Localized surface plasmons in structures with linear Au nanoantennas on a SiO₂/Si surface

The study of infrared absorption by linear gold nanoantennas fabricated on a Si surface with underlying SiO₂ layers of various thicknesses allowed the penetration depth of localized surface plasmons into SiO₂ to be determined. The value of the penetration depth derived experimentally (20 ± 10 nm) corresponds to that obtained from electromagnetic simulations (12.9-30.0 nm). Coupling between plasmonic excitations of gold nanoantennas and optical phonons in SiO₂ leads to the appearance of new plasmon-phonon modes observed in the infrared transmission spectra the frequencies of which are well predicted by the simulations.