Optical lithography technique has been applied to fabricate devices from atomically thin sheets, exfoliated mechanically from kish graphite, bulk MoS2 and WSe2. During the fabrication processes, the exfoliated graphene, few-layer MoS2 and WSe2 sheets have been patterned into specific shapes as required and metal contacts have been deposited on these two-dimensional sheets to make field effect devices with different structures. The key to the successful implementation of the technique is the appropriate alignment mark design, which can solve the problems of aligning photomasks to the random location, orientation and irregular shape exfoliated two-dimensional sheets on the substrates. Raman characterization performed on the patterned two-dimensional sheets after the fabrication processes shows that little defects have been introduced during fabrication. Field effect has been observed from I–V characteristics with the highly doped silicon substrate as the back gate. The extracted field effect hole and electron mobilities of graphene are ~ 1010 cm2 V- 1 s- 1 and ~ 3550 cm2 V- 1 s- 1 respectively; and the field effect carrier mobilities of MoS2 and WSe2 are ~ 0.06 cm2 V- 1 s- 1 and ~ 0.03 cm2 V- 1 s- 1, separately, which are comparable with experimental results of other reports. 
Optical lithography technique for the fabrication of devices from mechanically exfoliated two-dimensional materials