The evolution of Si(100) surfaces has been studied during oblique high-fluence ion sputtering by means of atomic force microscopy. The observed surface morphology is dominated by nanoscale ripples and kinetic roughening at small and large lateral scales, respectively. The large-scale morphology exhibits anisotropic scaling at high fluences with different roughness exponents ${\alpha }_n=0.76\pm 0.04$ and ${\alpha }_p=0.41\pm 0.04$ in the directions normal and parallel to the incident ion beam, respectively. Comparison to the predictions of single field and two-field (“hydrodynamic”) models of ion erosion suggests the relevance of nonlinearities that are not considered in the simpler anisotropic Kuramoto-Sivashinsky equation.

• Received 9 January 2009

DOI:https://doi.org/10.1103/PhysRevB.79.115437