Substrate and coverage engineered visible-range Fano resonance in SiO₂@C core-shell nanoparticles.

Area of Science:

• Nanophotonics and light-matter interactions
• Dielectric core-shell nanoparticles
• Plasmonics

Background:

• Fano-like resonance in dielectric nanoparticles is key for light-matter interactions.
• The influence of surface coverage and substrate on NP aggregation and optical response is not fully understood.

Purpose of the Study:

• To investigate the optical responses of SiO2@C core-shell NP films on different substrates.
• To explore the role of surface coverage-dependent aggregation in substrate-mediated Fano-like resonance.

Main Methods:

• Spectroscopic ellipsometry and critical-point analysis were used to study NP films on Cu, Si, and fused quartz substrates.
• COMSOL simulations were employed to analyze the electromagnetic field distributions and contributions of different multipoles.

Main Results:

• On Cu substrates, increasing NP coverage led to interconnected networks and visible-range Fano-like resonance via Mie-plasmon coupling.
• On Si substrates, large-area films suppressed resonance due to reduced scattering heterogeneity and dominant substrate electronic transitions.
• COMSOL simulations confirmed that larger clusters enhance magnetic quadrupole contributions, correlating with experimental observations.

Conclusions:

• Substrate properties critically modulate Fano-like resonance in dielectric core-shell NPs.
• Surface coverage and aggregation behavior dictate the emergence and characteristics of Fano resonance.
• Findings offer insights for designing NPs for tunable light-harvesting and nanophotonic applications.