When 2D materials meet metals

Abstract

Abstract This review delves into the intricacies of the interfaces formed between two-dimensional (2D) materials and metals, exploring a realm rich with fundamental insights and promising applications. Historically, our understanding of 2D materials emanated from studies employing dielectric substrates or suspended samples. However, integrating metals in the exfoliation and growth processes of 2D materials has opened up new avenues, unveiling various shades of interactions ranging from dispersive forces to covalent bonding. The resulting modifications in 2D materials, particularly transition metal dichalcogenides (TMDCs), offer more than a theoretical intrigue. They bear substantial implications for (opto)electronics, altering Schottky barrier heights and contact resistances in devices. We explore metal-mediated methods for TMDC exfoliation, elucidating the mechanisms and their impact on TMDC-metal interactions. Delving deeper, we scrutinize the fundamentals of these interactions, focusing primarily on MoS2 and Au. Despite the recent surge of interest and extensive studies, critical gaps remain in our understanding of these intricate interfaces. We discuss controversies, such as the changes in Raman or photoemission signatures of MoS2 on Au, and propose potential explanations. The interplay between charge redistribution, substrate-induced bond length variations, and interface charge transfer processes are examined. Finally, we address the intriguing prospect of TMDC phase transitions induced by strongly interacting substrates and their implications for contact design.