title: Nanoscale-resolved subsurface imaging by scattering-type near-field optical microscopy.
abstract: 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 < 120 nm, corresponding to lambda/90. Studying oxide layers with systematically varied thicknesses we provide experimental evidence of mid-infrared near-field probing in depths > 80 nm.
authors.forename: Thomas
authors.initials: T
authors.lastname: Taubner
authors.forename: F
authors.initials: F
authors.lastname: Keilmann
authors.forename: R
authors.initials: R
authors.lastname: Hillenbrand