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 ： 2212136S

Ｂ Ｌ 番 号 ： 12（様式第 5 号）

同軸型アークプラズマ成膜法で作製したナノダイヤモンド薄膜の化
学結合状態が上皮細胞の付着に与える影響と歯科インプラントへの応用
Effects of Chemical Bonding Structure of Nanodiamond Thin Films Deposited byCoaxial Arc Plasma Deposition on Adhesion of Epithelial Cells and Application toDental Implants
Lama Osman, 楢 木 野宏, 長野里基，齊藤

誠志郎，吉武剛

Lama Osman, Hiroshi Naragino, Satoki Nagano, and Tsuyoshi Yoshitake
九州大学大学院総合理工学研究院

Interdisciplinary Graduate School of Engineering Sciences, Kyushu University※１※２※３※４

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１．概要（注：結論を含めて下さい）
This study focused on the fabrication of hard nanodiamond composite films (NDC)on titanium(Ti) substrates under negative bias voltages using hybrid coaxial arc plasma deposition(CAPD). The deposition process was carried out with varying substrate bias voltages and apure graphite target, without any inserted gases, at a pressure of 10 -5 Pa. The effects of thesubstrate bias voltage on the deposition process, as well as the mechanical and structuralproperties of the films, were investigated. It was found that at an optimal bias voltage of -40 V,
accelerated positive carbon ions facilitated favorable deposition conditions for nanocrystalline
diamond growth, resulting in hard films with superhardness of 96 GPa which is close todiamond gem. The study also employed X-ray photoelectron and near edge X-ray absorption
fine structure spectroscopies to confirm the enhancement of sp 3 -C hybridization carbon in thedeposited films with 89%, which was consistent with the improved mechanical properties due
to enhanced C 1s (σ*) transitions. The adhesion, growth, differentiation and osseointegrationof epithelial cells are expected to be significantly improved in dental implants due to thehighly biocompatible diamond content (89%) proposed by these films. The improved celladhesion is caused by the organic layer adsorbed on the films from the cell medium.
The adsorbed layer has greater adhesion to NDC films’ surface due to strong
diamond surface dipoles that could be generated by further hydrogen or oxygensurface termination. Therefore, the NDC coatings supported epithelial cells better
than the reference Ti substrate.

２．背景と目的
Nanodiamond composite (NDC) films nowadays have grabbed global researchers’ attention. Comprisingdiamond crystallites (less than10 nm in diameter) within an amorphous carbon vicinity imparts in them meritproperties. Synergistic mechanical, tribological, and biocompatible features of NDC films are thoughtprovoking for implants and artificial joints. Fundamentally, NDC films have superior biocompatibility as oneof the most practical carbon allotropes which is the principal constituent of a living organism.
Jointly, pure titanium (Ti) is the broadly utilized implant candidate because of its exceptional lightness,
strength, corrosion resistance, and biocompatibility However, Ti partially endures bio-tribocorrosion upon
biological enclosure, causing Ti debris ejection into surrounding tissues, and their systemic dissemination andprecipitation in distant organs. Mutual implant–organism reactivity leads to aseptic loosening (bone resorption
and poor osseointegration) and bacterial infection. As a consequence, patients bear pain, allergic reactions, andinflammation resulting in implant failure and costly revision surgeries. One promising solution, is protective
diamond film implementation to Ti implants for their bio-tribocorrosion and osseointegration enhancement.

In our pervious study, we acquired impressing mechanical and structural properties of the NDC films on Ti via

a hybrid system of ion etching gun and coaxial arc plasma deposition (IG/CAPD) at room temperature.

Motivated by the results, in this study we implement the application of negative bias voltages during thegrowth of NDC films on Ti. The influence of the applied variable bias voltage was further investigated in termsof mechanical and structural characterization. The application of the negative bias voltages during the growthof NDC films is expected to reinforce the sp3-fraction of the films by selective etching of sp2-C bonded atoms
by the highly energetic C+ ions accelerated from the plasma towards the Ti substrates where they are quenched
into sp3-C bonded atoms. The higher content of diamond in the films is expected to improve the adhesion
strength of epithelial cells to the UNCD films due to their excellent biocompatibility and strong surface energy.
The surface energy can be modified by terminating the surface with oxygen, nitrogen, or fluorine, which could
facilitate the growth and differentiation of stem cells into various human body cells. In vitro investigation of
the improved mechanical and structural NDC films are under investigation jointly with Kyushu University
Hospital.
３．実験内容（試料、実験方法、解析方法の説明）

substrates using the hybrid IG/CAPD system with a graphite target atbase pressures less of 10-5 Pa. The film deposition was carried out on
Ti substrates with dimensions of 10×10 mm. Different bias voltages
were applied to the substrate holder from 0V to -100 V during
deposition with the arc plasma gun, that is equipped with a 720 µF
capacitor, and with a discharge repetition rate of 1 Hz. The films'

4

Load (mN)In this study, NDC films were deposited on negatively biased Ti

5

[0 V]
[-20 V][-40 V][-60 V][-80 V][-100 V]

32
1

0
0.00

0.02

0.04

0.06

0.08

Indentation depth (µm)

Fig.1. Load-displacement curves of NDC
films on Ti.

hardness and Young's modulus were evaluated by nanoindentation with an applied indentation load of 0.5
mN/10 s, while the adhesion strength was assessed by a scratch test. The chemical bonding structures of thefilms were characterized using X-ray photoelectron and near edge X-ray absorption fine structure (NEXAFS)
spectroscopies.

spectroscopy has been conducted for NDC films at different bias
voltages. At lower bias voltages, the spectra tend to slightly shift
to lower binding energies with respect to C 1s peak at 285.5 eV
which may result in more sp2-C bonded atoms in the films. At theoptimal bias voltage of -40V, the spectra have the highest
tendency to shift towards the higher binding energies whichindicates more sp3-C fraction in the films of 89% calculated by

Normalized intensity (a.u.)

Critical Load (N)

４．実験結果と考察
Critical Load50
The nanoindentation load-displacement curves, as illustrated in Fig.1,
were utilized to evaluate the hardness of the fabricated films. The40
results showed that increasing the bias voltage led to a corresponding
30
increase in both hardness and Young's modulus. At a bias voltage of20-40 V, the hardness was drastically improved to be 96 GPa which is
10comparable to diamond gem. The negative bias voltage of the0substrate played a crucial role in enhancing the mechanical properties
0-20-40-60-80-100of the films, especially the hardness. This was attributed to theNegative bias voltage (V)electrical attraction of positively charged carbon species to the Fig.2. Adhesion strength of NDC films on Ti.
negatively biased substrates. The scratch test was employed toevaluate the adhesion strength of the UNCD/a-C films, as depicted in Figure 2. The critical loads of the NDC
films fabricated at different bias voltages indicated a remarkable improvement in the adhesion strength withincreasing negative bias voltage. The critical load of the films fabricated for the unbiased film was found to be
16 N, which increased significantly to 48 N when fabricated at the optimal bias voltages of -40 V. This is
attributed to a formation of a TiC interfacial layer due to highly energetic C+ ions that is sub-implanted
underneath Ti substrate’s surface.
C 1s-100 V
284.5 eVFor a complementary structural analysis, C 1s photoemission-80 V292-60 V-40 V-20 V0V
290288286284282280

Binding energy (eV)Fig.3. C 1s photoemission spectra of NDC films onTi.

deconvolution of C 1s photoemission spectra into component peaks using Voigt function. Theses results areconsistent with the superhardness of the films of 96 GPa at the optimal bias voltage of -40V.
５．今後の課題
In this study we obtained novel superhardness of the NDC films at an optimal bias voltage of -40V. The
significant increase in the hardness of the films at this optimal bias voltage is correlated to increased sp3-C
fraction in the films which is synergistically enhanced by the sub-implantation of the highly energetic C+ ions
underneath Ti substrate’s surface. These remarkable results are expected to promote interesting adhesion andosseointegration of the epithelial cells due to the highly biocompatible diamond content in the films (89%) for
the application in dental implants. In vitro investigation of the optimal NDC films are currently progressedwith cooperation with Kyushu University Hospital..
６．参考文献[1] Osman, Lama, et al. "Adhesion of nanodiamond composite films on Ti substrates at room temperature
via hybrid ion etching gun and coaxial arc plasma deposition." Applied Physics Express 15.11 (2022):
115004.
[2] Ali, Ali M., et al. "Negative bias effects on deposition and mechanical properties of ultrananocrystalline
diamond/amorphous carbon composite films deposited on cemented carbide substrates by coaxial arcplasma." Diamond and Related Materials 96 (2019): 67-73.
[3] Naragino, Hiroshi, et al. "Hard coating of ultrananocrystalline diamond/nonhydrogenated amorphous
carbon composite films on cemented tungsten carbide by coaxial arc plasma deposition." Applied Physics
A 122 (2016): 1-10.
[4] Zkria, Abdelrahman, et al. "Structural evolution of laser-irradiated ultrananocrystalline
diamond/amorphous carbon composite films prepared by coaxial arc plasma." Applied Physics
Express 13.10 (2020): 105503.

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）
該当なし
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 composite films, Negative bias growth, Titanium, Coaxial arc plasma deposition
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論文（査読付）発表の報告（報告時期：2025 年 3 月）