Image resolution in reflection scanning near-field optical microscopy using shear-force feedback: Characterization with a spline and Fourier spectrum

Scanning near-field optical microscopes (SNOM's) actually lead to nanometric lateral resolution. A combination with shear-force feedback is sometimes used to keep the SNOM tip at a constant force from the sample. However, resolutions in shear-force and optical data are different. An estimation of both resolutions is important for characterizing the capabilities of such systems. The basic principle of the measurement is to compare a spline-fitted logarithm of the power spectra calculated with the optical image with that of the shear force image in which resolution is determined a. priori. Quantitative results are given in the case of periodic or untested sample and simulated data. Moreover the accuracy and the stability of the method are discussed. (C) 1997 Optical Society of America.