Development of cryogenic scattering-type thermal near-field microscope

Due to the lack of a nano-thermal imaging technique at low temperatures, we have developed a cryogenic scattering-type scanning near-field optical microscope (s-SNOM). The system mainly contains a highly sensitive long-wavelength infrared confocal optics and an AFM based on a piezoelectric tuning fork probe. By using the cryogenic s-SNOM, we have successfully detected the surface electromagnetic evanescent fields on a biased NiCr wire. The near-field signals originate from the thermally excited fluctuating charge of conduction electron. In the near future, we expect the s-SNOM enable to investigate kinetics energy of charge/phonon in non-equilibrium nano-devices.