The interfacial reaction of Ni with Si, Si₀.₇₅Ge₀.₂₅, and Ge at 400°C has been investigated. A uniform epitaxial NiSi film was obtained at 400°C for Ni-Silicidation on Si using rapid thermal annealing method. Similarly, uniform film of NiGe was formed at 400°C for Ni reaction with Ge. Whereas using in situ annealing at 400°C, Ni₃Ge₂ and NiGe were observed. For the interfacial reaction of Ni with relaxed Si₀.₇₅Ge₀.₂₅ films rapid thermal annealed at 400°C, a mixed layer consisting of Ni₃(Si₁₋xGex)₂, Ni(Si₁₋yGey), and Si₁₋zGez (z>y>x) was formed; whereas only Ni₃(Si₁₋xGex)₂ and Ni(Si₁₋yGey>) were observed by in situ annealing. / Singapore-MIT Alliance (SMA)