九州シンクロトロン光研究センター
県有ビームライン利用報告書
課 題 番 号 ： 2009085S

Ｂ Ｌ 番 号 ： 12（様式第 4 号）

同軸型アークプラズマ堆積法によりバイアス印加下で堆積された
ナノダイヤモンド膜の化学結合構造
Chemical bonding structures of nanodiamond films deposited under negative biases
by coaxial arc plasma deposition
ア リ モ ハ メ ド .ア リ , イ ス ラ ナ イ ム , シ ュ リ ナ ー ト ヴ ァ ラ ピ ル , 大 植 英 生 ,岩尾 友貴, 吉武 剛
Ali M. Ali, Eslam Naeim, Sreenath Mylo Valappil, Hideki Ohue,
Yuki Iwao, and Tsuyoshi Yoshitake
九州大学大学院総合理工学府量子プロセス理工学専攻

Department of Applied Science for Electronics and Materials, Kyushu University※１※２※３※４

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１．概要（注：結論を含めて下さい）
Nanodiamond composite (NDC) films, wherein diamond nanocrystallites with diameters of lessthan 10 nm are embedded in an amorphous carbon (a -C) matrix, have received much attention
since they possess physical properties similar to those of diamond and relatively smoothsurfaces. They are promising candidates for a variety of applications such as elec tronic
devices, detectors, hard coating, microelectromechanical systems (MEMS), andnanoelectromechanical system (NEMS). NDC films were deposited by coaxial arc plasma
deposition (CAPD) on cemented carbide (WC-Co) substrates with negative bias voltage during
the deposition. The films deposited on a biased substrate achieved an evident enhancement in
the hardness to 60 GPa and Young’s modulus to 635 GPa, as compared with the hardness of 50
GPa and Young’s modulus of 520 GPa of films deposited without negative bias. Thissignificant improvement in the mechanical properties is consistent with enhanced C 1s→ σ*transitions in the films.

636406260630

5962558
57

620

56

Young's modulus (GPa)635
61
Hardness (GPa)

２．背景と目的
Nanodiamondcomposite(NDC),
comprising
nanodiamond grains of less than 10 nm in diameter and an
a-C matrix, is a carbon-based nanomaterial applicable tohard and biomedical coatings, due to high hardnesses, lowfriction coefficients, and high affinities for living bodies.
Nano-composite structures have received much attention,
since enhancements in the hardness, friction and wear
performance are expected due to the nano-composite
structures. At present, the research has meanly focused onthe preparation of nanodiamond films by chemical vapor
deposition (CVD), microwave plasma and hot filament
assisted chemical vapor deposition. But there has beenless research on the effects of negative bias voltage on thedeposition and properties of the nanodiamond films. It is
well known that negative bias application to substrates
enhances their mechanical properties, particularly thehardness and adhesion strength, of DLC films prepared byphysical vapor deposition. This work was primarily aimed
to study the influence of different negative bias frequency
on the growth of NDC films prepared by coaxial arc
plasma deposition (CAPD). The effects on the mechanicaland structural properties of the films were investigated.

61555540102030405060708061090 100

Bias frequency (KHz)
Figure 1 Dependence of hardness and Young’s
modulus on negative bias frequency.

３．実験内容（試料、実験方法、解析方法の説明）
NDC films were deposited on negatively-biased WC-Co
substrates at base pressures of less than 10−4 Pa by CAPD
Figure 2 NEXAFS spectra of NDC films deposited atwith a graphite target. WC–Co substrates (K-type
negative bias frequency of 10 KHz (black), 50 KHz
cemented tungsten carbide) with a dimension(red), and 90 KHz (blue).
of 10 × 4.5 mm were employed for film deposition. Avoltage of 100 V was applied to the arc plasma gun equipped with a 720 µF capacitor. The repetition rate ofdischarges was 1 Hz. The substrate holder was biased at –80 V in pulse with a frequency of 10, 30, 50, 70 and90 kHz. The hardness and Young’s modulus of the films were estimated by nanoindentation with an applied
indentation load of 0.5 mN/10 s. X-ray photoelectron and near-edge X-ray absorption fine structure (NEXAFS)
spectroscopies were employed for characterizing the chemical bonding structures of the films.
４．実験結果と考察
The negative bias frequency dependence of the hardness (black line) and Young’s modulus (blue line) are
shown in Fig. 1. It clearly shows that the hardness and Young’s modulus increases with decreasing bias
frequency. The hardness and Young’s modulus at 10 kHz are 62 GPa and 636 GPa, respectively. The negativebias application increased the hardness by 10 GPa as compared with that of the films deposited under no bias,
which indicates that the negative bias electrically attracts positively-charged carbon species to the substrates.
For a complementary structural analysis, near-edge X-ray absorption fine structure (NEXAFS) spectroscopy
was obtained for the deposed samples (see fig. 2). The spectra exhibit sharp absorption bands from a C 1s→ σ*
and C 1s→ * transitions, which are characteristic of sp2 and sp3hybridized carbon (double bond) and (singlebond), respectively. The relative intensity of σ* peak gradually enhanced compared with the * peak, withdecreasing the negative bias frequency, which agrees with hardness enhancement by decreased bias frequency.
This might imply that the negative bias plays a role in enhancing the formation of nanocrystalline diamond andreducing the internal stress of the films.

５．今後の課題
In this work, the role of negative bias in the enhancement of mechanical properties, and the relationshipbetween the films hardness and C 1s→ σ* and C 1s→ * transitions were investigated. The results
demonstrated that the use of negative bias enhance the formation of sp3 bonds which work on improving themechanical properties of the deposited films.
６．参考文献[1] K. Hanada et al. Appl. Phys. A, 119:205–210, (2015).
[2] Y.S. Li, A. Hirose, J. Appl. Phys. 101, 073503 (2007).
[3] A. M. Ali et al. Appl. Phys. Express 13, 065506 (2020).
[4] Mohamed Egiza et al. Coatings, 8, 359 (2018).
[5] A.M. Ali, et al. Diamond & Related Materials 96 (2019) 67–73.

７．論文発表・特許（注：本課題に関連するこれまでの代表的な成果）▪ Hiroshi Naragino et al., Evergreen, 03, 1-5 (2016)▪ Mohamed Egiza et al., Evergreen, 03, 32-36 (2016)▪ Hiroshi Naragino et al., Jpn. J. Appl. Phys 55, 030302 (2016)▪ Hiroshi Naragino et al. Appl. Phys. A, 122, (2016).
▪ Mohamed Egiza et al. Coatings, 8, 359 (2018)▪ Ali M. Ali et al. Diamond relat. Mat. 96, 67 (2019)▪ A. M. Ali et al. Appl. Phys. Express 13, 065506 (2020).
８．キーワード（注：試料及び実験方法を特定する用語を２～３）
Nanodiamond, Coaxial arc plasma, negative bias, Hardness, near-edge X-ray absorption fine structure.

９．研究成果公開について① 論文（査読付）発表の報告（報告時期：2021 年 3 月）