Structural characterization of Ni₂Si pseudoepitaxial transrotational structures on [001] Si

The formation of pseudoepitaxial transrotational structures has been observed during the early stage of the reaction of thin Ni layers on [001] Si substrates. During the reaction, large Ni₂Si domains, characterized by single bending contours, establish a close relationship with the silicon lattice. The silicide domain consists of a core region, along the bending contour, where the silicide layer has grown epitaxially with silicon. Outside the core, the planes, at first parallel to the bending contour, continuously bend over the range 15-20°, whilst those at 90° remain aligned with silicon across the interface. Owing to the cylindrical symmetry of those transrotational structures, transmission electron microscopy analyses provided direct evidence of the bending phenomenon and allowed a complete description of the fully relaxed domain structure. A non-conventional mechanism of strain relaxation has been proposed, which is competitive with respect to the usual formation of misfit dislocations. The competitive phenomenon consists of Ni₂Si lattice bending and rearrangement of the interface to minimize the Gibbs free energy of the domain.