Field-driven diffusion of transition metal and rare-earth ions in silicate glasses

The growing applications of glass-based photonic devices, like light waveguides and luminescent materials, demand the development of a versatile diffusion technique. Field-assisted solid-state ion diffusion is a novel technique developed for diffusing transition metal and rare-earth ions in silicate glasses. Due to the limitations of other conventional ion diffusion techniques in the case of multivalent ion diffusion, this technique serves to be equally suitable for the diffusion of both the monovalent and multivalent ions in the glass. In order to understand the mechanism of diffusion, thin films of Au/Er were deposited on soda-lime and borosilicate glass slides, and diffusion was established by applying an external electric field across the sample inside a furnace at a constant temperature. Alkali content of the glass was observed to deplete and the resulting vacancies were filled by the ions from the deposited film. The in-depth diffusion profiles of the doped-glasses were studied using secondary ion mass spectrometry and quantitative analysis was performed with Rutherford backscattering spectrometry. The optical absorption spectroscopy confirmed that the dopants were in non-precipitated form and transmission electron microscopy enabled direct observation of the size and distribution of the doped nanoparticles. The present results demonstrate that the diffusion depends on the processing conditions, glass composition and oxidation rate of the deposited film at the film-glass interface. The observed higher dopant concentration in the soda-lime silicate glass than the borosilicate glass may be due to the higher alkali content in the former glass. The diffusion of considerable amounts of Er content into the superficial layer of the glass, makes it suitable for telecommunication applications.