Nickel monosilicide can be prepared by depositing a nickel layer on silicon and subsequent annealing. In the case of Ni films with thicknesses above 4 nm, the normal phase transition is given by NiSi at 250 °C followed by NiSi at 350 °C and NiSi at approximately 800 °C. For films with an initial Ni thickness below 4 nm a direct transition from orthorhombic NiSi to epitaxial NiSi, skipping the nickel monosilicide phase, is observed.