2D 2D covalent heterostructures: High-throughput on-device connection of MoS2 and graphene

Abstract

Resumen del póster presentado a la XXXVIII Reunión Bienal de la Real Sociedad Española de Química, celebrada en el Palacio de Congresos de Granada, del 27 de junio al 30 de junio de 2022.The most widespread method for the synthesis of 2D-2D heterostructures is the direct growth of one material on top of the other. Alternatively, one can manually stack flakes of different materials. Both methods are limited to one crystal/device at a time and involve interfacing the 2D materials through van der Waals forces, to the point that all these materials are known as van der Waals heterostructures. Synthetic chemistry is the paradigm of atomic-scale control, yet its toolbox remains unexplored for the construction of 2D-2D heterostructures. Here, we describe how to covalently connect 2H-MoS2 flakes to several single-layer graphene field-effect transistors simultaneously, and show that the final electronic properties of the MoS2-graphene heterostructure are dominated by the molecular interface. We use a bifunctional molecule with two chemically orthogonal anchor points, selective for sulfides and carbon-based materials: On one hand, we exploit the chemistry of maleimide described by our group to functionalize sulfide-based materials under mild conditions. On the other hand, we use a diazonium salt, which is the most common method for the covalent modification graphene. The solvents play a key role to activate a specific part of the molecule for the covalent anchoring. In order to measure the electrical properties of the heterostructure, we have fabricated a number of f-MoS2@graphene field effect transistors (FET) on Si/SiO2 substrates. The electronic properties of the functionalized devices are dominated by the chemical interface, resulting in p-doped devices in which the charge mobility is conserved after reaction, and the degree of doping can be controlled by increasing the degree of functionalization. The results described here show the power of the chemical approach to build functional 2D-2D heterostructures beyond van der Waals. Figure 1: Experimental procedure for the production of MoS2@Graphene covalent heterostructures.Peer reviewe