Atomic transport in metal/ceramic interfaces under heavy ion irradiation

Abstract

Ion beam mixing is a useful tool to modify the physical properties of interfaces in different materials. Metal/metal systems were extensively studied in the last decade. In the last few years research has been focused on the technologically more important metal/ceramic systems. In these systems, however, there is only limited knowledge on stability and diffusion processes under heavy ion irradiation. In order to collect more information about physical processes, which could be important for applications and in tailoring of interfaces, systematic ion beam mixing experiments on several bi-layer samples have been performed. Different oxide-ceramic substrates (MgO, Al 2O 3, SiO 2, ZrO 2) were covered by thin metallic films (Fe, Cu, Ni, Au, Ag) using a MBE set-up. Ion beam mixing experiments were performed at three different energies (150 keV, 4 and 12 MeV) with Ar-, Kr-and Xe-ions at different temperatures (77–673 K). Mixing behaviour was studied mainly by RBS measurements after the irradiation. The structure and topography of the films prior to and after irradiation were investigated by high resolution scanning electron microscopy (HRSEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). It was of special interest to determine the enhancement of the mixing rate compared to the ballistic mixing. This enhancement can be explained by thermal spikes (temperature independent effect) or by mobile defects produced by the heavy ions during irradiation and/or by chemical driving forces (temperature dependent effects).