Copper-based nanocluster composite silica films by rf-sputtering deposition

Prescribed nanocluster composite glass features require the control of the cluster formation and growth, and therefore the definition of effective preparation protocols. In this work, copper-containing silica films were synthesized by sputtering co-deposition of copper and silica in a radiofrequency magnetron sputtering apparatus. The composite system was sequentially thermally-treated in different annealing environment (oxidizing and/or reducing). Characterization of samples along the various preparation steps was performed by Rutherford backscattering spectrometry, X-ray diffraction, and optical absorption spectroscopy. The copper behavior during the composite formation was complex: copper migration and aggregation depend critically on the annealing conditions, and quite different stable structures actually result, such as fcc Cu and/or monoclinic CuO nanoparticles.