Modification of thermal transport in few-layer MoS₂ by atomic-level defect engineering

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Molybdenum disulfide (MoS2) is a 2D material with promising electronic and optoelectronic properties.
• Its thermal transport properties, crucial for device applications, have been underexplored.
• Point defects can significantly alter material properties.

Purpose of the Study:

• To investigate the impact of point defects on phonon transport in few-layer MoS2.
• To compare the effects of molybdenum (Mo) vacancies versus sulfur (S) vacancies on thermal conductivity.
• To establish a method for engineering thermal properties in 2D materials.

Main Methods:

• Few-layer MoS2 flakes were irradiated with helium ions (He+) to introduce controlled point defects.
• Thermal conductivity was measured using experimental techniques.
• Raman spectroscopy was employed to characterize defect concentration and crystalline structure.

Main Results:

• Molybdenum vacancies were found to significantly impede phonon transport, causing a greater reduction in thermal conductivity than sulfur vacancies.
• Raman spectroscopy revealed a red-shift in the E2g1 peak with increasing defect concentration, indicating damage to the in-plane crystalline network.
• A direct correlation was observed between increasing defect concentration and decreasing thermal conductivity.

Conclusions:

• Selective element removal, specifically creating Mo-vacancies, is an effective strategy for atomic-level engineering of phonon transport in MoS2.
• This approach offers potential for designing advanced thermal management devices utilizing 2D layered materials.
• Understanding defect-phonon interactions is key to tailoring thermal properties in nanomaterials.