Workshops > Non-equilibrium Interface and Surface Dynamics

Non-equilibrium Interface and Surface Dynamics

Dynamics of Strained Pyramids

Thomas Frisch

Université Paul Cézanne, CNRS


We consider the growth of an elastically strained thin semiconductor film in epitaxial conditions We investigate the dynamical evolution of the morphological (Asaro-Tiller-Grinfel'd) instability of a strained silicon-germanium film driven by surface diffusion during growth and annealing, in the presence of surface energy anisotropy. We discuss the effect of the anisotropy and its consequence on the coarsening dynamics of the film. Based on experimental properties, we construct an ad-hoc gamma-plot of the surface energy devised for the silicon-germanium system which takes into account the presence of the (105) regularized facets. A small anisotropy induces a complete change in the coarsening dynamic. The non-interrupted coarsening (Ostwald ripening) at stake for isotropic strained films [1,2] is destroyed by anisotropy and the system is glued in metastable states [3]. We show numerically, using a small slope approximation and a nonlinear expansion that the formation of pyramids leads to a dense array of quantum dots whose density and height are function of the deposited volume. We characterize the statistical properties of the resulting pyramids and show that both their density and mean volume increase with the total amount of matter deposited.

We will then present a phenomenological model which shows that coarsening is interrupted due to the interplay between elastic deformations, wetting effects and the surface energy anisotropy. Our results will be illustrated and compared to some annealing and growth, experimental results on silicon-germanium systems grown by MBE.

Joint work with Jean-Noel Aqua, Adrien Gouye, Antoine Ronda, Isabelle Berbezier (Affiliation Lab: IM2NP, Aix-Marseille University)

[1] J.-N. Aqua, T. Frisch and A. Verga, Phys. Rev B. 76, 165319, (2007)
[2] J.-N. Aqua, T. frisch and A. Verga, Phys. Rev E, 81, 021605, (2010)
[3] J.-N. Aqua and T. Frisch , Phys. Rev. B, In Press (2010)