Tunable Localized Plasmon Transducers Prepared by Thermal Dewetting of Percolated Evaporated Gold Films

Abstract

Gold island films displaying localized plasmon properties were prepared by evaporation of just-percolated Au films onto glass substrates followed by annealing at ≥550 °C. Annealing induces depercolation and formation of large, single-crystalline, well-separated islands, partially embedded in the glass. Two dewetting mechanisms were identified, depending on the initial film morphology. The variability of island sizes and shapes provides effective means of tuning the position of the localized surface plasmon resonance (LSPR) band in a wide wavelength range. With an increase in the Au nominal thickness a transition occurs from transducers dominated by absorbance to ones dominated by scattering. Numerical simulations taking into account the shape and size distribution in actual island samples are in agreement with the experimental spectra. Refractive index sensitivity (RIS) measurements at a constant wavelength or at a constant extinction, tailored to the specific transducer, provide superior sensitivity to refractive index change, up to ca. 600 nm RIU–1 in wavelength shift.