Effect of the gold crystallinity on the enhanced luminescence signal of scanning probe tips in apertureless near-field optical microscopy.

Abstract

The effect of gold tip crystallinity on their spectral amplification characteristics, monitored through the luminescence enhanced by surface plasmon resonance (SPR), is investigated experimentally. As the tip radius increases, the grains composing polycrystalline tips become larger, resulting in a blueshift of the emission while a redshift of the SPR was predicted for monocrystalline gold. This reveals that the effect of the grain size, a parameter that has not been considered so far, is dominant over that of the tip radius. This study is significant to apertureless scanning near-field optical microscopy, where the gold tip emission defines the spectral antenna range.