ANNEALING BEHAVIOR OF PD A-GE BILAYER FILMS

Solid-state reaction and crystallization in Pd/a-Ge bilayer films of v arious ratios of thickness (or composition) after annealing have been investigated by transmission electron microscopy. Besides polycrystall ine Pd and amorphous Ge, the Pd2Ge phase is formed in as-evaporated fi lms with 54 and 67 at % of Ge. During annealing at 250-degrees-C Pd2Ge and PdGe are formed. During annealing at 350-degrees-C, besides the f ormation of Pd2Ge and PdGe, crystallization of amorphous Ge takes plac e, inducing fractal-like structures with a size of about 1 mum. The fr actal dimension varies from 1.60 to 1.88, depending on the composition of the films. The fractal formation can be explained by a random succ essive nucleation model.