NUMERICAL STUDY OF THE TIP-SAMPLE INTERACTION IN THE PHOTON SCANNING TUNNELING MICROSCOPE

The differential method was used to model the scanning of a tip above a given surface defect in the photon scanning tunneling microscope ill umination conditions. In order to estimate the influence of the tip-sa mple interaction, we consider two configurations. In the coupled confi guration, the computation is complete and takes into account the tip-s ample interaction. In the uncoupled configuration, we use an outgoing wave condition in order to forbid artificially the creation of a multi ple scattering system between the tip and the surface. We show that, s ince the observed sample is dielectric, the tip can be regarded as a p assive sensor even if the tip is coated with metal. We also investigat e the case of a metallic sample for the two classical TE and TM states of polarization of the incident plane wave.