Phase transition in WSe_2-Te monolayers driven by charge injection and pressure: a first-principles study.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Alloying transition metal dichalcogenides (TMDs) offers tunable properties for electronic applications.
• Understanding the structural stability and phase transition mechanisms in alloy TMDs, especially under external fields, remains a challenge.

Purpose of the Study:

• To investigate the structural phase transition mechanism in WSe2-xTex monolayers.
• To explore the influence of tellurium enrichment and external fields (charge injection, tensile strain) on phase stability and transition barriers.

Main Methods:

• First-principles calculations were employed to study WSe2-xTex monolayers.
• Crystal Orbital Hamiltonian Population (COHP) analysis was used to probe bonding states and structural stability.
• The effect of varying tellurium content, electron concentration, and tensile strain was systematically investigated.

Main Results:

• Enrichment of tellurium in WSe2-xTex monolayers drives a coherent structural transition from the H phase to the T' phase.
• Increased tellurium concentration destabilizes the H phase by shifting bonding states near the Fermi level, lowering the transition energy barrier.
• Charge injection can trigger the H-to-T' phase transition, with the critical electron concentration decreasing as tellurium content increases.
• Tensile strain effectively reduces the energy barrier for the H-to-T' phase transition.

Conclusions:

• Alloying WSe2 with Te provides a pathway to control structural stability and semiconductor-semimetal phase transitions.
• Charge injection and tensile strain offer external stimuli to tune the phase transition, paving the way for novel phase-change electronic devices.
• This study offers critical insights for the design of phase-sensitive devices utilizing alloyed TMDs.