Morphology and changes of elemental surface composition of tungsten bombarded with carbon ions

Surface morphology has a strong influence on sputtering and implantation. A newly developed Monte-Carlo code SDTrimSP-2D simulates ion bombardment of surfaces with a 2D surface morphology (1D is depth and another dimension is lateral) defined by a vertical cross-section of the solid. The simulations allow to study numerically the interdependency of surface geometry and sputtering and implantation processes. Experimental results of the bombardment of W layers deposited on polished pyrolytic graphite with 6 keV C ions were used for comparison with results of the simulation. Free parameters of the code, particularly the so-called anisotropy coefficient, are calibrated by comparison of the macroscopic evolution of the elemental surface composition to the experimental results. After calibration, the code reproduces qualitatively the evolution of the shape of nano-scale surface structures observed by atomic force microscopy and by scanning electron microscopy. The histograms of the surface heights obtained by measurements and by the simulation show qualitative agreement. Local values of the W sputtering yield and C areal density, which are accessible only from the simulations, have been found to be strongly dependent on the nano-scale geometry