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[摘要]：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 degrees C; (10 Au films (7.5 and 10 nm nominal thickness) evaporated Oil unmodified glass and annealed 10 h at 550 or 600 degrees C, The 3 D 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 changes from Island coalescence and coarsening (low nominal thicknesses) to dewetting of percolated films (higher nominal thicknesses). The aspect ratio of more than 90% of the islands in annealed films is < 1.5; therefore, splitting of the SP band to transversal and longitudinal components is not observed. The bulk refractive index sensitivity (RIS), in terms of SP wavelength shift and plasmon intensity change (PIC) per refractive index unit (RIU) change of the medium, was determined by measuring UV-vis spectra of Au island films in a series of methanol/chloroform mixtures. The RIS values for SP wavelength shift (RIS lambda) and PIC (RISext) are 66-153 nm/RIU and 0.2-0.81 abs.u./RIU, respectively. The RIS shows a strong dependence oil the wavelength of the SP maximum extinction, i.e., a higher RIS is measured for Au island films exhibiting a SP band at longer wavelengths. Partial thermal embedding of the Au islands in the glass Substrate stabilizes the systems but lowers the RIS. The results presented may be useful for tuning the morphology and optical response or Au island films. |
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