Extremely anisotropic van der Waals thermal conductors

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Integrated circuit (IC) miniaturization necessitates advanced thermal management.
• Materials with high thermal conductivity and anisotropic properties are crucial for controlling heat flow.
• Existing engineered thermal conductors exhibit limited anisotropy compared to natural materials.

Purpose of the Study:

• To develop novel artificial thermal conductors with extremely high anisotropy ratios.
• To investigate the role of interlayer rotations in van der Waals (vdW) thin films for thermal transport.
• To demonstrate the potential of these materials for thermal management in electronic devices.

Main Methods:

• Fabrication of large-area vdW thin films (MoS2, WS2) with random interlayer rotations.
• Measurement of in-plane and through-plane thermal conductivity using specialized techniques.
• Molecular dynamics (MD) simulations to elucidate thermal transport mechanisms.

Main Results:

• Achieved a record room-temperature thermal anisotropy ratio close to 900 in MoS2 films.
• Measured ultralow through-plane thermal conductivities (MoS2: 57±3 mW m⁻¹ K⁻¹, WS2: 41±3 mW m⁻¹ K⁻¹).
• Demonstrated high in-plane thermal conductivity comparable to single crystals.
• MD simulations revealed 1D glass-like thermal transport in the through-plane direction.

Conclusions:

• Engineered vdW films with random interlayer rotations offer unprecedented thermal anisotropy.
• Interlayer rotations effectively impede through-plane heat transport while preserving in-plane conductivity.
• These anisotropic materials show promise for preventing overheating in nanofabricated electrodes and devices.
• Interlayer rotation presents a new design paradigm for directed heat transport in solid-state systems.