High-performance large-area WS2-based transistors by a novel tin-oxide assisted liquid-phase exfoliation: doping adjustment by plasma treatment

Abstract We report a novel strategy to stitch small WS 2 flakes to form larger features in liquid-phase exfoliation. Owing to the initial granular size of the bulk WS 2, which, is around 2 µ m, the use of conventional liquid-based exfoliation techniques leads to small area nanoflakes with sizes around 1 μ m. However, by joining smaller flakes through tin-oxide quantum dot (SnO 2 QD) decoration during probe sonication, sheets up to 20 μ m are achieved. The neighboring flakes could stitch together to form larger features through the Sn–S and Sn–O bonds at their lateral sides of their flakes and to realize mosaic arrangement of arbitrary shaped larger sheets. While the original WS 2 flakes show n-type behavior, an interesting conversion into a p-channel behavior is observed upon addition of SnO 2 QDs followed by additional SF 6 plasma treatment process. Additionally, we have investigated the use of SF 6 plasma treatment to enhance the carrier mobility and on-off ratio of the field effect transistors, yielding an effective field-effect-mobility of 80 cm 2 V −1 s −1 and relatively high on/off current ratio of 10 5 , indicating its superior electronic properties.