Au-Cu and Pd-Cu nanoclusters obtained by ion implantation in silica: stability under thermal annealing

We have investigated the effect of thermal annealing in reducing and oxidizing atmospheres on two systems, namely Pd + Cu and Au+Cu sequentially implanted silica. In the case of annealing in reducing atmosphere (4%H2 for 1h at 900\ub0C) the two systems undergo similar modification: dopant aggregation and increase of the size of the alloy clusters. When they are heated in air, the oxidation of the copper occurs in both cases, but while in the Au+Cu implanted silica the de-alloying process is completed after 1 h, in the Pd + Cu the alloy clusters are still present. The role of the alloy components in driving the structural modifications under heating is discussed