Materials Science

Plated Pillars

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Science  18 Dec 2009:
Vol. 326, Issue 5960, pp. 1591
DOI: 10.1126/science.326.5960.1591-c
CREDIT: BUREK AND GREER, NANO LETT. 10.1021/NL902872W (2009)

Mechanical testing of submicrometer-sized metal pillars has shown significant strengthening on decreasing the pillar dimensions. Analysis of such experiments is complicated, however, because the traditional focused ion beam method for making the pillars causes damage through the implantation of Ga+ ions and leads to vertical tapering. Burek and Greer turned to lithographic techniques, using an electron beam to pattern a poly(methylmethacrylate) (PMMA) film. The patterned film was in turn used to template pillar growth by deposition of gold or copper through electroplating. The plating conditions could be tuned to vary the microstructure of the pillars, which ranged from single crystals to twin domain and highly nanocrystalline structures. Pillars for compressive testing were fabricated by halting plating before reaching the top of the PMMA layer; for tensile testing, the pillars were overplated with a cap to facilitate gripping of the sample. The pillars showed little tapering and exhibited diameters as small as 25 nm, much smaller than the lower limit attainable by a focused ion beam.

Nano Lett. 10.1021/nl902872w (2009).

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