Surface stress-induced island shape transition in Si(001) homoepitaxy

A low-energy electron microscopy study of two-dimensional Si(001) island shapes near thermal equilibrium on 10×15 μm² large single-domain terraces reveals a continuous increase of island aspect ratio and a shape transition from elliptical to “American-football”-like with increasing island size. The size-dependent island shapes are driven by elastic relaxation caused by the intrinsic surface stress anisotropy present on Si(001). Analysis of the measured elliptical island shapes based on an elastic-model calculation allows a quantitative determination of step energies and of the surface stress anisotropy as a function of temperature.