Concurrently depostied Ag-Au alloyed nanoislands for wide-range plasmon resonance tuning

Abstract

Despite relatively recent discovery, vigorous research has been performed to apply localized surface plasmonic resonance (LSPR) in numerous fields of biophotonic applications such as surface enhanced Raman scattering and metal enhanced fluorescence. LSPR refers to electro-magnetic field enhancement of metallic nanoparticles when the wavelength of incident light matches the resonant frequency of the particle’s free electrons. However, naturally existing metals’ intrinsic properties, i.e., material’s permittivity and refractive index, set a limitation upon tuning range of plasmonic resonance wavelength. To overcome such limitation, recent works have reported studies on plasmonic resonance of bimetallic or metal alloy nano-structures. Yet, conventional methods on alloyed plasmonics incorporates e-beam lithography or dip-pen patterning in fabricating alloyed nanostructures, which are economically expensive and time-consuming methods that are not suitable for biophotonic applications. The objective of this research is to propose a novel method for visible range plasmonic resonance wavelength tuning of plasmonic nanostructures. Gold (Au) and silver (Ag) were used to fabrication metal alloy nanostructures for visible range resonance tuning, while solid-state dewetting method was utilized for wafer-level fabrication at a very low cost. Ag-Au alloyed nanoislands presented in this work provides a new insight in wide-range plasmonic resonance wavelengths tuning in the visible region that can potentially be used for numerous biophotonic applications such as SERS, PEF, and plasmonic color filters.