Molecular dynamics simulations of the bombardment of iron by chromium ions.

This thesis presents the results of an investigation of Cr keV bombardment of a crystalline Fe surface by molecular dynamics simulations. Different parameters of the bombardment were considered in particular those that pertain to surface pretreatment prior to PVD hard coatings.Molecular dynamics simulations of 200 eV to 5 keV Cr bombardment of a-Fe at normal incidence have been performed at crystal temperatures of 0 K, 300 K and 700 K using many body potentials which were modified to properly represent the energetic interaction range. The sputtering yield increases with energy showing an enhancement at crystal temperature 700 K, the same as for adatom formation. Defect production, such as vacancies and interstitials, increase in general with energy, and their distribution profiles change with the crystal temperature.The directional effect on the bombardment of Fe(100) surface at temperature 700 K, with 2.4 keV Cr shows a factor of two enhancement in the sputtering yield at low oblique angles with the initiation of reflection of Cr ions at high oblique incidence. Bombardment with noble gas ions has shown to be efficient and to produce a positive mass effect on sputtering compared to using a metal ion. Non linear enhancement of the total and cluster sputtering yield has been observed under diatomic Cr[2] projectile bombardment of Fe at 2.4 keV and 4.8 keV per dimer. The depth of origin of the sputtered particles seems to be insensitive to the bombardment parameters, but the sputtering rate of the surface does depend on the incidence parameters. The increase of sputtering yield at different bombardment conditions is the result of high yield events.