Gold Microplates with Nano-through-Holes for Nano-Raman Analysis of Solid Surface

Raman spectroscopy is a powerful tool to analyze materials. The demand for analyzing materials in a smaller analytical region is increasing as technology advances. Tip-enhanced Raman spectroscopy (TERS) is an option. However, measuring the surface of three-dimensional bulk materials is quite challenging, since simultaneously excited micro-Raman signals hide the enhanced nano-Raman signals. In 2024, another approach of using a porous gold membrane was reported to dedicate solid surface analysis. However, this method, for example, sacrifices the lateral analytical spot size because nanopores distribute throughout the membrane. Here, 70-nm thick gold microplates with nano-through-holes in the center are fabricated. The gold microplates provide a smaller analytical spot because nano-through-holes are fabricated only in a spatially limited region. The microplates and the surrounding structures are clearly visible under optical microscopes. We moved gold microplates to another location on a silicon substrate using a manipulator and successfully demonstrated nano-Raman measurements of silicon surface via nano-through-holes. The finite-difference time-domain calculations confirmed that enhanced electric fields are available by the nano-through-holes and revealed that the nano-Raman signals come from the surface of silicon within a depth of 5.4 nm.