Orientation dependence of the elastic instability on strained SiGe films

TL;DR

This study investigates how the orientation of SiGe films influences the development of elastic instability, revealing that surface orientation significantly affects the onset and evolution of morphological changes during annealing.

Contribution

The paper provides experimental evidence and a continuum model explaining the orientation-dependent development of elastic instability in strained SiGe films.

Findings

Instability develops on Si(001) but not on Si(111) surfaces.

Surface stiffness strongly influences the onset of instability.

Elasticity and surface energy anisotropy retard the instability on Si(111).

Abstract

At low strain, SiGe films on Si substrates undergo a continuous nucleationless morphological evolution known as the Asaro-Tiller-Grinfeld instability. We demonstrate experimentally that this instability develops on Si(001) but not on Si(111) even after long annealing. Using a continuum description of this instability, we determine the origin of this difference. When modeling surface diffusion in presence of wetting, elasticity and surface energy anisotropy, we find a retardation of the instability on Si(111) due to a strong dependence of the instability onset as function of the surface stiffness. This retardation is at the origin of the inhibition of the instability on experimental time scales even after long annealing.