Critical Factors in Cantilever Near-Field Scanning Optical Microscopy

An important technique for high resolution optical imaging, beyond the diffraction limit, of nanostructured surfaces is aperture near-field scanning optical microscopy (NSOM). Even though NSOM has already demonstrated its good performance in a number of different applications, its quantitative application is still a challenge, due to a number of factors, which commonly influence the quality of the measurement output and consequently extrapolation of quantitative parameters. In this paper, a systematic study is reported, analyzing the effect of the most critical factors in cantilever NSOM measurements, with particular attention to tip geometry and aperture, scanning configuration, and scan mode. Investigations have been carried out on a commercial instrument, in combination with reference standard for NSOM calibration (as for instance the Fisher pattern) and other samples opportunely produced for this paper.