalcogenides, in addition to semimetallic graphene and insulating boron nitride, has enabled the fabrication of "all 2D" van der Waals heterostructure devices. Furthermore, the concept of van der Waals heterostructures has the potential to be significantly broadened beyond layered solids. For example, molecular and polymeric organic solids, whose surface atoms possess saturated bonds, are also known to interact via van der Waals forces and thus offer an alternative for scalable integration with 2D materials. Here, we demonstrate the integration of an organic small molecule p-type semiconductor, pentacene, with a 2D n-type semiconductor, MoS2. The resulting p-n heterojunction is gate-tunable and shows asymmetric control over the antiambipolar transfer characteristic. In addition, the pentacene/MoS2 heterojunction exhibits a photovoltaic effect attributable to type II band alignment, which suggests that MoS2 can function as an acceptor in hybrid solar cells.
ABSTRACT
The full potential of graphene in integrated circuits can only be realized with a reliable ultrathin high-κ top-gate dielectric. Here, we report the first statistical analysis of the breakdown characteristics of dielectrics on graphene, which allows the simultaneous optimization of gate capacitance and the key parameters that describe large-area uniformity and dielectric strength. In particular, vertically heterogeneous and laterally homogeneous Al2O3 and HfO2 stacks grown via atomic-layer deposition and seeded by a molecularly thin perylene-3,4,9,10-tetracarboxylic dianhydride organic monolayer exhibit high uniformities (Weibull shape parameter ß > 25) and large breakdown strengths (Weibull scale parameter, E(BD) > 7 MV/cm) that are comparable to control dielectrics grown on Si substrates.
