Experimental and Computational Investigations of Surface Polaritons at Metal‐Oxide‐Semiconductor Interfaces

Abstract

ABSTRACT Planar surface plasmon polaritons (SPPs) at metal–oxide–semiconductor (MOS) interfaces are central to plasmon‐assisted optoelectronic and tunneling devices, where ultrathin dielectrics govern field confinement and energy transfer. However, a direct link between electron energy‐loss spectroscopy (EELS) measurements and electromagnetic power dissipation at buried interfaces remains unclear. Here, we combine STEM–EELS with full‐wave electromagnetic simulations to investigate SPP excitation in planar and stacks with 10 nm dielectric spacers. Using a finite‐difference time‐domain approach, the fast electron is modeled as a broadband electromagnetic source, enabling decomposition of extinction into absorbed and scattered power and direct comparison with EEL spectra. We show that extinction is dominated by non‐radiative absorption, confirming that the observed resonances originate from SPPs confined to the buried Au–oxide interface. Increasing dielectric permittivity induces a redshift and modifies modal confinement, while losses remain Au‐dominated. Kramers–Kronig analysis and simulations further confirm dielectric dispersion effects and exponential evanescent decay across the oxide layer.