Using a tetrahedral tip as a probe, it is possible to combine the techniques of scanning tunneling microscopy (STM) and scanning near-field optical microscopy (SNOM) in the same probe tip so that the probing of the respective near-field interactions occurs virtually at the same spot of the tip. Atomic resolution on pyrolytic graphite and stable images on rough samples are routinely obtained in the STM mode. In the combined SNOM/STM mode, an absorption contrast in the optical image is obtained with images of evaporated silver films on glass as well as of silver deposited on an indium tin oxide substrate. We obtained a point-to-point resolution of 6 nm, whereas the edge resolution is about 1 nm.
"Scanning near-field optical microscopy with a tetrahedral tip at a resolution of 6 nm," Journal of Biomedical Optics 1(1), (2 January 1996). https://doi.org/10.1117/12.227700