Observation of enhanced heat transfer between a nanotip and substrate at nanoscale distances via direct temperature probing with Raman spectroscopy

Nanoscale heat transfer between two nanostructured surfaces holds paramount significance in the realms of extreme manufacturing and high-density data storage. However, experimental probing of heat transfer encounters significant challenges, primarily due to limitations in current instrumentation. Here, we report a method based on Raman spectroscopy to directly probe the temperature difference between a Si nanotip and SiC substrate. Results indicate a decrease in substrate temperature, while the temperature of the nanotip remains relatively stable as the nanotip moves away from the substrate from approximately 82.5 to 1320 nm. We trace this enhanced heat transfer to a significant augmentation, by one order of magnitude, in air conduction and thermal radiation energy exchange theoretically, with air conduction being the dominant mode over thermal radiation. This work advances the direct observation of surface temperatures with gaps smaller than 1 μm, utilizing a noncontact and nondestructive Raman technique, which can be extended to studying near-field heat transfer across various Raman-active surfaces.