Imaging Heat Transport in Suspended Diamond Nanostructures with Integrated Spin Defect Thermometers

Area of Science:

• Materials Science
• Nanotechnology
• Condensed Matter Physics

Background:

• Monocrystalline diamond exhibits exceptionally high thermal conductivity (>2000 W/m/K).
• Diamond nanostructures are crucial for advanced photonics, electronics, and quantum technologies, necessitating effective heat dissipation.
• Predicting heat flow at the nanoscale is challenging due to dominant normal phonon-phonon scattering.

Purpose of the Study:

• To image temperature inhomogeneities in single-crystal diamond microstructures.
• To investigate nanoscale heat flow and thermal transport properties.
• To understand the mechanisms behind reduced thermal conductivity in diamond nanostructures.

Main Methods:

• Utilized dilute nitrogen-vacancy color centers as in situ spin defect thermometers.
• Analyzed diamond cantilevers with cross-sections ranging from 0.2 to 2.6 μm².
• Employed first-principles simulations based on the linearized phonon Boltzmann transport equation and viscous heat equations.

Main Results:

• Observed a significant reduction in thermal conductivity as cantilever width decreased.
• Quantitatively predicted thermal transport properties, explaining the observed nondiffusive behavior.
• Demonstrated the interplay between intrinsic and extrinsic phonon scattering mechanisms.

Conclusions:

• The study reveals unconventional, nondiffusive heat transport in diamond nanostructures.
• The developed temperature-imaging method is applicable to nanostructures of various geometries.
• This work provides insights into thermal management challenges in nanoscale devices.