Dramatic Reduction of Contact Resistance via Ultrathin LiF in Two-Dimensional MoS₂ Field Effect Transistors

Molybdenum disulfide (MoS₂) has been regarded as one of the most important n-type two-dimensional (2D) transition metal dichalcogenide semiconductors for nanoscale electron devices. Relatively high contact resistance (R_C) remains as an issue in the 2D-devices yet to be resolved. Reliable technique is very compelling to practically produce low R_C values in device electronics, although scientific approaches have been made to obtain a record-low R_C. To resolve this practical issue, we here use thermal-evaporated ultrathin LiF between channel and source/drain metal to fabricate 2D-like MoS₂ field effect transistors (FETs) with minimum R_C. Under 4-bar FET method, R_C less than ∼600 Ω·μm is achieved from the LiF/Au contact MoS₂ FET. Our normal 2-bar FET with LiF thus shows the same mobility as that of 4-bar FET that should have no R_C in principle. On the basis of these results, ultrathin LiF is also applied for transparent conducting oxide contact, successfully enabling transparent MoS₂ FETs.