TEM observation of CuBr nanoparticles prepared by copper diffusion process in a glass matrix

Copper ions were incorporated into a borosilicate glass containing Br− ions by means of a conventional Cu-staining process. The Cu+ ions migrated to about 60 μm from the glass surface through diffusion in the staining at 510 °C for 48 h. The Cu+ ions reacted with Br− ions to form CuBr nanoparticles in this region. A transmission electron microscope observation along the depth revealed that the average particle size decreased with depth; from 5.5 nm at the surface to 3.9 nm at 60 μm in depth. These results were qualitatively consistent with the spectroscopic data previously reported in which the CuBr exciton peak at each depth shifted to higher energy with depth. The copper and CuBr concentration profiles along the depth were discussed from the viewpoint of the diffusion of copper ions and reversible precipitation reaction of CuBr from the Cu+ and Br− ion-supersaturated glass matrix.