Characterization of Hydrogen-Free and Hydrogenated DLC Films
Diamond-like carbon (DLC) films are an amorphous carbon film with sp2 and sp3 bonding structures of carbons. The DLC films have been used widely in industry owing to have superior properties such as high mechanical hardness and low friction coefficient. T
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Characterization of Hydrogen-Free and Hydrogenated DLC Films Toru Harigai, Takahiro Imai, Hirofumi Takikawa, Satoru Kaneko, Shinsuke Kunitsugu, Masahito Niibe, Kazuhiro Kanda, and Masao Kamiya
3.1 Introduction Diamond-like carbon (DLC) films are a hard amorphous carbon film. DLC films with excellent properties mechanically, electrically, optically, and chemically are widely used in industry. Basically, the DLC films contain only carbon or carbon and T. Harigai (B) · T. Imai · H. Takikawa Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku, Toyohashi, Aichi 441-8580, Japan e-mail: [email protected] T. Imai e-mail: [email protected] H. Takikawa e-mail: [email protected] S. Kaneko Kanagawa Institute of Industrial Science and Technology, 705-1 Shimoimaizumi, Ebina, Kanagawa 243-0435, Japan e-mail: [email protected] S. Kunitsugu Industrial Technology Center of Okayama Prefecture, 5301 Haga, Okayama, Okayama 701-1296, Japan e-mail: [email protected] M. Niibe · K. Kanda University of Hyogo, 3-1-2 Koto, Kamigori-cho, Ako-gun, Hyogo 678-1205, Japan e-mail: [email protected] K. Kanda e-mail: [email protected] M. Kamiya Itoh Optical Industrial Co., Ltd., 3-19 Miyanarityo, Gamagori, Aichi 443-0041, Japan e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2021 S. Kaneko et al. (eds.), Carbon Related Materials, https://doi.org/10.1007/978-981-15-7610-2_3
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Fig. 3.1 DLC films on ternary phase diagram of bonding in amorphous carbon films [1, 2]
sp2
H
hydrogen as constituent elements. Carbons in the DLC films are thought to form sp2 and sp3 bonding structures in the amorphous structure [1]. The abundance ratio (sp3 fraction) of sp2 and sp3 bonding structures and hydrogen content in the DLC films are important parameters determining the film properties of the DLC films. DLC films are divided into a hydrogen-free DLC film and a hydrogenated DLC film from the content of hydrogen in the film and is further often classified into four types from the difference in the sp3 fraction. In the hydrogen-free DLC films, the films with high and low sp3 fraction are called a tetrahedral amorphous carbon (ta-C) film and an amorphous carbon (a-C) film, respectively. Similarly, the hydrogenated DLC films are divided into a tetrahedral hydrogenated amorphous carbon (ta-C:H) film and a hydrogenated amorphous carbon (a-C:H) film. Figure 3.1 shows the positioning of four types of DLC films in carbon films composed of carbon and hydrogen. ta-C films have extremely high mechanical hardness comparable to diamond [3]. The ta-C films also having excellent mechanical properties such as high surface flatness and low friction coefficient [4, 5] are useful as a protective film for cutting tools and molds [5–7]. The a-C films, which is softer than the ta-C films, can be expected to improve electrical conductivity due to increased sp2 bonding structures. It has been reported that hydrogenated DLC films have high biocompatibility [8, 9]. Not all
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