Tip-Enhanced Spectroscopy at the Nanoscale: Its Practical Issues and Solutions

This chapter reviews a variety of tips reported so far and focus on the tip positioning stability issue. It provides a technique for real-time and in situ compensation of thermal and mechanical drifts in tip-enhanced Raman scattering (TERS) microscopy. The chapter describes an efficient and practical method to precisely set and stabilize a metallic tip in the focus spot on a nanometer scale. Precise adjustment of tip-position relative to the focus spot is crucial for stable TERS measurement. Since tip-enhancement is affected by the tip position inside of the tightly focused laser spot, nanoscale tip-positioning is required to gain efficient tip-enhancement. Same as many other scanning probe microscopies, TERS microscopy also suffers from thermal drift due to shrinkage or expansion of system under the ambient condition. The focus stabilization is crucial for microscopic/nanoscopic measurement at an interface, particularly when scanning a large surface area because there is always a certain amount of the mechanical tilt of the sample substrate.