Microstructural changes of Ni induced by Ag+ and Bi+ ion bombardment

Thin (25-60 nm) Ni films are implanted with 40-130 keV Ag+ and 100-200 keV Bi+ and investigated using RBS and TEM. In fine-grain thin films the implantation induces significant recrystallization and grain growth for dose φ ≥ 1015 cm-2. The average grain diameter increases with dose and the growth rate is linearly proportional to the energy deposited into elastic collision, E·v(E), and also depends on film thickness. For high φ, the Ni films exhibit <110> preferred orientation and, a typical plate fibre texture is identified. Ni films evaporated on 673 K substrates show a great number of extended defects without forming microtwins, which are typical in bombarded fine grain films. The high density of defects and the high strain energy produced by ion bombardment along with the tendency to reduce the surface energy at enormous area of grain boundaries and free surface are considered to be the driving forces. Ni atoms activated by energy spikes accomplish short-range movement during relaxation, resulting in the recrystallization and grain growth