Cross-sectional TEM analyses of the as-deposited sample: (a) bright field image, (b) plasmon image (26 eV energy loss), and (c) nickel map (close to the nickel absorption edge at 855 eV). A thin amorphous layer is formed at the interface with silicon due to nickel diffusion into the substrate during deposition.
XRR profile of the as-deposited sample. The interfacial layer contains Ni and Si atoms in a concentration ratio between those of NiSi and , as sketched in the lower panel.
Plan view TEM analyses of the (a) as-deposited sample and (b) in situ annealed sample. A 5 min annealing at induces an amorphization process (large ring in the diffraction pattern) characterized by the formation of a network of white features in the image.
TEM analyses during further in situ heating. After 16 min at the amorphization process is completed. Increasing the temperature to induces a structural modification of the amorphous layer, characterized by the formation of very small features uniformly distributed all over the sample area.
Cross-sectional TEM analyses after 10 min annealing at : (a) bright field, (b) oxygen map, (c) silicon map, and (d) nickel map. A thick amorphous Ni–Si layer is formed at the end of the annealing process at , by complete consumption of the nickel supply. At , pyramidal and regularly spaced protrusions are formed at the interface between the amorphous layer and the substrate.
High resolution TEM image of the sample annealed at for 10 min. The facets of the protrusion follow (111) silicon planes.
XRR profile of the sample annealed at , compared to the corresponding data for the as-deposited layer. The electronic density of the amorphous layer is close to that of a NiSi layer, as sketched in the lower panel.
In situ TEM analyses after an additional 8 min annealing at . Large epitaxial grains are formed within the amorphous Ni–Si matrix.
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