We investigate the nanogap and polarization-resolved excitation of gap plasmon modes using terrace-stepped hexagonal boron nitride (hBN) sandwiched between Ag nanowires and Au substrates for a metal–insulator–metal gap structure. The gap plasmon modes in the proposed hybrid structure are dominantly excited by a P-polarized incident light, which is supported by full-wave numerical simulations. Plasmon mode evolution for various hBN spacer thicknesses ranging from 5 to 90 nm shows that optical signals acquired via unpolarized dark-field mapping spectroscopy are primarily due to the optical scattering of the P-polarized incident light. Moreover, this plasmonic mode changes significantly from gap plasmon mode to Fabry–Perot-type resonance in a hBN thickness of 50–90 nm. Our analysis reveals that the proposed hybrid structure based on Ag nanowires and stepped hBN provides a well-defined gap thickness and is a robust platform for analyzing gap plasmon modes.

我们使用夹在 Ag 纳米线和 Au 衬底之间的阶梯阶梯式六方氮化硼 (hBN) 来研究间隙等离子体模式的纳米间隙和极化分辨激发，以形成金属-绝缘体-金属间隙结构。所提出的混合结构中的间隙等离子体模式主要由 P 偏振入射光激发，这得到了全波数值模拟的支持。从 5 到 90 nm 的各种 hBN 间隔层厚度的等离子体模式演化表明，通过非偏振暗场映射光谱获得的光信号主要是由于 P 偏振入射光的光学散射。此外，这种等离子体模式在 hBN 厚度为 50-90 nm 时从间隙等离子体模式显着改变为法布里-珀罗型共振。