Solvent-assisted exfoliation for high-quality molybdenum disulfide nanoflakes and relevant field-effect transistors

Mechanical exfoliation is a facile way for the preparation of two-dimensional (2D) nanoflakes. However, the quality of obtained flakes still needs to be further improved, e.g., the exfoliated size and production yield, which plays a crucial role in practical applications. Here, solvent-assisted method is proposed by introducing chemical solvents in the exfoliations. The impacts of wrinkles and defects existed in the outmost layer of bulk MoS 2 crystal are overcome due to the capillary and diffusion forces driven by solvent molecules underlying flakes. Hence, the size and yield of nanoflakes are promoted manifestly. The MoS 2 nanoflakes are obtained with the largest area of ~ 1.5 mm 2 that is three orders of magnitude bigger than conventional mechanical exfoliation. In addition, the characterizations verify the existence of monolayer which may exhibit intrinsic properties of the MoS 2 flakes. Subsequently, MoS 2 field-effect transistors are conveniently fabricated by one-step mechanical shadow-mask process. The field-effect mobility of ~ 26 cm 2 V −1 s −1 and on/off ratio of ~ 10 6 are achieved. All results indicate that the solvent-assisted exfoliations provide a universal path in the preparation of 2D nanoflakes, which is a fundamental support for the studies of 2D materials and devices. Graphical abstract