Reproducible electrochemical etching for plasmonic silver tip fabrication using a fast cut-off circuit

Plasmonic tips are a critical determinant of the performance of tip-enhanced Raman spectroscopy (TERS), making the reliable fabrication of tips with high enhancement factors an enduring challenge. Among noble metals, silver offers particularly strong electromagnetic field enhancement due to the large imaginary part of its dielectric constant. However, the low yield strength and high chemical reactivity of silver make the electrochemical etching process susceptible to over-etching, resulting in significant tip diameter variations and reduced fabrication reproducibility. In this study, we develop a control circuit capable of terminating the etching process within ∼50 ns, effectively suppressing over-etching during tip fabrication. In addition, plasmonic silver tips are fabricated via DC electrochemical etching using the control circuit. Furthermore, systematic etching experiments are performed by varying parameters such as etchant concentration and etching voltage, and the resulting silver tips are evaluated in terms of their fabrication yield and enhancement factor. Our approach enables the reproducible fabrication of high-quality silver plasmonic tips and provides practical guidelines for optimizing etching conditions, offering a robust pathway toward more reliable and routine TERS measurements.