Near-Field Radiative Nanothermal Imaging of Nonuniform Joule Heating in Narrow Metal Wires

Area of Science:

• Nanotechnology
• Thermodynamics
• Materials Science

Background:

• Accurate nanoscale temperature measurement is crucial for science and technology.
• Contact thermometers face limitations due to thermal contact interference.
• Infrared thermometers lack sufficient spatial resolution due to diffraction limits.

Purpose of the Study:

• To develop a noncontact method for mapping nanoscale temperature distributions.
• To overcome the spatial resolution limitations of conventional thermometers.
• To visualize and understand nanoscale thermal phenomena in operating devices.

Main Methods:

• Utilized a home-built sensitive infrared microscope combined with a noncontact scattering probe.
• Detected fluctuating electromagnetic evanescent fields on heated material surfaces.
• Developed a near-field infrared radiation thermometer with subwavelength spatial resolution (<100 nm).

Main Results:

• Successfully mapped nanoscale Joule heating on current-carrying metal wires.
• Identified localized "hot-spots" at sharp corners of bended wires.
• Simulation confirmed that current crowding causes nonuniform energy dissipation and localized heating.

Conclusions:

• The developed near-field infrared thermometer provides noninvasive nanoscale temperature mapping.
• Achieved spatial resolution far below the detection wavelength (λ/140).
• Demonstrated a temperature resolution of ~2 K at room temperature for operating nanoscale devices.