Percolative phase transition in few-layered MoSe₂ field-effect transistors using Co and Cr contacts

Area of Science:

• Condensed matter physics
• Materials science
• Nanotechnology

Background:

• The metal-to-insulator phase transition (MIT) in two-dimensional (2D) materials is crucial for next-generation electronics.
• Understanding electron transport mechanisms in 2D semiconductors is an ongoing challenge.
• Gating electric fields enable tunable electronic properties in 2D materials.

Purpose of the Study:

• To investigate the tunable percolative phase transition in few-layered MoSe2 field-effect transistors (FETs).
• To compare the effect of different metallic contact materials (Cr and Co) on the MIT.
• To understand the MIT mechanism through temperature-dependent electronic transport measurements.

Main Methods:

• Fabrication of MoSe2 FETs with Cr and Co metallic contacts.
• Temperature-dependent electronic transport measurements (50 K to room temperature).
• Tuning carrier density via gate voltage and analyzing conductivity data.

Main Results:

• Both Cr and Co contacts exhibited n-type behavior with significant mobility enhancements at low temperatures.
• Devices with Co contacts showed higher room-temperature and low-temperature mobilities compared to Cr contacts.
• Conductivity transition from insulating-to-metallic behavior was observed, with Co contacts aligning well with 2D percolation theory.

Conclusions:

• The choice of metallic contact material significantly influences the MIT in few-layered MoSe2 FETs.
• Cobalt contacts facilitate electron transport behavior that closely follows 2D percolation theory.
• Cr contacts showed deviations from 2D percolation theory at low temperatures, indicating different transport mechanisms.