Plasma synthesis of hexagonal-pyramidal graphite hillocks

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We report on the synthesis and natural occurrence of hexagonal-pyramidal graphite hillocks on graphite crystal substrates. Synthetic hillocks were obtained from flexible graphite sheets and highly oriented pyrolytic graphite via argon plasma etching in a standard helicon configuration reactor. High-resolution transmission electron microscopy and electron diffraction suggest these hillocks have a high degree of perfection. Their size distribution ranges from 50 to 800 nm across and up to 1 μm along the c-axis. As a reference, natural crystals from Tanzania exhibiting the same morphology are presented. Also, a formation mechanism of the plasma-synthesized structures by an etching process is detailed. This new type of vertically aligned carbon nano- and microstructures presents a peculiar geometry including nano-arches at the graphite edge planes which induce a strong resistance to the plasma etching.

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© 2014 Elsevier Ltd. All rights reserved. Publisher's version of record: http://dx.doi.org/10.1016/j.carbon.2014.04.084

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