Range study of Eu implanted into Si channeling directions : evidence for the Z/sub 1/ effect

Abstract

Eu ions have been implanted along the Si ‹100›, ‹111›, and ‹110› directions at 623 K with energies ranging from 15 keV to 50 keV. The depth profiles have been measured using Rutherford backscattering spectroscopy (RBS). A signature of the nuclear Z₁ effect, namely, the enhanced ion range found for some projectiles penetrating into amorphous Si, has been observed under channeling conditions for the Eu ions, through the appearance of extended long tails. The results have been compared to MARLOWE calculations using different interatomic potentials in order to simulate the mechanism responsible for the Z₁ effect. In addition, ab initio calculations for the Eu-Si interatomic potential have been performed in order to investigate the origin of the nuclear Z₁ effect. These calculations show that the formation of quasimolecules at very low energies is responsible for the enhanced ion range.