This article reports some new details of the Yb silicide formation mechanism. The combination of high-resolution transmission electron microscopy and energy dispersive spectroscopy helped us to unravel several interesting aspects of the silicidation process at the early stage. Interdiffusion between Si and Yb was extensive even at low temperatures (<250 degrees C) and led to the formation of an amorphous layer, followed by the nucleation of crystalline YbSi2-x at the bottom of the amorphous layer. Upon annealing at 350 degrees C, the silicide layer grew thicker as a flat layer of a uniform thickness with two epitaxial relations with the underlying Si lattice. Annealing at higher temperatures (400 degrees C and 500 degrees C) prompted silicide grains with random orientations to nucleate and grow on the epitaxial layer, producing a bilayer morphology. Copyright (C) 2012 John Wiley & Sons, Ltd.