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We demonstrate that scattering-type scanning near-field optical microscopy (s-SNOM) allows nanoscale-resolved imaging of objects below transparent surface layers at both visible and mid-infrared wavelengths. We show topography-free subsurface imaging at lambda=633 nm. At lambda=10.7 microm, gold islands buried 50 nm below a polymer surface are imaged with a lateral resolution 80 nm.
Taubner et al. (Sat,) studied this question.