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Journal of Nanomaterials
Volume 2009, Article ID 204281, 8 pages
http://dx.doi.org/10.1155/2009/204281
Research Article

Strength and Fracture Resistance of Amorphous Diamond-Like Carbon Films for MEMS

1Mechanical Engineering, Johns Hopkins University, Baltimore, MD 21218, USA
2Aerospace Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA

Received 6 December 2008; Accepted 22 May 2009

Academic Editor: Rakesh Joshi

Copyright © 2009 K. N. Jonnalagadda and I. Chasiotis. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The mechanical strength and mixed mode I/II fracture toughness of hydrogen-free tetrahedral amorphous diamond-like carbon (ta-C) films, grown by pulsed laser deposition, are discussed in connection to material flaws and its microstructure. The failure properties of ta-C were obtained from films with thicknesses 0.5–3 m and specimen widths 10–20 m. The smallest test samples with 10 m gage section averaged a strength of 7.3 1.2 GPa, while the strength of 20-m specimens with thicknesses 0.5–3 m varied between 2.2–5.7 GPa. The scaling of the mechanical strength with specimen thickness and dimensions was owed to deposition-induced surface flaws, and, only in the smallest specimens, RIE patterning generated specimen sidewall flaws. The mode I fracture toughness of ta-C films is , while the results from mixed mode I/II fracture experiments with cracks arbitrarily oriented in the plane of the film compared very well with theoretical predictions.