Amorphous and metastable phases formation in Au-Ge bilayers by ion beam mixing

Abstract
Amorphous alloys have been produced by Ar+ beam irradiation of Au-Ge thin-film bilayers. Two different average compositions have been detected for implantation at 80 or at 300 K, respectively. Each amorphous phase decomposes into a crystalline one after aging at room temperature for several hours. The composition and structure of such crystalline phases are also controlled by the irradiation temperature. Prolonged annealing at 45 °C produces precipitation of pure Au and Ge respectively. The metastable crystalline phase formed at LN2T irradiation is tetragonal and has a composition range close to the χ phase formed after splat cooling technique. The room temperature phase has instead an hexagonal structure.