Light-driven nanoperiodical modulation of alkaline cation distribution inside sodium silicate glass

Chemical differentiation of atoms in the nanoscale by femtosecond laser treatment enabling the formation of periodical nanostuctures (nanogratings) is demonstrated for the first time in sodium silicate glass. We report periodical redistribution of Na+ cations in SiO2 matrix related to the formation of nanogratings in 15Na2O·85SiO2 glass. They are shown to be similar to nanogratings in silica glass but their inscription is a much longer process taking 105-107 laser pulses. SEM, TEM and EDXA analysis revealed substantial migration of Na+ from the laser-irradiated area. Na+ cations remaining in nanogratings are accumulated at the boundaries or inside the 20-30 nm thick nanoplanes whereas the chemical composition of regions between the nanoplanes approaches to pure SiO2 making a drastic chemical differentiation on a nanoscale. Thus, the opportunity of optically driven nanoperiodical modulation of alkaline cation distribution inside the glass changing its properties in the nanoscale has been shown. This cation redistribution is expected to stimulate the search for new approaches to the design of complex nanostructured architectures in a glassy matrix.