Keywords:tip-enhanced Raman spectroscopy, NSOM
Gap-mode tip-enhanced Raman spectroscopy (TERS) is a powerful nano-analytical technique, in which the plasmonically enhanced light field at the junction between a metallic tip and a metallic substrate excites Raman scattering from a tiny volume of a sample. A scanning tunneling microscopy (STM) is usually used for the gap-mode TERS since the STM-based TERS inherently works in the gap-mode configuration and constantly produces high signal enhancement. In contrast, the cantilever-based atomic force microscopy(AFM) approach has different advantages over STM-based TERS, such as less intrinsic sample limitations and versatile imaging modes in air or even liquid environment, so that a unique and correlative analysis is accessible with AFM-TERS. Nevertheless, AFM-based TERS is still not very common because conventional granular tips used in AFM-based TERS do not provide reproducible enhancement because of random arrangement of metallic grains on tips. Although some other methods, such as employing electrodeposition and attaching a silver nanowire produce plasmonically active TERS tips in a reproducible way, they require optimal procedures to fabricate tips, which is still not feasible for everyone. In this talk, a simplistic and cost-effective fabrication method of reproducible metal-coated cantilever tips for gap-mode TERS measurement will be discussed. Our tip design, which we called a “one-side metal coated tip”, consists of an oxidized silicon body structure in a pyramidal shape and a smooth silver layer on one surface of the pyramidal structure. The plasmonic hot-spot is generated at the junction between the plasmonic tip and the gold thin film. We demonstrated that fabricated plasmonics tips provided signal enhancement of the Raman signal from standard samples on a gold thin film with virtually 100% reproducibility.