Improvement in crystal quality of epitaxial Ag and Cu films induced by self-ion irradiation

Epitaxial Ag and Cu films ∼ 300 nm thick on Si substrates were irradiated with self-ions (Ag⁺ and Cu⁺) at room temperature to improve crystal quality of the films. The minimum yield of Ag/Si(100) for [100] axial channeling, for example, was reduced from 39% of that for the un-irradiated sample to 13% after irradiation with 300 keV Ag ions to a fluence of 3 × 10¹⁵ ions cm^{- 2}. The self-ion irradiation uniformly improves the crystal quality of the irradiated layer up to a depth of ∼ 200 nm, rather close to the depth corresponding to the end of range of ions, in spite of the non-uniform depth distribution of displaced Ag atoms. In channeling analysis, the energy dependences of dechanneling factors show that dominant defects present in the irradiated films are not dislocations, but twins, stacking faults and/or voids. AFM observations evidence grain growth in a lateral direction at the surface.