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 ： 1610090S

Ｂ Ｌ 番 号 ： BL12（様式第 5 号）

ハードコーティング材料への応用特化した炭素皮膜の軟 X 線分光分 析 II
Soft X-ray spectroscopic study on carbon films especially for hard coating applications II
エギザ モハメド，竹市悟志，野上智宏，工藤和樹，吉武 剛

Mohamed Egiza, Satoshi Takeichi, Tomohiro Nogami, Kazuki Kudo,
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

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）
Si-doped ultrananocrystalline diamond /amorphous carbon composite (UNCD/a-C) films weredeposited on cemented carbide (WC-Co) substrates for cutting tools applications by coaxial arc
plasma deposition (CAPD). The UNCD/a-C films exhibit a hardness of 50 GPa and a modulusof 520 GPa. To improve the mechanical and tribological properties of the UNCD/a-C films
further, the effects of Si doping was studied. Si-doped films deposited on WC-Co substrates
directly showed a degradation in the mechanical properties due to graphitization induced bythe diffusion of Co atoms from the substrates into the films. On the other hand, the Si -doped
films with a 1-m undoped UNCD/a-C buffer layers that block the diffusion of Co atoms into
the films shows an enhancement in the hardness and modules. It was found that the amount of
sp 3 bonds is evidently increased by Si doping from X-ray photoelectron and near-edge X-ray
absorption fine-structure spectroscopic measurements while the diffusion of Co into the films
is facilitated by Si doping.

２．背景と目的
Protective hard coatings to the WC-Co cutting tools are required in a variety of applications. Diamond andrelated hard carbon coatings have attracted attention because they are effectively applicable to cutting
non-ferrous and abrasive materials due to their unique features.1 The physical properties of carbon materials
are strongly influenced by the ratio of sp3 (diamond-like) to sp2 (graphite-like) bonds2. The mechanicalproperties of ultrananocrystalline diamond (UNCD)/amorphous carbon (a-C) composite (UNCD/a-C) films
comprising a large number of UNCD grains and an a-C matrix are expected to be strongly affected by the ratio
between sp3 and sp2 bonds. In our previous study, we succeeded in the growth of 50 GPa hardness and 520
GPa Young’s modules UNCD/a-C films with a thickness of more than 3 m by CAPD.3 They exhibited thesp3/(sp3+sp2) ratio of 69%, which was estimated from X-ray photoemission measurements.4
Si atoms do not form sp2 bonds but sp3 bonds in the chemical bonding. Thus, in the case of Si doping isapplied to carbon materials, it is expected that sp3 bonds such as C-Si sp3 bonds is preferentially formed.5 In
this work, the effects of Si doping on the deposition of UNCD/a-C films on WC-Co substrates was studied, andthe chemical bonding structures of the films were investigated by X-ray photoelectron and near-edge X-ray
absorption fine-structure spectroscopies.

３．実験内容（試料、実験方法、解析方法の説明）
Si-doped UNCD/a-C films were deposited on WC-Co substrates with dimensions of 10 mm diameter and 4mm thickness at room temperature by CAPD with 1 at.% Si blended graphite targets. The inside of a vacuum
apparatus was evacuated to base pressures of less than 10-4 Pa by a turbo molecular pump. An arc plasma gun
equipped with a 720 µF capacitor was operated at an applied voltage of 140 V. Three types of structural films
as shown in Fig. 1 were prepared. Concretely, Undoped UNCD/a-C films directly deposited on WC-Co
substrate, Si-doped UNCD/a-C films directly deposited on WC-Co substrates, and Si-doped UNCD/a-C films
deposited on approximately 1 m undoped UNCD/a-C interlayers were prepared. The hardness and modulusof the deposited films were investigated by nano-indentation. The deposited films were characterized bynanoindentation, EDX, SEM, and soft X-ray spectroscopic at beamline 12 of Kyushu Synchrotron.
1 at.% Si-doped
UNCD/a-C film

Undoped UNCD/a-C

1 at.% Si-doped
UNCD/a-C film

UNCD/a-C interlayer

WC-Co substrate

WC-Co substrate

WC-Co substrate

Sample-1

Sample-2

Sample-3

Fig.1 Schematic diagram of the deposited layers on WC-Co substrate

５．今後の課題
In this work, we could confirm the increased sp3 content
responsible for the enhanced hardness and Young’s modules ofthe Si-doped films deposited on the interlayers. From this, we aregoing to the effects of Si doping on the internal stress of the films
that is a key factor that determine the adhesion of the films on thesubstrates.

(a) Sample−1

sp3 ratio=69%
sp2 ratio=31%

sp

3C−O
C−O−C

sp

2

COOH

Intensity (arb. unit)

４．実験結果と考察
The undoped films (sample-1) deposited on WC-Co substrates
exhibit a hardness of approximately 50 GPa and modulus of 520
GPa. From X-ray photoemission spectra as shown in Fig. 2, thesp3 content was estimated to be 69%.
The Si-doped films (sample-2) directly deposited on theWC-Co substrates show a decrease in sp2 content. Since theenergy dispersive X-ray (EDX) spectra of the film exhibited thatCo atoms diffused into the films from the substrates, this isprobably because the Co atoms acts as catalysts that facilitategraphitization of sp3 bonds. The Si-doped films with theinterlayers exhibited no Co peaks in the EDX spectra as shown inFig. 3, which implies that the interlayer effectively block thediffusion of Co atoms from the substrate. The sp3 content wasestimated to be 72% from the X-ray photoemission spectra, andthe hardness and Young’s modules were 60 and 610 GPa,respectively. It was found that Si doping evidently enhances theformation of sp3 bonds, whereas it induces the diffusion of Co
atoms from the WC-Co substrates, which results in degradedhardness and Young’s modules..

(b) Sample−2
sp3 ratio=60%
sp2 ratio=35%
C-Si ratio=5%

sp

3sp

C−O
C−O−C2COOH(Si−C) sp(c) Sample−3

sp3 ratio=72%
sp2 ratio=23%
C-Si ratio=5%
C−O
C−O−C
COOH

290

sp3sp

2(Si−C) sp

Fig.2 XPS C1s spectrum of Si-doped
UNCD/a-C filmsCount (arb. unit)

Energy (keV)

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)

3285
Binding Energy (eV)

６．参考文献
1) A. Köpf , S. Feistritzer, K. Udier , Int. J. Ref. Metals & Hard
Mat. 24, 354-359 (2006).
2) J. Robertson, Progress Solid State Chem. 21, 199-333 (1991).
3) Hiroshi Naragino et al. Appl. Phys. A, 122, (2016).
4) Hiroshi Naragino et al. Jpn. J. Appl. Phys55, 030302 (2016).
5) X. M. He et al. J. Vac. Sci. Tech. A, 18, 2143 (2000).

3Fig.3 Top view EDX examination ofSi-doped UNCD/a-C film (sample-2)

280



Hiroshi Naragino et al. Appl. Phys. A, 122, (2016).

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, Hard coating, Coaxial arc plasma deposition, CAPD, Nanoindentation, Soft X-ray spectroscopic, Sidoping

９．研究成果公開について（注：※２に記載した研究成果の公開について①と②のうち該当しない方を消してください。また、論文（査読付）発表と研究センターへの報告、または研究成果公報への原稿提出時期を記入してください（2016 年度実施課題は 2018 年度末が期限となります）。
長期タイプ課題は、ご利用の最終期の利用報告書にご記入ください。

① 論文（査読付）発表の報告（報告時期：2019 年

3 月）