Characterization of 2D Hybrid Systems: Graphene and Beyond*

High-quality junction between semiconductor and metallic contact with no energy barrier is crucial for high-performance device, which is hard to achieve for 2D MoS₂ because of its large bandgap. The heterostructure of single-layers MoS₂/graphene has been demonstrated. However, a critical challenge has emerged: to develop reliable methods to transfer this graphene from its growth substrate to the application substrate without damaging the fragile patchwork or leaving undesired residues on the graphene surface. To ascertain the MoS₂ and graphene layer number and their defects, Confocal Raman spectroscopy and photoluminescence measurements were conducted before and after transfer. To identify the thin film thickness atomic force microscopy (AFM) was performed. Scanning electron microscopy was used to investigate the surface morphologies of MoS₂ and Graphene. To confirm the low surface defect results, X-ray Photoelectron Spectroscopy (XPS) was also carried out. We speculate that the tunable Fermi level in graphene allows excellent work-function to be well-matched with MoS₂, resulting in low contact resistance.