Silicide formation during reaction between Ni ultra-thin films and Si(0 0 1) substrates

• Thin films of Ni were deposited on silicon substrates and annealed up to 500 °C.
• Silicidation of the films was followed by in situ X-ray diffraction.
• Silicides were analysed by atomic probe tomography and electron microscopy.
• The NiSi phase was evidenced at low temperature in the thinnest film (3 nm).
• The NiSi grains grow in axiotaxy on the (0 0 1)Si substrate.

Silicidation of Ni ultra-thin films on Si(0 0 1) substrates was investigated from room temperature to 500 °C. In situ X-ray diffraction (XRD) experiments were performed to follow the reaction evolution. Transmission electron microscopy (TEM) and atomic probe tomography (APT) analyses highlight the formation of NiSi at low temperature (200 °C). A peculiar phase sequence is evidenced for the thinnest deposited Ni film for which the NiSi phase forms from the low temperatures. Structural analyses of the formed silicides indicate that the NiSi phase grows in axiotaxy with the substrate at 200 °C whereas NiSi2 rods form at higher temperatures.