Measuring the elastic modulus and residual stress of freestanding thin films using nanoindentation techniques

A new method is proposed to determine the elastic modulus and residual stress of freestanding thin films based on nanoindentation techniques. The experimentally measured stiffness-displacement response is applied to a simple membrane model that assumes the film deformation is dominated by stretching...

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Bibliographic Details
Published in:Journal of materials research 2009-09, Vol.24 (9), p.2974-2985
Main Authors: Herbert, Erik G., Oliver, Warren C., de Boer, Maarten P., Pharr, George M.
Format: Article
Language:English
Subjects:
Applied and Technical Physics
BENDING
Biomaterials
DEFORMATION
Elastic properties
ELECTROSTATICS
Inorganic Chemistry
Materials Engineering
MATERIALS SCIENCE
MECHANICAL PROPERTIES
MEMBRANES
Microelectromechanical systems (MEMS)
Nanotechnology
THERMAL EXPANSION
Thin film
THIN FILMS
VERIFICATION
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Summary:A new method is proposed to determine the elastic modulus and residual stress of freestanding thin films based on nanoindentation techniques. The experimentally measured stiffness-displacement response is applied to a simple membrane model that assumes the film deformation is dominated by stretching as opposed to bending. Dimensional analysis is used to identify appropriate limitations of the proposed model. Experimental verification of the method is demonstrated for Al/0.5 wt% Cu films nominally 22 µm wide, 0.55 µm thick, and 150, 300, and 500 µm long. The estimated modulus for the four freestanding films match the value measured by electrostatic techniques to within 2%, and the residual stress to within 19.1%. The difference in residual stress can be completely accounted for by thermal expansion and a modest change in temperature of 3 °C. Numerous experimental pitfalls are identified and discussed. Collectively, these data and the technique used to generate them should help future investigators make more accurate and precise measurements of the mechanical properties of freestanding thin films using nanoindentation.
ISSN:0884-2914
2044-5326
DOI:10.1557/jmr.2009.0360