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Density Reduction: A Mechanism For Amortization at High IonDoses

Published online by Cambridge University Press:  15 February 2011

E. D. Specht ,
D. A. Walko  and
S. J. Zinkle
E. D. Specht
Affiliation:
Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831–6118
D. A. Walko
Affiliation:
Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831–6118
S. J. Zinkle
Affiliation:
Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831–6118
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Abstract

At cryogenic temperatures, the accumulation of vacancy-interstitial pairs in Al2O3 from atomic displacements associated with ionimplantation produces amorphization. At room temperature, these pairsrecombine, and amorphization occurs only at high doses. X-ray reflectivitymeasurements show that amorphization of the surface of Al2O3 implanted at room temperature with 160 keV Cr+ ions is preceded by a progressive reduction innear-surface density. Monte Carlo simulations show that this densityreduction can be accounted for by high-energy-transfer collisions whichknock atoms deep into the target, leaving widely separated vacancies andinterstitials, which do not recombine. Electron Microscopy shows that atleast some of these vacancies condense into voids. We propose that thisreduction in near-surface density can lead to amorphization at high doses.We present simple approximations for the density reduction expected fordifferent ions and targets.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 321: Symposium E – Crystallization and Related Phenomena in Amorphous Materials—Ceramics, Metals, Polymers, and Semiconductors , 1993 , 399
Copyright
Copyright © Materials Research Society 1994

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References

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