Morphology and Refractive Index Sensitivity of Gold Island Films

Abstract

The growing interest in recent years in gold island films prepared by vapor deposition on transparent substrates is largely attributed to the prominent localized surface plasmon (SP) extinction associated with nanostructured metal films. In the present study, two types of evaporated Au island films were investigated: (i) Au films (2.5, 5.0, and 7.5 nm nominal thickness) evaporated on silanized glass and annealed 20 h at a temperature <250 °C; (ii) Au films (7.5 and 10 nm nominal thickness) evaporated on unmodified glass and annealed 10 h at 550 or 600 °C. The 3D morphology of the Au islands was analyzed using high-resolution scanning electron microscopy (HRSEM), cross-sectional transmission electron microscopy (TEM), and atomic force microscopy (AFM) cross-sectional profilometry. Annealing at high temperatures, close to the glass transition temperature of the substrate, results in wetting of the Au islands by the glass and partial island embedding. The mechanism of morphology evolution during annealing ch...