Adhesion Between MXenes and Other 2D Materials.

MXenes, a large family of two-dimensional (2D) early transition metal carbides and nitrides, have excellent electrical and electrochemical properties, which can also be explored in assemblies with other 2D materials, like graphene and transition metal dichalcogenides (TMDs), creating heterostructures with unique properties. Understanding the interaction mechanism between 2D materials is critical for the design and manipulation of these 2D heterostructures. Our previous work investigated the interaction between SiO2 and two MXenes (Ti3C2Tx and Ti2CTx). However, no experimental research has been done on MXene interlayer interactions and interactions in MXene heterostructures. Here, we used atomic force microscopy (AFM) with SiO2 tip and Ti3C2Tx and Ti2CTx MXene-coated tips, respectively, to measure the adhesion energies of graphene, MoSe2, Ti3C2Tx, and Ti2CTx MXene with other 2D materials. The measured adhesion energies show that only the interfaces involving graphene demonstrate dependence on the number of material monolayers in a stack. Comparing 40 interacting pairs of 2D materials, the lowest adhesion energy (∼0.27 J/m2) was found for the interfaces involving MoSe2 and the highest adhesion energy was observed for the interfaces involving Ti3C2Tx (∼1.23 J/m2). The obtained set of experimental data for 2D interfaces involving MXenes provides a basis for a future in-depth understanding of adhesive mechanisms at interfaces between 2D materials, which is an important topic for the design of 2D heterostructures with controlled interfacial strength and properties.