Molybdenum Contacts to MoS<inf>2</inf> Field-Effect Transistors: Schottky Barrier Extraction, Electrical Transport, and Low-Frequency Noise

MoS2 has great interest for nanoscale electronic devices, including transistors and sensors. Defect-free structure, clean interface with the gate dielectric, and metals with suitable metal–semiconductor junctions are key for reliable devices. Molybdenum is shown as an excellent electrode for MoS2 field-effect transistors (FETs), but the correlation among device current, field-effect mobility, and the low-frequency noise (LFN) with number of atomic layers is not studied. Furthermore, the impact of Mo/MoS2 Schottky barrier on electronic injection and scattering in the device needs to be understood. Herein, by studying the FETs with channels of different numbers of atomic-layer thicknesses, it is shown that a molybdenum metal contact to MoS2 provides reliable current injection with low Schottky barrier height, low contact resistance, low electron–phonon scattering, and negligible impurity scattering. The mobility and LFN are optimal at a channel thickness of ≈12 atomic layers, which is consistent with the “mobility maximum window” in MoS2 transistors with prior studies using other contact metals.