Mobility Enhancement and Highly Efficient Gating of Monolayer MoS$_{2}$ Transistors with Polymer Electrolyte

We report electrical characterization of monolayer molybdenum disulfide (MoS$_{2})$ devices using a thin layer of polymer electrolyte consisting of poly(ethylene oxide) (PEO) and lithium perchlorate (LiClO$_{4})$ as both a contact-barrier reducer and channel mobility booster. We find that bare MoS$_{2}$ devices (without polymer electrolyte) fabricated on Si/SiO$_{2}$ have low channel mobility and large contact resistance, both of which severely limit the field-effect mobility of the devices. A thin layer of PEO/ LiClO$_{4}$ deposited on top of the devices not only substantially reduces the contact resistance but also boost the channel mobility, leading to dramatically enhancement of the field-effect mobility of the device. When the polymer electrolyte is used as a gate medium, the MoS$_{2}$ field-effect transistors exhibit excellent device characteristics such as a near ideal subthreshold swing and an on/off ratio of 10$^{6}$ as a result of the strong gate-channel coupling.