Approaching Ohmic Contacts for Ideal Monolayer MoS 2 Transistors Through Sulfur-Vacancy Engineering.

Field-effect transistors (FETs) made of monolayer 2D semiconductors (e.g., MoS 2 ) are among the basis of the future modern wafer chip industry. However, unusually high contact resistances at the metal-semiconductor interfaces have seriously limited the improvement of monolayer 2D semiconductor FETs so far. Here, a high-scale processable strategy is reported to achieve ohmic contact between the metal and monolayer MoS 2 with a large number of sulfur vacancies (SVs) by using simple sulfur-vacancy engineering. Due to the successful doping of the contact regions by introducing SVs, the contact resistance of monolayer MoS 2 FET is as low as 1.7 kΩ·µm. This low contact resistance enables high-performance MoS 2 FETs with ultrahigh carrier mobility of 153 cm 2 V -1 s -1 , a large on/off ratio of 4 × 10 9 , and high saturation current of 342 µA µm -1 . With the comprehensive investigation of different SV concentrations by adjusting the plasma duration, it is also demonstrated that the SV-increased electron doping, with its resulting reduced Schottky barrier, is the dominant factor driving enhanced electrical performance. The work provides a simple method to promote the development of industrialized atomically thin integrated circuits.