Ion beam-treated silicon probes operated in transmission and cross-polarized reflection mode near-infrared scanning near-field optical microscopy (NIR-SNOM)

We present aperture probes based on non-contact silicon atomic force micros copy (AFM) cantilevers for simultaneous AFM and near-infrared scanning near -field optical microscopy (SNOM), For use in high-resolution nearfield opti cal microscopy, conventional AFM cantilevers are modified by covering their tip side with an aluminium layer to obtain an opaque coating. To fabricate an aperture, this metal layer is opened at the very end of the polyhedral probe using focused ion beams, thus allowing apertures of <200 nm in diamet er to be created. We describe our concept and investigate the characteristi cs of these probes by discussing images in transmission and cross-polarized internal reflection mode. Apart from probe characterization, our attention is devoted to the dependence of both signal amplitude and resolution on th e tip-to-sample distance and to the polarization effects observed in the co urse of these investigations. To exclude artefacts induced by distance cont rol, the measurements analysed here are performed in constant-height mode. Copyright (C) 1999 John Wiley & Sons, Ltd.