Diffusion processes in metal/ceramic interfaces under heavy ion irradiation

Abstract

Ion beam techniques are frequently used to modify the physical properties of interfaces. Ion beam mixing and radiation enhanced diffusion (RED) of several metal–ceramic interfaces were investigated. Polished Al 2O 3, SiO 2 and MgO crystals were chosen as substrates. Thin metal films of Fe, Ni and Cu, with a thickness of 70 nm, were evaporated onto these substrates using Molecular Beam Epitaxy (MBE). The bilayer systems were irradiated with 150 keV Ar + ions with a dose of 2 × 10 16 Ar +/cm 2 in a temperature range from 77 to 373 K. Film thickness and ion energy were so chosen as to obtain a maximum nuclear stopping power at the interface, calculated by the computer code TRIM. Rutherford Backscattering Spectrometry (RBS) was used to determine the concentration depth profiles and the diffusion lengths for each of the elements. Different diffusion processes, i.e. ballistic mixing and radiation enhanced diffusion, were separated using the low and medium temperature data. The results are compared with other known systems.