Improved contacts to two-dimensional materials for extracting emergent properties

It is critical to control the properties of electrical contacts to two-dimensional (2D) material systems such as twisted bilayer graphene or superconducting 2D systems in order to probe and properly extract their emergent quantum properties. We present here effective routes for contact engineering. It has been demonstrated that TMD monolayers can be effectively doped by using molecular reductants and oxidants introduced onto the surface from solution. [1] In this study, we investigated the effects of molecular doping and contact engineering on the 2D/metal interfaces and charge transport properties of MoS₂ devices. We show that MoS₂ p-type FETs can only be achieved through combining molecular doping and high-work function metals (e.g. Pd) [2]. We have demonstrated an exposed material forming gas cleaning anneal that effectively decreases deleterious organic contamination arising during fabrication as evidenced by uniform and improved field-effect transistor (FET) performance metrics [3] such as field-effect mobility and threshold voltage.
[1] S. Zhang, et al., Adv. Mater. 30, 1802991 (2018); [2] S. Zhang et al., Appl. Phys. Lett. 115, 073106 (2019); [3] N. Guros, et al., ACS Appl. Mater. Interfaces. 11, 16683 (2019).