Self-Consistent Tip Conditioning for Tip-Enhanced Raman Spectroscopy in an Ambient Environment

Tip-enhanced Raman spectroscopy (TERS), which uses plasmons formed between the metallic tip and the sample upon laser irradiation, has emerged as a promising analytical method that is applicable in various environments. However, the practical use of TERS combined with scanning tunneling microscopy (STM) in an ambient environment has not reached its full potential thus far; this is because the atomic-scale geometry near the tip apex plays a crucial role in stable STM imaging, whereas plasmon enhancement for TERS is achieved on a submicron-scale tip structure, rendering it difficult to select an appropriate tip in advance. Herein, we propose a specific and simple method for tip conditioning that utilizes local heating through plasmon excitation in a self-consistent manner. This method is established on the basis of the characterizations of the tip shape and plasmonic properties. Accordingly, we demonstrate stable STM imaging compatible with reliable TERS measurements using the preconditioned tip.