Scanning-tunneling optical microscopy: a theoretical macroscopic approach

Abstract

A theoretical model for calculating the images obtained in scanning-tunneling optical microscopy is proposed. We calculate the intensity detected by a small spherical tip above a regular glass lattice illuminated in total internal reflection. The model is based on a macroscopic approach. We show that the resolution is limited neither by the wavelength nor by the decay length of the evanescent wave but that it is determined by the tip–sample distance and by the signal-to-noise ratio. We also discuss the quality of the images. In general, the intensity profile does not reproduce the sample profile. We analyzed two kinds of filtering that can deform the true profile. We also show that for a small sample period a strong signal is obtained only in TM polarization.