High chemical resistance and Raman enhancement in Ag/Al2O3 core-shell plasmonic nanostructures tailored by atomic layer deposition

Abstract

Abstract Atomic layer deposition (ALD) is a powerful technique with the capabilities of conformal deposition and precise thickness control of thin films up to atomic level. In this study, the advantages of ALD are exploited to fabricate plasmonic nanostructures with high chemical resistance and sensitivity. An ultrathin, highly conformal Al2O3 shell layer was deposited by ALD upon Ag nanoparticles for the preparation of Ag/Al2O3 core-shell plasmonic nanostructures. The Al2O3 shell effectively serves as an anti-corrosion protective layer for Ag nanoparticles against the detrimental environment because of its conformal step coverage, pinhole-free structure, and chemical inertness. The shape of the Ag nanoparticles turns into spherical-like particles after the ALD process. An enhancement factor as large as ∼106 of surface-enhanced Raman scattering (SERS) from Ag/Al2O3 core-shell plasmonic nanostructures is achieved, indicating that the plasmonic sensitivity of Ag nanoparticles is not significantly degraded by the ultrathin Al2O3 shell layer. The result demonstrates that the conformal protective layer prepared by ALD facilitates the practical use of plasmonic chips in a variety of applications.