Probing van der Waals interactions at two-dimensional heterointerfaces.

Abstract

Two-dimensional (2D) heterostructures assembled via van der Waals (vdW) interactions have sparked immense interest in fields from physics1,2 to electronics3,4. Understanding the vdW interaction at these heterointerfaces is critical for the sophisticated construction and manipulation of these 2D heterostructures. However, previous experimental research has mainly focused on the interlayer interactions in homogeneous graphite crystals5,6 and the interactions between graphene and substrates7. Theoretically, although a variety of vdW methods have been incorporated in density functional theory to probe the interactions of homogeneous vdW crystals, the reliability of these vdW methods in 2D heterostructures remains to be verified. Here, we show, by contact-splitting transfer of graphite from hexagonal boron nitride (BN) to molybdenum disulfide (MoS2), that graphite experiences a stronger vdW interaction with MoS2 than with boron nitride. Quantitative measurements using a graphite-wrapped atomic force microscope tip show that the critical adhesion pressures between BN and graphite and MoS2 and graphite are respectively 0.953 and 1.028 times that between graphite and graphite. The results are consistent with the prediction based on Lifshitz theory, implying an important role of material dielectric function in the vdW interactions at heterointerfaces. These findings offer us more freedom in the construction of 2D heterostructures, and a technique to disassemble 2D heterostructures is demonstrated.