Large-area thermoelectric high-aspect-ratio nanostructures by atomic layer deposition

Area of Science:

• Materials Science
• Nanotechnology
• Solid State Physics

Background:

• Thermoelectric generators (TEGs) offer a promising route for waste heat recovery.
• Improving the efficiency of TEGs requires optimizing both electrical and thermal transport properties.
• Nanostructuring materials presents a viable strategy to decouple these properties.

Purpose of the Study:

• To investigate the thermoelectric properties of large-area, high-aspect-ratio zinc oxide (ZnO) nanostructures.
• To evaluate the potential of these nanostructures for enhancing the performance of thin-film thermoelectric generators.
• To understand the influence of nanostructure geometry on electrical and thermal transport.

Main Methods:

• Fabrication of ZnO nanostructures via atomic layer deposition (ALD) on track-etched polycarbonate substrates.
• Characterization of the resulting ZnO tubules' morphology and crystal structure.
• Measurement of in-plane and out-of-plane electrical and thermal properties.

Main Results:

• Achieved very low out-of-plane thermal conductivity (down to 0.15 W m⁻¹ K⁻¹).
• Observed in-plane sheet resistance to be half that of ZnO films on glass substrates.
• Demonstrated material-independent doubling of output power for planar TEGs.
• Controlled ZnO nanotube wall thickness up to 100 nm with preferred (002) crystal orientation.

Conclusions:

• Large-area, high-aspect-ratio ZnO nanostructures exhibit excellent thermoelectric potential.
• The unique nanostructure design significantly enhances thermoelectric performance by reducing thermal conductivity.
• These findings pave the way for more efficient waste heat recovery applications using thin-film TEGs.