High Energy Ion Beam Mixing in Al 2 O 3
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HIGH ENERGY ION BEAM MIXING IN A1 2 03* M. B. LEWIS AND C. J. McHARGUE Metals and Ceramics Division Oak Ridge National Laboratory Oak Ridge, TN 37831 (USA)
ABSTRACT The ion beam mixing technique has been employed to mix metal atoms into the surface layers of A1 2 0 3 . Ion beams of Fe+ and Zr+ in the 1 to 4 MeV energy range were used to irradiate AI 2 0 3 specimens on the surfaces of which films of Some specimens chromium or zirconium had been evaporated. were irradiated at elevated temperatures of 873 or 1173 K. Rutherford backscattering (RBS) and channeling methods were used to measure the metal atom depth profiles near the surface. Analyses of the backscattering data included binary collision calculations using the codes TRIM and MARLOWE. The significance and limitations of high energy (>1 MeV) Evibeams for ion beam mixing experiments is discussed. dence was found for radiation enhanced diffusion and/or solubility of zirconium and chromium in A1 2 0 3 at 873 K. INTRODUCTION In most ion beam mixing (IBM) experiments, the primary ions are produced by ion implantation accelerators with an energy of about 200 keV [1]. These ions are usually much different atomically (e.g., inert gas ions) than the secondaries or target atoms. Although the mean range of the primaries is usually beyond the interfacial planes of interest, multiple scattering of the primary ions can lead to a fraction of them being implanted at short range near those planes thereby affecting the outcome of the IBM experiment. For example, in the case of 200 key Ar+ on A12 0 3 , multiple scattering calculations, discussed below, give a near-surface (4200 A) argon density that is However, it is known that gaseous about 4% of the peak density at 1000 A. impurities of only about 100 parts per million in metals can have a dramatic effect on the nucleation of radiation-induced cavities [2] as well as other These facts have caused us to investithermal and mechanical properties. gate both the use of more energetic (>1 MeV) primary ions and the use of non-gaseous or metallic ions (Fe+, Zr+). This work is a continuation of measurements of the changes in properties of Al 2 03 due to ion beam irradiation [3-61. Previous measurements [3] of 1 MeV Fe+ ion beam mixed chromium and zirconium films on A1 2 0 3 showed that most of the film mixed atoms occupied substitutional sites and that surface disorder in A12 0 3 appeared minimal even for a beam fluence of 2 x 2 1017 Fe+/cm . This is believed to be the result of (a) minimal deposition of the ion beam atoms near the region of metal-substrate interface and (b) the self annealing ionization accompanying the high energy primary ion beam. In this work we have extended the results reported in ref. 3 by continuing to investigate ion beam mixing of metallic films evaporated on *Research sponsored by the Division of Materials Sciences, U.S. Department of Energy, under contract W-7405-eng-26 with Union Carbide Corporation. Mat. Res.
Soc.
Symp. Proc.
Vol.
27
(1984)
Published by Elsevier Science Publishing Co.,
Inc.
772
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