Innovative Selected Area Doping and Stable Contact for 2D WSe2 Electronics Using Patterned Nafion

Abstract Selective area doping and contact resistance (RC) lowering in two dimensional (2D) semiconductors have been persistent issues for 2D semiconductor based electronics. Such doping in 2D seems almost impossible unlike in 3D semiconductors, which use ion implantation. Furthermore, maintaining a low and stable RC in 2D seems very difficult. Here, we report a strategy for area selective doping of 2D materials: electron-beam patterning of sulfonated tetrafluoroethylene-based fluoropolymer-copolymer (Nafion) underlayer with a large work function. Patterned-underlayer selectively increases the hole density of p-type WSe2, whose sheet resistance becomes compatible for integrated circuit. Top-gated WSe2 field-effect transistor channel, as modulated with Nafion area, demonstrates 7 times higher mobility than without Nafion. As patterned for contact area, Nafion directly lowers RC to ~ 6 kΩ-µm, which is maintained for 2 months in air ambient and survives N2 anneal of 200 o C. Our Nafion approach for selective 2D doping and stable RC seems advanced and practically useful.