Annealing behavior of silver, copper, and silver-copper nanoclusters in a silica matrix synthesized by the sol-gel technique

Silver, copper, and mixed silver-copper nanocluster-doped silica thin layers were prepared by the sol-gel process. Samples were heat treated in different annealing atmospheres (air, argon, or 5%c H-2-95%N-2) in the temperature range 500-1100 degrees C. Specimens were characterized by optical absorption spectroscopy, Rutherford backscattering spectrometry, x-ray diffraction, and transmission electron microscopy. Cluster growth and dissolution, as well as migration of metal atoms towards the sample surface, with a subsequent evaporation, were observed to occur at temperatures that depend on the annealing atmosphere. In the mixed silver-copper system, the formation of Ag-Cu phase-separated clusters was observed.