The control of gold nanocluster sizes in dielectric thin films via ion beam assisted deposition

摘要

Gold nanoclusters in silica were deposited by co-evaporation of gold and silica in the presence of an argon ion beam. Gold clusters are formed in-situ during the deposition process. The damage induced by the ion beam controls the cluster size, and clusters with a diameter between 15 - 30 A are obtained. The Au clusters show a highly compressive strain as measured by X-ray diffraction and lattice parameters up to 3.5 % smaller than in bulk gold are observed. Post-deposition annealing in air leads to cluster growth and release of the strain. Annealing near the melting point of gold causes the clusters to grow exponentially up to 180 A. This is accompanied by a blue shift of the Mie absorption peak. Furthermore the formation of a superlattiee was observed by TEM and confirmed by small angle XRD measurements.