Observation of nanostructure by scanning near-field optical microscope with small sphere probe

摘要

Step and terrace structure has been observed in an area of 1?μm×1?μm on the cleaved surface of KCl–KBr solid-solution single crystal by scanning near-field optical microscope (SNOM) with a small sphere probe of 500?nm diameter. Lateral spatial resolution of the SNOM system was estimated to be 20?nm from the observation of step width and the scanning-step interval. Vertical spatial resolution was estimated to be 5–2?nm from the observation of step height and noise level of photomultiplier tube (PMT). With applying a dielectric dipole radiation model to the probe surface, the reason why such a high spatial resolution was obtained in spite of the 500?nm sphere probe, was understood as the effect of the near-field term appeared in the radiation field equations.