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 ： 1908066S

Ｂ Ｌ 番 号 ： 12（様式第 5 号）

タ ン グ ス テ ン バ ッ フ ァ 層 を 有 す る 超 硬 合 金 基 板 及 び Si 基 板 上 に 堆 積
したナノダイヤモンドコンポジット膜の機械特性と化学結合構造との相関の解明
Study on relationship between mechanical properties and chemical bonding
structures of nanodiamond composite films deposited on cemented carbide withtungsten buffer layer and Si substrates
エ ギ ザ モ ハ メ ド ， ア リ モ ハ メ ド .ア リ , 田 中 佑 樹 , 星 野 光 一 朗 , 吉 武 剛
Mohamed Egiza, Ali M. Ali, Yuki Tanaka, Koichiro Hoshino, 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 Universit y※１
※２

※３
※４

先 端 創 生 利 用（ 長 期 タ イ プ ）課 題 は 、 実 施 課 題 名 の 末 尾 に 期 を 表 す （ Ⅰ ）、（ Ⅱ ）、（ Ⅲ ）を 追 記
してください。
利 用 情 報 の 公 開 が 必 要 な 課 題 は 、本 利 用 報 告 書 と は 別 に 利 用 年 度 終 了 後 2 年 以 内 に 研 究 成 果 公
開｛ 論 文（ 査 読 付 ）の 発 表 又 は 研 究 セ ン タ ー の 研 究 成 果 公 報 で 公 表 ｝が 必 要 で す (ト ラ イ ア ル
利 用 を 除 く )。
実験に参加された機関を全てご記載ください。
共 著 者 に は 実 験 参 加 者 を ご 記 載 く だ さ い （ 各 実 験 参 加 機 関 よ り 1 人 以 上 ）。

１．概要（注：結論を含めて下さい）
Ultrananocrystalline diamond/amorphous carbon composite (UNCD/a-C) films can be appliedin a variety of fields owing to their superior electrical, optical, and mechanical properties. The
high hardness and extremely smooth surface s of UNCD/a-C films as compared with those ofpolycrystalline diamond films are keys for the application to hard coating on cemented carbide
and silicon substrates, which are representative substrates for cutting tools and electronic
devices, respectively. UNCD/a-C films were deposited by coaxial arc plasma deposition(CAPD) on cemented carbide (WC-Co) substrates directly and with tungsten (W) buffer layers.
The films deposited on W buffer layers achieved an evident enhancement in the hardness to 56
GPa and Young’s modulus to 593 GPa, as compared with the hardness of 50 GPa and Young’smodulus of 520 GPa of films deposited directly on the substrate s. This significantimprovement in the mechanical properties is consistent with enhanced C-C sp 3 fractions in thefilms. It was found that the W buffer layers suppress Co catalytic effects that induces
graphitization.

２．背景と目的
Diamond and related hard carbon coatings haveattracted attention because they are effectively applicable
to cutting non-ferrous and abrasive materials due to theirunique features such as high hardness and excellent moldrelease. The physical properties of carbon materials arestrongly influenced by the ratio of sp3 (diamond-like) tosp2 (graphite-like) bonds. Ultrananocrystalline diamond/
amorphous carbon composite (UNCD/a-C) films
deposited on WC-Co at room substrate-temperature
exhibit the maximum hardness of 50 GPa and a modulusof 520 GPa [1]. It was demonstrated that low substratetemperature is effective to diamond growth andsuppressing the Co catalytic effects at the interface.
Furthermore, the diffusion of Co atoms into the films
hardly occurs even at the substrate temperature of 550 ºC.
To further understand the role of Co catalytic effects on
the properties of the films, W buffer layer was sputteredprior to the film deposition, because it was reported thatthe insertion of W buffer layer suppresses the catalytic
reactivity of transition metals for inducing graphitization[2, 3]. The effects of W buffer layer on the films growth,
the hardness, and Young’s modulus of the films werestudied. In addition, the chemical bonding structures ofthe films were investigated by X-ray photoemission
spectroscopy
andnear-edge
X-ray
absorption
fine-structure spectroscopies to understand the physicalorigin of the films properties due to insertion of W bufferlayer.

Fig. 1 Raman spectra of of UNCD/a-C films depositedon WC-Co substrates without W buffer layer.

Fig. 2 XPS survey of UNCD/a-C films on WC-Co
substrates (a) without and with W buffer layer.

３．実験内容（試料、実験方法、解析方法の説明）
WC–Co substrates (K-type cemented tungsten carbide)with a dimension of 10 × 4.5 mm were employed for film
deposition. The pretreatment by chemical etching for Co
removal near the substrate surface, which has been
essentially applied for the growth of CVD diamondcoatings on WC–Co, was not carried out in this study.
Only the pretreatment of roughening the substrates surface
was chemically made in the roughness average range of
0.15–0.2 μm to enhance the adhesion of the films. Prior to
the film deposition, the surfaces of the substrates wereFig. 3 C 1s X-ray photoemission spectra of UNCD/a-C
films deposited without W buffer layer.
cleaned in acetone and methanol ultrasonic bathes for
7 min, respectively.
UNCD/a-C films were deposited on WC-Co substrates atroom substrate-temperature by CAPD with pure graphite targets. The inside of a vacuum apparatus wasevacuated to base pressures of less than 10-4 Pa by a turbo molecular pump. An arc plasma gun equipped with a720 µF capacitor was operated at an applied voltage of 100 V. The films were deposited directly and with W
buffer layer sputtered at thickness of 100 nm. The hardness and Young’s modulus of the deposited films wereinvestigated by nano-indentation. The deposited films were characterized by X-ray photoemission
spectroscopic at beamline 12 of Kyushu Synchrotron.
４．実験結果と考察
The films deposited directly on WC-Co substrates exhibit a hardness of approximately 50 GPa and Young’s
modulus of 520 GPa. A Raman spectrum of the films is shown in Fig. 1. A peak detected at 1337 cm−1 might bedue to UNCD grains. The peak position is slightly shifted from that of bulk diamond peak (1333 cm−1 ) and its

peak is broaden, which might be due to phonon confinement effects and scattering in nano-sized grains anddue to the coexistence of D-band peak coming from a-C. Moreover, a broad peak around 1580 cm−1 wasobserved, which attributed to G-band of amorphous carbon matrices due to the bond stretching of carbon atoms
in sp2 hybridization. By the insertion of W buffer layer, the hardness and Young’s modulus were improved to56 GPa and 593 GPa, respectively. This improvement might be attributed to the suppression of Co catalytic
effects that induces films graphitization and in turn reduces films hardness and Young’s modulus. Also, theadhesion between UNCD/a-C film and WC-Co substrate was succesfly enhanced due to the buffer layer
enhanced the chemical compatibility between the film and substrate.
Figure 2 shows the elemental composition of UNCD/a-C films measured by XPS survey. O 1s and C 1s
peaks were detected, which indicates that the films are free of substrate contaminations. The O 1s peak is
attributed to the residual oxygen in the chamber during the films preparation and exposure to theenvironmental air after deposition [4]. Figure 3 shows the X-ray photoemission spectra of UNCD/a-C films,
which were decomposed to peaks by a software. The estimated sp3/(sp3+sp2) ratio is 60%, which show anagreement with the measured hardness and Young’s modulus and Raman spectra.
５．今後の課題
In this work, the role of W buffer layer in the suppression of Co catalytic effects, and the relationship between
the films hardness and C-C sp3 fraction were investigated. The results demonstrated that the insertion of thebuffer layer to form chemical compatibility can significantly increase the adhesion of UNCD/a-C films on WC-Co
substrates.

６．参考文献[1] Hiroshi Naragino et al. Appl. Phys. A, 122, (2016).
[2] Y.S. Li, A. Hirose, J. Appl. Phys. 101, 073503 (2007).
[3] Y.S. Li, A. Hirose, Surf. & Coat. Technol. 202, 280 (2007).
[4] Mohamed Egiza et al. Coatings, 8, 359 (2018)

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)
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, Raman, Hardness, XPS, X-ray photoemission spectroscopy, W buffer layer
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）