Low-Temperature Preparation of High-Temperature Nickel Germanides Using Multilayer Reactants

Nickel germanide thin films were prepared using nickel−germanium multilayers as reactive precursors. Over the composition range x Ni = 0.24−0.42, high-temperature germanides (δ-Ni 5 Ge 2, ε-Ni 5 Ge 3, and Ni 3 Ge 2 ) form under conditions where the phases are thermodynamically unstable. δ-Ni 5 Ge 2 forms over a broader range of composition than has been observed previously. The three high-temperature phases accessible by this synthetic route are observed to share related structure types, which are related to the structure of amorphous nickel germanium alloys with similar composition. The ability to selectively prepare metastable phases under mild conditions has important implications with respect to the search for new materials for use in integrated devices.