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Length-scale-based hardening model for ultra-small volumes

Published online by Cambridge University Press:  01 October 2004

J.M. Jungk ,
W.M. Mook ,
M.J. Cordill ,
M.D. Chambers ,
W.W. Gerberich ,
D.F. Bahr ,
N.R. Moody  and
J.W. Hoehn
J.M. Jungk*
Affiliation:
Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455
W.M. Mook
Affiliation:
Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455
M.J. Cordill
Affiliation:
Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455
M.D. Chambers
Affiliation:
Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455
W.W. Gerberich
Affiliation:
Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455
D.F. Bahr
Affiliation:
Department of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164
N.R. Moody
Affiliation:
Microsystems and Materials Mechanics, Sandia National Laboratories, Livermore, California, 94550
J.W. Hoehn
Affiliation:
Seagate Technology LLC, Minneapolis, Minnesota 55435
*
a) Address all correspondence to this author. e-mail: jungk@cems.umn.edu
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Abstract

Understanding the hardening response of small volumes is necessary to completely explain the mechanical properties of thin films and nanostructures. This experimental study deals with the deformation and hardening response in gold and copper films ranging in thickness from 10 to 400 nm and silicon nanoparticles with particle diameters less than 100 nm. For very thin films of both gold and copper, it was found that hardness initially decreases from about 2.5 to 1.5 GPa with increasing penetration depth. Thereafter, an increase occurs with depths beyond about 5–10% of the film thickness. It is proposed that the observed minima are produced by two competing mechanisms. It is shown that for relatively deep penetrations, a dislocation back stress argument reasonably explains the material hardening behavior unrelated to any substrate composite effect. Then, for shallow contacts, a volume-to-surface length scale argument relating to an indentation size effect is hypothesized. A simple model based on the superposition of these two mechanisms provides a reasonable fit to the experimental nanoindentation data.

Keywords

Thin filmHardness
Type
Articles
Information
Journal of Materials Research , Volume 19 , Issue 10 , October 2004 , pp. 2812 - 2821
Copyright
Copyright © Materials Research Society 2004

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References

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