MOLECULAR-DYNAMICS STUDY OF SPUTTERING OF CU(111) UNDER AR ION-BOMBARDMENT

We have used the molecular dynamics (MD) technique using many-body interaction potentials to analyse in detail the processes leading to sputter emission, in order to gain a microscopic understanding of low energy bombardment phenomena Calculations were performed for a Cu (111) single crystal surface bombarded with Ar atoms in the energy range from 10-1000 eV. The results presented for low bombarding energies are mainly concerned with the near sputtering threshold behaviour, yields and depth of origin of sputtered atoms. Furthermore, it is found, that in addition to sputtered atoms, a large number of ad-atoms at the surface are generated during the evolution of the collision cascade. At higher energies the question of cluster emission and especially their energy distribution and angular distribution are addressed. It was found that the energy distributions for the dimers and monomer atoms exhibit a similar dependence on emission energy as has been observed recently also experimentally. For atoms good agreement with the theoretical Sigmund-Thompson energy distribution was observed. However, for dimers we found that the energy distributions exhibit an asymptotic behaviour at high energies with E(-3) rather than with E(-5), as predicted in previous modelling of cluster emission. Concerning the angular distributions six emission spots, three strong ones in the [110] and three weak ones in the [100] direction were found for atoms, but for dimers only emission spots in the [110] direction were observed, in agreement with experimental results.