Berlin 2005 – scientific programme

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O: Oberflächenphysik

O 47: Rastersondentechniken III

O 47.2: Talk

Tuesday, March 8, 2005, 16:00–16:15, TU EB202

Scattering scanning near-field optical microscopy on anisotropic dielectrics — •Susanne Schneider, Stefan Grafström, and Lukas Eng — Institute of Applied Photophysics, University of Technology Dresden, D-01062 Dresden

Scattering scanning near-field optical microscopy (s-SNOM) is based on the interaction between an optically scattering nano-cluster (AFM tip) and a dielectric sample. The size of the cluster defines the resolution of the microscope, which is in the order of nanometers. On this scale the optically anisotropic properties of the sample have to be taken into account, even if the sample is isotropic on the macroscopic scale.

We discuss the interaction between a cluster and an anisotropic sample using an analytical dipole-dipole model by taking the following contrast mechanisms into account:

1. The reflection on the surface of the anisotropic sample, which causes a change in the external electric field at the position of the probe.

2. The modification of the polarizability of the tip by interaction with the anisotropic sample. Here we use the image charge method for anisotropic samples, which was developed in 1997 by I. Lindell.

3. The formation of a resulting dipole which is the superposition of the tip dipole and the image dipole induced in the sample.

In these calculations not only the influence of the sample anisotropy is included but also the anisotropy that the probe may exhibit for geometrical or material-specific reasons.