(Invited) Covalent Functionalization of Graphene and MoS2 : Towards Nanometer Scale Chemical Patterning

Abstract

Atomically thin sheets of materials (2D materials) came to prominence in the early 2000s with the successful isolation of graphene. Since then, the interest in graphene has steadily increased thanks to its exceptional electronic, optical, mechanical and thermal properties. It also led to the isolation of other 2D materials such as black phosphorous, silicene, germanene and transition metal dichalcogenides (TMDs) such as MoS2. Due to their exceptional properties, these materials offer virtually endless opportunities for fundamental research as well as cutting edge applications.Most of these 2D materials can be stabilized by the covalent attachment of organic molecules. For instance, the chemisorption of organic units can promote the stabilization of dispersions of 2D materials in organic solvents improving their solution processability. Moreover, such chemisorption of organic molecules allows manipulation of their physicochemical properties by addition of desired functional groups in a tailor made fashion. However, controlling the spatial distribution of the covalently bound units remains a major challenge due to the highly reactive nature of the reagents used for the covalent modification process.In this talk, I will discuss the covalent modification of graphene, graphite and MoS2 using diazonium chemistry. The chemically activated decomposition of diazonium salts using mild conditions will be discussed in detail. The characterization of the modified materials using atomic force microscopy (AFM), scanning tunnelling microscopy (STM), and Raman spectroscopy will be presented. The micrometre-scale multicomponent patterning of surface-supported graphene achieved through a combination of e-beam lithography and diazonium chemistry will also be discussed. The impact of this functionalization on the surface potential will be evaluated through scanning probe microscopies. Lastly, I will also show how the chemical patterning can be extended to the lower end of the nanoscale by using physisorbed self-assembled monolayers of alkanes as sacrificial templates.