STUDY OF SHEAR FORCE AS A DISTANCE REGULATION MECHANISM FOR SCANNING NEAR-FIELD OPTICAL MICROSCOPY

Results of the investigation into the suitability of the shear-force d istance regulation mechanism for scanning near-field optical microscop y (SNOM) are presented. It is shown that there is a range of relative sizes of surface features to tip size that gives rise to malfunctions of the shear-force distance regulation mechanism. If the size of the t ip is comparable to the size of any depressions on the sample, the cor responding shear-force image may show contrast reversal. It is also sh own that the resolution obtained when imaging a surface with the shear -force scanning microscope may differ for the two perpendicular latera l directions. The resolution along the oscillation axis is usually low er than the one perpendicular to it. This has implications for SNOM im ages. Therefore, the interpretation of shear force, and hence SNOM ima ges, may become complex when imaging any sample with significant surfa ce roughness. (C) 1996 American Institute of Physics.