'Coreless defects' and the continuity of epitaxial NiSi sub 2/ Si(100) thin films.

Epitaxial thin films of NiSi sub 2 on Si(100) have been grown by room temperature deposition of Ni followed by a high temperature reaction. Initial stages of epitaxy revealed by transmission electron microscopy show nucleation of crystallographically equivalent islands related by a translation vector a/4 via the underlying silicon substrate. Coalescence of islands thus requires the generation of a/4 dislocations which is energetically unfavorable. We find that very thin films (~60angstroms) do not coalesce but choose to remain as islands leaving trenches of exposed substrate ~15angstrom in width between them. We propose that the trench left between islands can be described as a coreless defect in the silicide.