Berlin 2015 – scientific programme
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O: Fachverband Oberflächenphysik
O 29: Near-Field Microscopy
O 29.1: Talk
Tuesday, March 17, 2015, 14:00–14:15, MA 042
λ/30 Lateral Resolution in Subsurface Imaging with an Infrared Near-Field Microscope — •Lena Jung, Benedikt Hauer, and Thomas Taubner — I. Institute of Physics (IA), RWTH Aachen University, 52056 Aachen, Germany
In scattering-type scanning near-field optical microscopy (s-SNOM), optical near-fields at the apex of a sharp illuminated tip are used for an investigation of the optical properties of the sample material with high spatial resolution. Since near-fields penetrate into a dielectric sample, non-destructive imaging of subsurface structures under thin layers of dielectrics is possible [1]. This capability provides a useful tool in the field of nanotechnologies, since nano-electronic devices are often covered by thin dielectric capping layers such as e.g. SiO2 or Si3N4.
The visibility of gold nanoparticles under a Si3N4-membrane in dependence of its thickness is investigated as well as the lateral resolution and signal contrast for different sizes of particles. A comparison to transmission electron microscopy (TEM) images of the same sample region enables a direct correlation between the nanostructures and the optical signals. The experimental results are confirmed by model calculations.
A spectroscopic investigation reveals a significant change in the lateral resolution due to the actual value of the dielectric function. Achievable is a resolution down to λ/30 for mid-infrared light. We observe minima at specific wavelengths and correlate these to the optical properties of the capping material and the so called superlensing effect.
[1] Taubner et al., Opt. Express 13, 8893 (2005).