Surface-engineered Mo2C: an ideal electrode for 2D semiconductor-based complementary circuit with Schottky-barrier-free contacts

Abstract

The achievement of complementary metal-oxide-semiconductor (CMOS) logic functions and the elimination of Schottky barrier (SB) in two-dimensional (2D) field-effect transistors (FETs) remain critical challenges. Here, by first-principles calculation, a novel straightforward strategy has been provided to achieve CMOS logic functions and SB-free contacts simultaneously in 2D FETs through modifying the surface electrical structure of Mo2C electrode with different groups. Both Mo2C with surfaces fully saturated by O (Mo2CO2) and OH (Mo2C(OH)2) groups are energetically and dynamically stable. Importantly, the interfaces between 2D layered semiconductors (2DLSCs) and Mo2C with fully saturated surfaces show van der Waals contacts, effectively suppressing the Fermi level pinning, making the SB can be modulated by adjusting the work function of electrode. Therefore, Mo2C(OH)2 likely forms n-type contacts with 2DLSCs because of its ultralow work function, whereas Mo2CO2 prefers to form p-type contacts with 2DLSCs because of its ultrahigh work function. Remarkably, all Mo2C(OH)2/2DLSCs and Mo2CO2/2DLSCs systems can form Ohmic contacts. Through this novel strategy, the zero SB height in 2D FETs and the controllable contact polarity (n-type or p-type) in CMOS logic functions can be achieved readily. This work illustrates a novel and powerful method for developing high-performance 2D semiconductor-based complementary circuit.