Versatile scanning near-field optical microscope for material science applications

We describe an aperture emission mode scanning near-field optical microscope (SNOM), optimized for material surface science applications. This instrument can be operated in both transmission and reflection configurations, in order to investigate transparent as well as opaque samples. It employs optical shear-force detection for tip/sample distance control, designed to minimize interference with the probe light. The SNOM head has been fully integrated on a homemade atomic force microscope platform and is placed in a controlled atmosphere chamber for reduction of surface contaminants. Within the compactness and the versatility obtained in our instrument, we have been able to optically discriminate different materials with a lambda/20 lateral resolution, and to distinguish polymeric aggregates, without damaging the surface, in spite of their rather poor optical contrast.