Ion beam mixing, diffusion, and phase stability in Cu/Al 2 O 3 interfaces
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Ion beam mixing, diffusion, and phase stability in CuyAl2 O3 interfaces K. Neubeck, H. Hahn, and A. G. Balogh Department of Materials Science, Technical University, Darmstadt, Germany
H. Baumann and K. Bethge Institut f¨ur Kernphysik, J. W. Goethe Universit¨at, Frankfurt am Main, Germany
D. M. R¨uck and N. Angert Institute for Heavy Ion Research (GSI), Darmstadt, Germany (Received 5 October 1994; accepted 1 August 1995)
Ion beam mixing, diffusion properties, and phase stability have been investigated in CuyAl2 O3 bilayer samples. Specimens were prepared by vapor deposition and irradiated with 150 keV Ar1 ions up to a fluence of 1.5 ? 1017 Ar1ycm2 . Sample temperature under irradiation was varied between 77 K and 673 K. The mixing behavior was studied by analyzing the concentration depth profiles, determined by Rutherford Backscattering Spectroscopy. It was found that mixing efficiencies of Cu, Al, and O scale with Ar1 fluence. Radiation enhanced diffusion (RED), observed above room temperature, is separated from ballistic mixing and high temperature diffusion. The migration enthalpy for interdiffusion in the RED region (between RT and 300 ±C) was estimated to be approximately 0.3 eV. Sputtering yields depending on temperature gradient near to sample and phase stability versus ion dose and temperature are also discussed.
I. INTRODUCTION
The understanding of structure, stability, and modification of metal/ceramic interfaces is of upmost importance for many technological applications, such as coating of metallic alloys, development of multilayer systems, improvement of adhesion in microelectronic devices, etc. A further field of interest is the development of new structural materials for high power fusion devices with special properties combining high strength, high electrical conductivity, and low swelling rates. These materials have to be stable under high thermal load and long term neutron irradiation. Dispersion strengthened Cu–Al2 O3 alloys, for example, commercial CuAl25, an alloy with 0.25 at. % Al2 O3 in Cu matrix are among the best candidates for this purpose.1 Transmission electron microscopy on CuAl25 samples, irradiated with 300 keV Cu1 ions, shows a significant change in the size distribution of Al2 O3 particles after irradiation,2 emphasizing the necessity of detailed studies of mixing behavior of alumina/copper interfaces. For the new fusion reactors, an operation period of several years without maintenance is expected. During this time, damage fluences on the order of 100 dpa (displacements per atom) could be achieved. It is straightforward to simulate the neutron damage by irradiating CuyAl2O3 bilayer samples with heavy ions for a few hours. Because of the very low J. Mater. Res., Vol. 11, No. 5, May 1996
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displacement rates (about 1026 dpays) of neutron test facilities, the same damage deposition would require irradiation times of several years.3 The goal of the present work is to investigate the
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