Ohmic Contact in 2D Semiconductors via the Formation of a Benzyl Viologen Interlayer

The fabrication of a polymeric Ohmic contact interlayer between a metal and a 2D material using solution-processed benzyl viologen (BV) is reported here. Predoping of the polymer alters the contact surface to obtain electron-doped materials with ultrahigh work functions that significantly enhance the current density across the contact and reduce the contact resistance and Schottky barrier height. The fabrication of solution-processed polymeric contacts for the preparation of high mobility MoS2, WSe2, MoTe2, and BP (black phosphorous) FETs with significantly lowered contact resistance is demonstrated. Ohmic contacts are achieved and produce 3-, 700-, 3000-, and 17-fold increases in electron mobilities, respectively, when the bottom gate voltage is 10 V compared to those respective materials alone. Ambipolar and p-type 2D material based FETs could, therefore, be transformed into n-type FETs. Most importantly, the devices exhibit excellent stability in both ambient and vacuum.