Atomistic Description of Ion-Induced Surface Patterning - Role of Surface / Bulk Defects and Viscous Flow

The role of viscous flow of amorphous Si, Ge, and SiO2 for surface pattern formation under ion irradiation is still a matter of discussions. Strong indications for viscous flow exist for ion energies >10keV. A theoretical treatment of ion-induced surface patterning including viscous flow is extremely difficult because mechanisms of surface patterning like curvature dependent ion erosion and diffusion cannot be separated. Therefore, a program package has been developed which allows a simultaneous treatment of the collision cascades, thermally activated processes and viscous flow. The 3D atom relocation by the collision cascades are calculated in the Binary Collision Approximation, the thermally activated relaxation of energetic atomic configurations as well as diffusive processes are simulated be a very efficient bit-coded kinetic 3D Monte Carlo algorithm, and the viscous flow is taken into account by a crude model allowing distant annihilation of interstitials at the surface. The simulations prove a significant contribution of viscous flow to surface patterning. A comparison of simulated pattern with experimental results will be presented.