A computational study of metal-contacts to beyond-graphene 2D semiconductor materials

Among various 2D materials, monolayer transition-metal dichalcogenides (TMDs) with intrinsic band gaps (1.1-2.2 eV) are considered as promising candidates for next generation electronics. For applicability of these novel materials as transistors, a comprehensive understanding of metal contacts to them is an absolute necessity, which is lacking at present. In this paper, we report a systematic study of metal-TMD contacts with different geometries (end-contacts and side-contacts) by ab-initio density functional theory (DFT) calculations. Particularly, contacts between Au, Pd, In or Ti, and monolayer MoS₂ or WSe₂ are studied, respectively, including optimized geometries, partial density of states (PDOS), electron densities and effective potentials. Among the side-contacts to MoS₂, Ti shows the potential to form the best contacts, while for WSe₂ side-contacts, Pd exhibits the most advantages. We also find that end-contacts can be highly advantageous compared to side-contacts due to strong overlap of electron orbitals, absence of Schottky barriers and small tunnel barriers. Our modeling and simulation framework and results provide guidelines for novel 2D semiconductor device design and fabrication.