Localized compression and shear tests on nanotargets with a Berkovich tip and a novel multifunctional tip
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Peralta, C. Friesen, and N. Chawla Fulton School of Engineering, Arizona State University, Tempe, Arizona 85287
E. Traversa University of Rome “Tor Vergata”, NAST, Via della Ricerca Scientifica, Roma 00133, Italy
K. Sieradzki Fulton School of Engineering, Arizona State University, Tempe, Arizona 85287 (Received 29 July 2008; accepted 1 October 2008)
This article presents an experimental procedure to perform highly localized compression tests on nanoscale structures/features, such as nanospheres and nanopillars, via standard nanoindentation equipment. Current manufacturing capabilities, such as focused ion beam (FIB), lend themselves well to the creation of micron-spaced nanostructures, but it is fundamental to target an individual instance with little or no damage to the surrounding ones. The procedure successfully addresses the problem of locating and testing purposely designed nanostructures of order of 50 nm or less. The technique is illustrated for the case of closely spaced arrays of nanopillars, which were successfully manufactured, characterized, and tested through several pieces of equipment. For the purposes of compression, along with a traditional Berkovich tip, a new multifunctional (MF) tip was devised. This last tip is endowed with a complex contact geometry enabling both atomic force microscope (AFM) scanning and flat punch compression of the nanostructure. The levels of accuracy in tip positioning as well as robustness to alignment errors are unprecedented in comparison with previous in situ compression tests. As a consequence, the MF tip becomes a versatile tool that can be used beyond uniform compression. As an example, ancillary shear tests in controlled conditions are reported. Such results may lay the bases for metal-forming processes at the nanoscale, such as nanoforging or cutting operations, which are relevant to MEMS design and manufacturing. I. INTRODUCTION
Nowadays, nanoindentation is perhaps the prime technique used to investigate and characterize the mechanical properties of the materials on the nanoscale. It has long been used to study the elastic, plastic, and fracture properties on the surfaces of bulk samples, as well as for thinfilms.1–3 More recently, it became possible to perform controlled compression and bending tests on nanostructures smaller than a micron, such as nanospheres,4–7 nanowires,8–10 and nanopillars.11–25 Some of the referenced authors devised experimental setups to perform pioneering compression tests by customizing standard equipment to this purpose. In general, the nanoindenter that is appropriate for this type of exploration is a machine that embeds two functionalities. On one side it a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2009.0099
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http://journals.cambridge.org
J. Mater. Res., Vol. 24, No. 3, Mar 2009 Downloaded: 22 Mar 2015
can be used for scanning-probe microscopy similarly to an atomic force microscope (AFM) in contact mode, where the probe is replaced by a sharp and hard diamond tip. On
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