Optical Properties of Plasmon-Tunable Tip Pyramids for Tip-Enhanced Raman Spectroscopy

For tip-enhanced Raman spectroscopy (TERS), the recently developed plasmon-tunable tip pyramid, composed of a gold micropyramidal body with a nanopyramid end, makes it possible to obtain spectral enhancements in 2D systems up to two orders of magnitude higher than what is found in the literature. Herein, the optical properties of these tips are explored, including the field-enhancement dependence on nanopyramid edge length (L), its apex diameter (D), tip-sample distance (Z), and the presence of a metallic micropyramid body. The study shown herein rationalizes the optical properties of these tips, important for understanding the related TERS results.