Ambipolar transport in CVD grown MoSe₂ monolayer using an ionic liquid gel gate dielectric

Ambipolar charge transport was observed in CVD grown crystalline MoSe₂ monolayers using an ionic liquid gel gate dielectric in a field effect transistor configuration. Gold electrode contacts with the device resulted in Schottky barriers that were higher for electron transport. Applying a gate voltage lowers this barrier allowing electrons and holes to flow through the same channel at room temperature. The threshold voltage for electron transport was lower than that for holes indicating strong electron doping or Fermi level pinning to the conduction band. The high specific capacitance of the ion gel permitted device operation at low applied voltages. Preliminary calculations for the electron (hole) mobility was found to be 0.2 (0.1) cm²/V-s and the on/off ratio was ~10⁶ for holes and electrons. The device was successfully tested in a resistor loaded inverter circuit and showed a gain of ~3. The ambipolar feature of MoSe₂ makes it an excellent candidate for use in low power consumption flexible complimentary logic circuits.