Single-Nanoparticle Plasmon-Driven Phase Engineering of Two-Dimensional MoTe₂.

Area of Science:

• Materials Science
• Nanotechnology
• Condensed Matter Physics

Background:

• All-optical control of material phases at the nanoscale is crucial for reconfigurable nanophotonic and sensing platforms.
• Few-layer transition metal dichalcogenides (TMDs) exhibit distinct properties based on their crystalline phase.

Purpose of the Study:

• To present a plasmon-driven strategy for all-optical writing and reading of localized phase transitions in few-layer Molybdenum Ditelluride (MoTe2).
• To demonstrate the use of individual gold nanoparticles (Au NPs) as dual-function nanoantennas for phase engineering and optical readout.
• To explore the application of this phase transition control in nanoscale thermal sensing and reconfigurable heterostructures.

Main Methods:

• Utilizing individual Au NPs as nanoantennas to concentrate laser excitation via localized surface plasmon resonances (LSPRs).
• Driving the 2H→1T' phase transition in few-layer MoTe2 using hot carriers and local heating generated by plasmonic excitation.
• Employing dark-field scattering spectroscopy for in situ optical readout of the phase transition, observing characteristic spectral shifts.
• Confirming the 1T' phase formation using Raman spectroscopy.
• Fabricating and characterizing vertical heterostructures (e.g., Au/MoTe2/MoS2) to study plasmon-induced band alignment reconfiguration.

Main Results:

• Achieved a plasmon-driven 2H→1T' phase transition in few-layer MoTe2 with a threshold power reduced by nearly an order of magnitude.
• Demonstrated in situ optical readout of the phase transition via characteristic redshift-then-blueshift behavior in dark-field scattering spectra.
• Confirmed the temperature-dependent scattering response of the Au NP/1T'-MoTe2 system, enabling nanoscale optical thermal sensing.
• Showcased reconfiguration of band alignment in an Au/MoTe2/MoS2 heterostructure, switching from a photoluminescence-quenched OFF state to a trion-dominated ON state via plasmon-induced phase conversion.

Conclusions:

• Established a general route for all-optical, nanoscale phase engineering of 2D materials.
• Highlighted the potential for active thermal and excitonic control in nanophotonic devices through controlled phase transitions.
• Demonstrated the dual functionality of Au NPs as nanoantennas for both inducing and reading out nanoscale phase changes.