Shape transition and migration of TiSi<inf>2</inf> nanostructures embedded in a Si matrix
Contributors: Anderson Sunday-Meya, David J. Smith, and Robert J. Nemanich
ABSTRACT
This study establishes that under conditions of epitaxial Si deposition, embedded Ti-silicide nanostructures undergo shape transitions and migrate upward to the surface during capping with a thin epitaxial Si layer. Many of these structures display a near-hemispherical shape which is attributed to minimization of their surface and interface energies. The density and size of the nanostructures are observed to be temperature-dependent. The buried islands induce inhomogeneous stress profiles on the capping layer surface. Atomic-force micrographs of the islands show square holes at the surface aligned along [110] directions which suggests that the sloping surfaces of the pits approximate to (111) surfaces, and the silicide interface is also facetted to match Si (111) planes. Cross-sectional electron micrographs reveal that many islands display faceting. The observed structural changes can be rationalized in terms of the interplay between thermodynamics and kinetics, solid-state capillarity, and the roughening transition.