Influence of the polar angle of incidence on secondary ion formation in self‐sputtering of silver

The influence of the projectile impact angle on secondary ion formation was studied using a computer simulation model applied to the bombardment of an amorphous silver crystal by 5-keV Ag atoms. The model employs a molecular dynamics (MD) scheme for the description of particle dynamics within the atomic collision cascade. The electronic degree of freedom is treated within the framework of a free electron gas model incorporating kinetic excitation by electronic friction and electron promotion. Transport of the excitation energy away from the spot of generation is treated by a diffusive approach. In combination with a rate equation model for electronic charge transfer an individual ionization probability a + is assigned to each sputtered particle. The results reveal that the average ionization probability of sputtered atoms increases upon the transition from normal to oblique incidence. The dependence of α + on the emission velocity of ejected atoms is traced back to the temporal structure of the excitation profile induced after projectile impact.