Fabrication of a pencil-shaped fiber probe with a nanometric protrusion from a metal film for near-field optical microscopy.

We propose a method to fabricate a probe with a nanometric protrusion for near-field optical microscopy. The method involves tapering process based on selective etching of an GeO2 doped fiber in buffered hydrogen fluoride solution and metallizing process by vacuum evaporation and chemical polishing. We obtained the tapered probe having a protrusion emerged from a metal film. The protrusion has an apex diameter less than 10nm and a foot diameter less than 20nm. Employing the probe, we succeeded in obtaining a highly spatially resolved image of 20nm sized gold particles.