Flexible 2D FETs using hBN dielectrics

Two-dimensional (2D) materials such as graphene and molybdenum disulfide (MoS₂) are promising for flexible electronics because of their combination of unique electrical properties and mechanical robustness. However, conventional oxides are not well matched as complementary dielectrics for 2D channel materials. Trapped charges typically present in oxide-based dielectrics, result in increased scattering of charge carriers in device channels. We have pioneered the use of a 2D dielectric, hexagonal boron nitride (hBN), as a better alternative: it can by highly crystalline and as an insulating analogue of graphene, it lacks dangling bonds at its surface, making it an ideal complement to 2D conducting materials. We have recently demonstrated a new technique to assemble layered heterostructures by `van der Waals transfer´. This process eliminates exposure of the active device layer to polymers and provides atomically clean interfaces even for devices fabricated in ambient conditions. For electrical contact to encapsulated graphene layers, we have demonstrated a second technique, in which the entire stack is etched to expose a one-dimensional edge of the channel. Metal electrodes applied to this edge create a robust contact with resistance approaching 100 -μm.