Silver nanocluster formation in ion-exchanged waveguides: processing technique and phenomenological model

Silver-containing light waveguides, formed by ion-exchange process in glasses containing alkali oxides, were annealed in hydrogen atmosphere at temperatures in the range 150-250 degrees C. The processing technique causes silver atom precipitation to form nanometer-size clusters with similar to 2-10 nm distribution in sizes and a spatial distribution. The composites were measured by transmission electron microscopy, optical spectroscopies, m-lines technique, Rutherford backscattering energies, elastic recoil detection analysis and secondary ion mass spectrometry. The nano-sized cluster formation, accompanied by silver and sodium interdiffusion processes, after hydrogen permeation in the matrix, is not simply ascribed to a direct interaction with hydrogen, but to a more complex process involving a charge balancing mechanism during ion transport phenomena. Such a process is discussed in terms of a phenomenological model. Nonlinear refractive indices of some samples were measured.