DC electric field assisted fabrication and optical analysis of silver-doped nanocomposite glass

Embedded silver nanoparticles in glasses have raised a wide interest recently. One fabrication technique for these, which is used in this combination only in recent years, is by using field-assisted ion exchange from a metallic silver film, followed by annealing in air atmosphere. The first step results in a layer in the glass containing silver ions, while the annealing step leads to the reduction of silver to atoms followed by their agglomeration to nanoparticles. We present an analysis of the process of particle formation during the annealing step. Glasses were annealed for different durations, and thin slices of these glasses were made. Optical transmission spectra were measured, showing the position and shape of the surface plasmon bands of the nanoparticles. This allowed determining profiles of particle filling factors and sizes.The commercial crown glass B270 from Schott is used as a substrate. A silver film acts as the ion source and positive electrode. It is formed from a suspension of silver flakes in isopropanol [1]. The ion exchange is done inside an oven at 300°C with a voltage of 1000V applied for 1h. Afterwards the sample was cut into five pieces, which were annealed in air at 550°C, each for a different duration (1h, 2h, 4h, 8h, 48h). This resulted in the formation of silver nanoparticles (fig. 1a).From each sample a thin slice of the cross section was prepared (fig. 1b). These are showing the profile of the nanoparticles-containing layer. Transmission spectra of these were measured every 1.5µm with a microscope spectrometer (fig. 1c). The spectra of the nanoparticles were simulated using the Maxwell Garnett effective medium theory, delivering an effective dielectric constant for a composite medium from the dielectric functions of the components and their volume fractions. The dielectric function of the silver nanoparticles was calculated using the Drude model. The influence of the silver nanoparticles- was taken into count by a size-dependent dampening constant [2]. This allowed determining particle sizes and volume filling factors.