Plasma synthesis of hexagonal-pyramidal graphite hillocks.

Abstract: 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 800nm across and up to 1μm 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. [Copyright &y& Elsevier]