Formation of epitaxial metastable NiGe2 thin film on Ge(100) by pulsed excimer laser anneal

Epitaxial nickel digermanide (NiGe2), a metastable phase, was formed by laser annealing Ni on (100) germanium-on-silicon substrates. The NiGe2 formation was investigated using transmission electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffraction, Rutherford backscattering spectroscopy, and first-principles calculations. The formation mechanism of NiGe2 is discussed and is attributed to both the reduced interfacial energy at the NiGe2/Ge(100) interface and the kinetic aspects of the laser annealing reaction associated with phase transformation and film agglomeration.