Strain-Induced 2H to 1T' Phase Transition in Suspended MoTe₂ Using Electric Double Layer Gating.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Molybdenum disulfide (MoTe2) exhibits distinct semiconducting (2H) and semimetallic (1T') phases.
• Phase transitions in MoTe2 can be induced by heat, doping, or strain, with potential for electronic applications.

Purpose of the Study:

• To demonstrate a gate-controlled, fully reversible phase transition from the 2H to 1T' phase in few-layer suspended MoTe2.
• To explore the use of strain as a stimulus for phase transition in 2D materials.

Main Methods:

• Fabrication of few-layer suspended MoTe2 field-effect transistors.
• Application of strain via electric double-layer gating with a solid polymer electrolyte.
• Simultaneous electrical transport measurements and Raman spectroscopy to confirm phase transition.

Main Results:

• Observation of the A1g vibration peak, characteristic of the 1T' phase, at gate voltages (VSG) ≥ 2.5 V.
• Detection of a redshift in the E2g phonon mode, indicating strain-induced phonon shifts (0.2-0.3% strain).
• Transition of the temperature coefficient of resistance from negative to positive at VSG ≥ 2 V, confirming semiconducting-to-metallic transition.

Conclusions:

• A novel method for gate-controlled, reversible strain application in suspended 2D materials is presented.
• This technique facilitates the exploration of fundamental material properties and the development of new electronic device functionalities.
• The demonstrated reversible phase transition in MoTe2 holds promise for low-power memory and logic applications.