Carbon Nanotube Infrared Sensors Promise Smaller, Cheaper Thermal Cameras

Scientists at Skoltech have created a novel method for detecting infrared radiation without requiring cryogenic cooling, a development that could lead to more compact and cost-effective contactless thermometers and various sensors for medical, industrial, and safety applications. The technology relies on measuring the change in electrical conductivity of single-walled carbon nanotubes when exposed to infrared light.

This new approach demonstrated a conductivity change thousands of times more significant than that observed in graphene, a material previously used in similar detectors. The findings, published in Opto-Electronic Advances, address a key challenge in thermal detectors: minimizing measurement errors caused by ambient heat, known as thermal noise.

Traditional thermal detectors can sense a broad spectrum of infrared radiation at room temperature, but suffer from noise. Photonic detectors, while sensitive, require cooling, increasing complexity and cost. The Skoltech team's innovation enhances thermal detectors by replacing graphene with single-walled carbon nanotubes. When paired with lithium niobate, which generates an electric field upon heating, the nanotubes exhibit a resistance change 10,000 to 100,000 times greater than graphene.

This amplified response is attributed to the semiconducting nature of the nanotubes, which possess a bandgap allowing their conductivity to be precisely controlled by an electric field, unlike graphene. This pyroelectric phototransistor design converts absorbed light heat into a control signal with remarkable sensitivity across a wide range of infrared and even terahertz radiation. The high quality and defect-free transfer of the synthesized nanotubes onto the substrate were crucial for achieving this performance boost.