Influence factors on tip radius and shape in electro-chemical etching for passive near-field microscope

Abstract

In recent years, we have developed a home-made passive Scanning Near-field Optical Microscope (SNOM) utilized to probe spontaneous emission from metals and dielectric materials. The evanescent waves generated on the sample surface are scattered by sharp tungsten tips made by electro-chemical etching. Previous study visualized that the spatial resolution of the passive SNOM have a strong relationship with the tip size. This research aims to stably fabricate tips within 20 nm by analysing the influence factors including solution concentration, voltage and cut off current in electro-chemical etching. By utilizing appropriate parameters in fabricating, it is expected to obtain sharp tips with good shape so that we can improve the spatial resolution of passive SNOM.