Enhancing optical contrast of sub-wavelength optical image using graphene oxide coated probe in scanning thermal microscopy

Abstract

Scanning thermal microscopy (SThM) is a powerful technique for obtaining local thermal information on a sample surface using a nano-fabricated thermometer probe. One important application of SThM is sub-wavelength optical imaging, which captures the photothermal response of the probe to light. In this nano-scale imaging technique, optical contrast and spatial resolution are critical performance indicators. The size and material of the thermometer probe play a significant role in determining image quality, as a smaller radius can improve spatial resolution but reduce optical contrast and sensitivity due to decreased light absorption. To address this challenge, we have developed an approach to improve the photothermal energy conversion efficiency by coating the probe with atomically thin graphene oxide (GO). Our results demonstrate that this GO coating can enhance optical sensitivity by more than 1.5 times with linear optical power dependency. Importantly, the coating significantly improves the root mean square contrast of the image by 2.56 times without compromising spatial resolution. Our study highlights the potential of GO-coated probes to improve the sensitivity and quality of SThM-based sub-wavelength optical imaging.