Papers by Author: M. Rosenbluh

Abstract: In the course of reactive diffusion of hydrogen in metal-doped glasses, at some conditions, metallic nanoparticles grow forming quasi-periodic layered structure. We have developed a model defining conditions necessary for the formation of the layered structures. The model indicates relatively narrow range of parameters providing the quasi-periodic growth of the nanoparticles. The layered structure arises at relatively low over-saturation by neutral metal in the diffusion zone, due to the competition of two processes: enrichment of the glass by neutral metal atoms via reducing of metal ions by diffusing hydrogen and depletion of the glass by the metal atoms caused their diffusion to the nanoparticles. The model can be also applied to other situations where reactive diffusion inducing the formation and growth of nanoparticles occurs.

Abstract: Annealing in a hydrogen atmosphere of silicate glass plates doped by Ag+ ions leads to the reduction of silver to a metallic state (Ag0) and to the formation of silver nanoclusters. The kinetics of clustering during hydrogen diffusion into the glass and diffusion of Ag0 atoms in the glass matrix have been studied in a temperature ranging from 160 to 200oC by SEM, AFM and optical spectrometry. The absorption spectra have a peak near 410 nm corresponding to the surface plasmon resonance in Ag clusters. The position of the peak moves as the clusters grow. A theoretical analysis of the absorption spectra allowed us to estimate the cluster size as a function of time, as well as the thickness of the layer filled by clusters, which also changes with time. From AFM data we could measure the kinetics of cluster growth on the surface. We have theoretically analyzed the kinetics of cluster growth during reactive hydrogen diffusion, the kinetics of bulk cluster growth, surface cluster growth, and thickening of the layer filled by clusters.

Abstract: Two types of silver-doped glass were used for direct laser recording of 2D and 3D photonic crystals. The first contained a diffusion layer (20 microns thick) with embedded silver nanoclusters of 20-nm average radius. 2D and 3D photonic crystals of submicron lattice parameters were fabricated by nanosecond pulsed laser irradiation (l, = 355 nm) using four or five coherent intersecting beams. Under irradiation the clusters absorbing light energy are heated to high temperatures and become mobile due to the formation of liquid shells around them. Adjacent clusters move towards each other and towards the irradiated surface under local temperature gradients, form agglomerates and merge in periodically located "spots" of high light intensity in the interference field. The second type of glass, photosensitive to UV irradiation, contained in the bulk Ag+ and Ce3+ ions. Under UV irradiation excited electrons passed from Ce3+ to Ag+. The Ag atoms became neutral and under subsequent heat treatment of the glass at elevated temperatures have a tendency to form nanoclusters, thus “developing” the UV recorded patterns. Using nanosecond pulsed irradiation of 308 nm we have recorded 3D photonic crystals in the bulk of such glass.