Solute redistribution during high dose, high temperature implantations of 60keVCu+ions into polycrystalline titanium

Abstract

The correspondence between observed and expected impurity distributions occurring in high dose, high temperature ion implantation, has been investigated for 60 keV Cu+ ions in poly-crystalline Ti. The expected atomic profiles are caclulated assuming a simple sputtering model of retention, and the actual profiles were determined by ion backscattering analysis. Implantation carried out at elevated temperatures (∼500–600°C) and to high doses (≳ 5.0 1016 ions/cm2) resulted in a marked redistribution of stopped material, with the Cu accumulating to form a peak well beyond the region of energy deposition. The magnitude and position of this deeper peak were found to be strongly dependent on the incident dose and target temperature, but only weakly dependent on dose rate and irradiation time. Further, in the early stages of its development (l∼2.0 1017 ions/cm2, 500°C) this anomalous peak propagated into the bulk without any significant broadening and by a mechanism which caused its position to depend linearly on the incident dose. The formation and subsequent migration of a solute-defect complex down its own defect concentration gradient is proposed as the most probable mechanism responsible for the observed redistribution.