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Higher compressive strengths and the Bauschinger effect in conformally passivated copper nanopillars

Jennings, A. T. and Gross, C. and Greer, F. and Aitken, Z. H. and Lee, S.-W. and Weinberger, C. R. and Greer, J. R. (2012) Higher compressive strengths and the Bauschinger effect in conformally passivated copper nanopillars. Acta Materialia, 60 (8). pp. 3444-3455. ISSN 1359-6454.

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Our current understanding of size-dependent strength in nano- and microscale crystals is centered around the idea that the overall strength is determined by the stress required to propagate dislocation sources. The nature and type of these dislocation sources is the subject of extensive debate, however, one commonality amongst these theories is that the ability of the free surface to absorb dislocations is a necessary condition for transition to a source controlled regime. In this work we demonstrate that atomic layer deposition (ALD) of conformal 5–25 nm thick TiO_2/Al_(2)O_3 coatings onto electroplated single crystalline copper pillars with diameters ranging from 75 nm to 1 μm generally inhibits the ability of a dislocation to vanish at the free surface. Uniaxial compression tests reveal increased strength and hardening relative to uncoated pillars at equivalent diameters, as well as a notable recovery of plastic strain during unloading, i.e. the Bauschinger effect. Unlike previous reports, these coated pillars retained the stochastic signature in their stress–strain curves. We explain these observations within the framework of a size-dependent strength theory based on a single arm source model, dislocation theory, and microstructural analysis by transmission electron microscopy.

Item Type:Article
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Greer, J. R.0000-0002-9675-1508
Additional Information:© 2012 Acta Materialia Inc. Published by Elsevier Ltd. Received 26 January 2012. Revised 5 March 2012. Accepted 6 March 2012. Available online 6 April 2012. A.T.J., Z.H.A., and J.R.G. gratefully acknowledge the financial support of the National Science Foundation through a NSF Graduate Research Fellowship to A.T.J. and JRG’s a Career Grant (DMR-0748267) to J.R.G. The experiments were partly performed at the Kavli Nanoscience Institute (KNI). S.W.L. acknowledges the KNI for fellowship support. This research was supported in part by an appointment to the Sandia National Laboratories Truman Fellowship in National Security Science and Engineering, sponsored by Sandia Corp. (a wholly owned subsidiary of Lockheed Martin Corp.) as Operator of Sandia National Laboratories under US Department of Energy Contract No. DE-AC04-94AL85000. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
Group:Kavli Nanoscience Institute
Funding AgencyGrant Number
NSF Graduate Research FellowshipUNSPECIFIED
Kavli Nanoscience InstituteUNSPECIFIED
Department of Energy (DOE)DE-AC04-94AL85000
Subject Keywords:Dislocation boundaries; Copper; Compression test; Nanostructure
Issue or Number:8
Record Number:CaltechAUTHORS:20120613-103523754
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Official Citation:A.T. Jennings, C. Gross, F. Greer, Z.H. Aitken, S.-W. Lee, C.R. Weinberger, J.R. Greer, Higher compressive strengths and the Bauschinger effect in conformally passivated copper nanopillars, Acta Materialia, Volume 60, Issue 8, May 2012, Pages 3444-3455, ISSN 1359-6454, 10.1016/j.actamat.2012.03.013.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:31890
Deposited By: Jason Perez
Deposited On:13 Jun 2012 20:14
Last Modified:09 Oct 2019 21:02

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