Ni silicide nanowires analysis by atom probe tomography

• Two methods of NW preparation have been proposed for NWs analysis by APT.
• These methods were tested and reconstructed volumes for different kind of NWs.
• Ni silicide formed on Si nanowire has been analyzed by atom probe tomography.
• δ-Ni2Si is the only phase formed on Si NW and substrate after 200 °C during 1 h.
• Au is localized at Ni/silicide interface after silicidation suggesting Ni diffusion.

The Ni silicide formed at low temperature on Si nanowire has been analyzed by atom probe tomography (APT) thanks to a special technique for sample preparation. A method of preparation has been developed using the focused ion beam (FIB) for the APT analysis of nanowires (NWs). This method allow for the measurement of the radial distribution when a NW is cut, buried in a protective metal matrix, and finally mounted on the APT support post. This method was used for phosphorous doped Si NWs with or without a silicide shell, and allows obtaining the concentration and distribution of chemical elements in three-dimensions (3D) in the radial direction of the NWs. The distribution of atoms in the NWs has been measured including dopants and Au contamination. These measurements show that δ-Ni2Si phase is formed on Si NW, Au is found as cluster at the Ni/δ-Ni2Si interface and P is segregated at the δ-Ni2Si/ Si NW interface. The results obtained on NWs after silicidation were compared with the silicide on the Si substrate, showing that the same silicide phase δ-Ni2Si formed in both cases (NWs and substrate).

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