The enhancement factor (EF) value is a parameter that quantifies the enhancement of the Raman signal by the enhanced electric field at the tip apex. It is based in the contrast value. The contrast value is calculated using the experimental data collected from the near-field scan and the far-field scan at the same point. Gold TERS probes guarantee a contrast higher than 20 and silver TERS probes higher than 40. These values lead to an enhancement factor up to 10⁵-10⁶ with Next-Tip TERS probes.

Silver TERS tips are protected with a second layer of gold nanoparticles to avoid oxidation and contamination, preserving the effect of plasmon. This dense gold nanoparticle coating guarantees a thicker layer of metal that significantly improves the durability of this type of probes. In addition, the irregularities formed by the nanoparticles along the tip surface extend its lifetime during the measurements (when it is heated, and hence smoothed by the Raman laser).

The great control over the coating process allows high resolution on robust probes with a high degree of reproducibility. Furthermore, this coating process enables the placement of one or two nanoparticles in the apex of the tip, achieving very high lateral resolution. Measurements show AFM resolution less than 5nm and TERS resolution less than 10nm.