Century-old limit on turning heat into electricity surpassed, enabling ultrasensitive temperature sensing

Key Highlights:

• Scientists have discovered a crystalline semiconductor, Scandium Nitride (ScN), that converts a temperature difference into an electrical voltage nearly a thousand times larger than previously observed limits in solids.
• This breakthrough surpasses a century-old assumption about the ceiling of the Seebeck effect in solid materials.
• The research was conducted by scientists from Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), University of Sydney, and Indian Institute of Science (IISc).
• The enhanced thermoelectric effect was achieved in heavily doped, highly compensated (HDHC) ScN thin films.
• This discovery paves the way for a new generation of ultrasensitive temperature sensors, heat detectors, and quantum sensing devices.

Detailed Insights:

• The finding overturns a decades-old assumption that the Seebeck effect in crystalline solids was limited to a few millivolts per Kelvin.
• Previously, such large thermoelectric voltages were typically seen only in liquid electrolytes and ionic gels, not in solid, single-crystalline materials.
• Researchers deliberately doped ScN with magnesium to create an HDHC semiconductor, which exhibited this unprecedented effect.
• The measured Seebeck coefficient exceeded –124.6 millivolts per Kelvin near room temperature, significantly higher than typical semiconductors.
• The thermoelectric effect was observed to grow even stronger as the HDHC ScN films were made thinner.
• A preliminary prototype photon sensor using HDHC ScN film showed potential for single-photon-level detection.
• Potential applications include low-noise thermal imaging, bolometric devices, Internet-of-Things (IoT) sensors, and cryogenic thermoelectric single-photon detectors for quantum technologies.

Scientific/Technical Concepts Involved:

• Seebeck Effect: The phenomenon where a temperature difference across a material generates an electrical voltage.
• Seebeck Coefficient: A measure of the magnitude of the thermoelectric voltage produced per unit of temperature difference.
• Thermoelectric Voltage: The electrical potential difference generated in a material due to a temperature gradient.
• Heavily Doped, Highly Compensated (HDHC) Semiconductor: A semiconductor material containing nearly equal numbers of randomly distributed positive and negative dopant atoms.