Nanotip Contacts for Electric Transport and Field Emission Characterization of Ultrathin MoS Flakes.

We report a facile approach based on piezoelectric-driven nanotips inside a scanning electron microscope to contact and electrically characterize ultrathin MoS2 (molybdenum disulfide) flakes on a SiO2/Si (silicon dioxide/silicon) substrate. We apply such a method to analyze the electric transport and field emission properties of chemical vapor deposition-synthesized monolayer MoS, used as the channel of back-gate field effect transistors. We study the effects of the gate-voltage range and sweeping time on the channel current and on its hysteretic behavior. We observe that the conduction of the MoS channel is affected by trap states. Moreover, we report a gate-controlled field emission current from the edge part of the MoS flake, evidencing a field enhancement factor of approximately 200 and a turn-on field of approximately   40   V / μ m at a cathode-anode separation distance of 900   nm .