Exploring the detection limits of infrared near-field microscopy regarding small buried structures and pushing them by exploiting superlens-related effects

Abstract

We present a study on subsurface imaging with an infrared scattering-type scanning near-field optical microscope (s-SNOM). The depth-limitation for the visibility of gold nanoparticles with a diameter of 50 nm under SiN is determined to about 50 nm. We first investigate spot size and signal strength concerning their particle-size dependence for a dielectric cover layer with positive permittivity. The experimental results are confirmed by model calculations and a comparison to TEM images. In the next step, we investigate spectroscopically also the regime of negative permittivity of the capping layer and its influence on lateral resolution and signal strength in experiment and simulations. The explanation of this observation combines subsurface imaging and superlensing, and shows up limitations of the latter regarding small structure sizes.

Polarization-dependent near-field phonon nanoscopy of oxides: SrTiO3, LiNbO3 , and PbZr0.2Ti0.8Wehmeier1, Lang2, Liu3 et al. 2019Phys. Rev. B265230View full textAdd to dashboardCite

“…24,30,91 ). The PZT film In contrast to far-field examinations, near-field measurements typically probe the sample volume up to a depth of about 100 nm, 33,96,97 resulting in negligible contributions of the STO substrate to the near-field signal of our 200-nm-thin PZT. 98 The near-field spectra of Figs.…”

Review of near-field optics and superlenses for sub-diffraction-limited nano-imaging

“…cap on a nanoelectronic device), provided that the imaginary part of the cap material permittivity is sufficiently small. 182 To avoid the need for a near-field readout of the image from a superlens, there has been work on other classes of sub-diffraction-limited lenses which function by converting evanescent modes into propagating modes. In 2006, a so-called "far-field superlens" (FSL) was first developed which added a grating structure to a metallic film as in Fig.…”

Subsurface chemical nanoidentification by nano-FTIR spectroscopy

“…Despite s-SNOM and nano-FTIR being surface scanning techniques, the finite penetration depth of near fields into the sample allows for subsurface probing of nanoscale structures and defects up to a depth of 100 nm [23][24][25][26][27] . For s-SNOM it has been also shown that depth-resolved information-with the potential of three-dimensional sample reconstruction-can be obtained by analysis of several higher harmonic signals, each of them having a different probing depth [28][29][30][31] .…”