China finds a clever way to measure extreme heat drops at nanoscale

Chinese researchers from Peking University have developed a novel method to measure heat flow at the atomic scale, overcoming longstanding challenges in observing interfacial thermal resistance between different materials. Using an advanced electron microscopy technique, they tracked how electrons lose energy when interacting with vibrating atoms (phonons), enabling them to visualize heat transfer across material boundaries with sub-nanometer resolution. Their custom device created a controlled heat flow between aluminum nitride (AlN) and silicon carbide (SiC), materials commonly used in high-power electronics, applying a steep temperature gradient of 180 K/μm. The team discovered a sharp temperature drop of 10–20 K occurring over just two nanometers at the interface, indicating thermal resistance 30 to 70 times greater than in the bulk materials. They also found that phonons near the interface were in a nonequilibrium state and did not follow the usual Bose-Einstein distribution, revealing that heat is not merely slowed but scattered and reshaped at these junctions.