Annealing behavior and solid-state reactions of Pd–Ge alloy thin films

Solid-state reactions and amorphous Ge crystallization for various ratios of thickness (or composition) in Pd–Ge alloy thin films after annealing have been investigated by transmission electron microscopy. Besides polycrystalline Pd (p-Pd) and amorphous Ge (a-Ge), polycrystalline Pd2Ge (p-Pd2Ge) phase is also formed in as-evaporated films. During annealing at 250 °C, polycrystalline Pd2Ge and PdGe are formed. The experimental results indicate that the formation of Pd2Ge and PdGe compounds may be dominant at low annealing temperatures, and also affect amorphous Ge crystallization. The reactions are sensitively dependent on the annealing temperatures and the thickness ratio of Pd and Ge films. The reactions and amorphous Ge crystallization are mutually competitive in Pd–Ge alloy thin films.