Depth-resolved nanostructure and refractive index of borosilicate glass doped with Ag nanocrystals

We present an investigation of the Ag-nanocrystal depth profile as well as the corresponding refractive index depth profile of borosilicate glass that was first doped with Ag by Na⁺ ? Ag⁺ ion exchange and subsequently irradiated with 1 MeV Xe ions. By combining RBS, XPS, XE-AES, and transmission and reflection spectroscopy, we show unambiguously that the Ag nanocrystals are formed in a layer with a thickness (90 ± 20 nm) that is significantly smaller than the 1-MeV Xe range (340 nm). The effective refractive index for the highest Xe fluence is n = 2.1 + 0.8 i at the resonance wavelength (? = 430 nm). The implications for the integration of surface-plasmon-resonance-based functionalities in photonic devices based on the described fabrication method are discussed.