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Now showing items 1 - 3 of 3

  • Angular and velocity distributions of tungsten sputtered by low energy argon ions

    E. Marenkov   K. Nordlund   I. Sorokin   A. Eksaeva   K. Gutorov   J. Jussila   F. Granberg   D. Borodin  

    Abstract Sputtering by ions with low near-threshold energies is investigated. Experiments and simulations are conducted for tungsten sputtering by low-energy, 85–200 eV Ar atoms. The angular distributions of sputtered particles are measured. A new method for molecular dynamics simulation of sputtering taking into account random crystallographic surface orientation is developed, and applied for the case under consideration. The simulations approximate experimental results well. At low energies the distributions acquire “butterfly-like” shape with lower sputtering yields for close to normal angles comparing to the cosine distribution. The energy distributions of sputtered particles were simulated. The Thompson distribution remains valid down to near-threshold 85 eV case. Highlights • Angular and energy distributions of sputtered particles are considered for low-energy sputtering. • A new algorithm for molecular dynamics simulations of polycrystalline target is proposed. • Results of the simulations agree with experimental findings both obtained by us and found in literature.
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  • Effects of the short-range repulsive potential on cascade damage in iron

    J. Byggmästar   F. Granberg   K. Nordlund  

    Abstract Recent work has shown that the repulsive part of the interatomic potential at intermediate atomic separations strongly affects the extent and morphology of the damage produced by collision cascades in molecular dynamics simulations. Here, we modify an existing embedded atom method interatomic potential for iron to more accurately reproduce the threshold displacement energy surface as well as the many-body repulsion at intermediate and short interatomic distances. Using the modified potential, we explore the effects of an improved repulsive potential on the primary damage production and the cumulative damage accumulation in iron. We find that the extent of the damage produced by single cascades, in terms of surviving Frenkel pairs, directly correlates with the change in threshold displacement energies. On the other hand, the damage evolution at higher doses is more dependent on the formation and stability of different defect clusters, defined by the near-equilibrium part of the interatomic potential.
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  • Effect of random surface orientation on W sputtering yields

    J. Jussila   F. Granberg   K. Nordlund  

    Highlights • The effect of random surface orientations on the sputtering yields was studied. • Low index surfaces and random orientations of the surface was investigated. • The sputtering yield depended heavily on the surface orientation. Abstract In this study, we investigate the sputtering yield of tungsten surfaces by energetic particles, focusing on the effect of surface orientation and the incoming irradiation angle, by means of molecular dynamics. We develop a simulation approach to simulate sputtering from completely random surface orientations. This allows obtaining the sputtering yields averaged over a sufficiently large number of orientations, to obtain statistically significant yields representative of a polycrystalline sample with random grain orientations. We find that the total sputtering yield is dependent on the surface orientation, and that the results for random surfaces are clearly different from that of any of the low-index ones or their average. The different low index surfaces and the random surfaces also showed that the sputtering yield is dependent on the incoming angle of the ion. The outgoing angle of the sputtered tungsten atoms was observed to be very sensitive to the surface orientation. Different features on the tungsten surface were observed to drastically affect the sputtering yield at certain angles.
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