title: Enhanced resolution in subsurface near-field optical microscopy.
abstract: We report an experimental analysis of the capabilities of scattering-type scanning near-field optical microscopy for mapping sub-surface features at varying depths. For the first time, we demonstrate experimentally that both the spatial resolution and depth contrast can be improved in subsurface microscopy by demodulating the measured near-field signal at higher harmonics of the probe's tapping frequency and by operating at smaller tapping amplitudes. Our findings are qualitatively supported by a simple dipole model.
authors.affiliation: CIC nanoGUNE Consolider, E-20018, Donostia-San Sebastián, Spain.
authors.forename: Roman
authors.initials: R
authors.lastname: Krutokhvostov
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Govyadinov
authors.forename: Johannes M
authors.initials: JM
authors.lastname: Stiegler
authors.forename: Florian
authors.initials: F
authors.lastname: Huth
authors.forename: Andrey
authors.initials: A
authors.lastname: Chuvilin
authors.forename: P Scott
authors.initials: PS
authors.lastname: Carney
authors.forename: Rainer
authors.initials: R
authors.lastname: Hillenbrand
mesh_terms: D000465:Algorithms; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008853:Microscopy / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity