Dual-Functional LiF for Concurrent Contact and Channel Modulation in Monolayer MoS ₂ Transistors

Transistors are the key components in many functional electronics. The performance of n-type field-effect transistors (FETs) based on MoS 2 is limited not only by metal–semiconductor contact performance (e.g. high contact resistance and Schottky barrier height) but also restricted by the interfacial disorders and scattering effects at active channels. In this work, we report a systematic study of lithium fluoride (LiF) used concurrently as a tunneling layer at the metal–MoS 2 interface and a capping layer on the active channel in monolayer MoS 2 FETs. An ultrathin LiF layer (~2 nm) is thermally deposited before the metal deposition, which behaves as a tunneling layer. In addition, another LiF capping layer (~10 nm) is deposited on the active channel to mitigate interfacial disorder and screen remote scattering effects, thereby improving intrinsic channel transport. According to the electrical transport characterization, the device shows significant improvement in terms of on-state current (~83% increase), two-terminal field-effect mobilities (~40% increase) and on-off ratio (~2-fold increase) by adopting this proposed strategy. These results elucidate the role of ionic wide-bandgap insulating layers in the synergistic modulation of contacts and channels in two-dimensional semiconductors and provide a simple, generalizable pathway to high-performance, energy-efficient two-dimensional electronics.