Hardness and modulus of ultrananocrystalline diamond/hydrogenated amorphous carbon composite films prepared by coaxial arc plasma deposition

Kenji Hanada, Tomohiro Yoshida, You Nakagawa, Hiroki Gima, Aki Tominaga, Masaaki Hirakawa, Yoshiaki Agawa, Takeharu Sugiyama, Tsuyoshi Yoshitake

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4 Citations (Scopus)

Abstract

Ultrananocrystalline diamond (UNCD)/hydrogenated amorphous carbon (a-C:H) composite (UNCD/a-C:H) films were deposited in hydrogen atmospheres by coaxial arc plasma deposition, and the effects of hydrogenation on the mechanical properties were studied on the basis of spectroscopic structural evaluations. The existence of UNCD grains in the films was confirmed by transmission electron microscopy and X-ray diffraction. Non-hydrogenated films prepared in no hydrogen atmosphere exhibited a 22 GPa hardness and 222 GPa Young’s modulus, and the sp3/(sp2 + sp3) ratio estimated from the X-ray photoemission spectra was 41 %. For the films prepared in a 53.3-Pa hydrogen atmosphere, whereas the hardness increases to 23 GPa, the modulus decreases to 184 GPa. The UNCD grain size estimated using Scherrer’s equation and the sp3/(sp2 + sp3) ratio were 2.3 nm and 64 %, respectively, both of which are remarkably increased as compared with those of the non-hydrogenated films. From the near-edge X-ray absorption fine structure spectra, it is considered that σ*C–H bonds are alternatively formed instead of π*C=C, which probably results in the enhanced hardness and reduced modulus by hydrogenation. In addition, it was found that the formation of olefinic and aromatic structures remarkably softens the UNCD/a-C:H film.

Original languageEnglish
Pages (from-to)205-210
Number of pages6
JournalApplied Physics A: Materials Science and Processing
Volume119
Issue number1
DOIs
Publication statusPublished - Jan 1 2015

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Materials Science(all)

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