Lock-in thermography using diamond quantum sensors

Precise measurement of temperature distribution and thermal behavior in microscopic regions is critical in many research fields. We demonstrate lock-in thermography using nitrogen-vacancy centers in diamond nanoparticles. We successfully visualize thermal diffusion in glass coverslip and Teflon with micrometer resolution and deduce their thermal diffusivity. By spreading diamond nanoparticles over the sample surface, temperature variation can be measured directly without any physical contact, such as lead wires, making it possible to visualize the micrometer-scale thermal behavior of various materials.