Local Structure Analysis on Si-Containing DLC Films Based on the Measurement of C K-Edge and Si K-Edge X-ray Absorption Spectra

Kanda, Kazuhiro; Suzuki, Shuto; Niibe, Masahito; Hasegawa, Takayuki; Suzuki, Tsuneo; Saitoh, Hedetoshi

doi:10.3390/coatings10040330

Cited by 14 publications

(9 citation statements)

References 41 publications

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“…This could be attributed to the surface hydration of the DLC layer that leads to the formation of trace quantities of byproducts containing COH, COO, and CO moieties . These results are consistent with NEXAFS analyses in the literature, which show evidence of the 1s → π* transitions associated with CC, CO, and CH moieties. ,− Such moieties are present at low concentrations (often below 0.1 wt %), and signals corresponding to the latter are not distinguished in the high-resolution XPS spectra of pristine DLC-coated PET material. Upon etching with argon for 50 s, the XPS spectra show a high C/O atomic ratio of ∼99:1 (Figure a,c and Table S1), manifesting the high near-surface carbon content of DLC coatings, which persists up to an argon-etching time of approximately 600 s (orange and blue vertical bands).…”

Section: Results and Discussionsupporting

confidence: 81%

Nanoscale Surface Compositions and Structures of Plasma-Modified Poly(ethylene terephthalate) Thin Films

et al. 2021

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Nanoscale compositions and structures of the plasma-treated surfaces of polymers often impart significant consequences on the barrier properties of thin films. Despite their technological importance for packaging and coating applications, a molecular-level understanding of their surface properties has been exceedingly challenging to obtain. This has been due to several factors, including their low external surface areas, nanometer-thin regions of surface modification, subtle differences between their surface versus bulk compositions, and the absence of long-range structural order. Nevertheless, recent advancements in solid-state nuclear magnetic resonance (NMR) spectroscopy, in particular using dynamic nuclear polarization (DNP) enhancement, in combination with X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT-IR) spectroscopy analyses provide detailed insights on the compositions of thin surface layers of plasma-modified poly(ethylene terephthalate) (PET) thin films. Analyses of 2D 13C{1H} DNP heteronuclear correlation (HETCOR) NMR spectra of plasma-modified PET films enabled signals from sp 3 carbon species associated with thin (30–80 nm) diamond-like carbon (DLC) surface layers to be detected and identified, along with their interactions at embedded DLC-PET interfaces. Complementary XPS spectra provide insights into different surface and subsurface elemental compositions of the plasma-modified PET films, which are corroborated by FT-IR analyses. Subsurface compositions and structures, in particular carbon:oxygen atomic ratios and intermixing of the DLC surface layers and PET regions, are shown to depend on plasma-enhanced chemical vapor deposition conditions, leading to different gas barrier properties of surface-modified PET films.

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Section: Results and Discussionsupporting

confidence: 81%

Nanoscale Surface Compositions and Structures of Plasma-Modified Poly(ethylene terephthalate) Thin Films

et al. 2021

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“…Hence, the peaks derived from sp 2 could be monitored separately from the peaks derived from sp 3 , thereby enabling determination of the sp 3 ratio with high accuracy [ 58 ]. The sp 3 ratio could be analyzed even when Si was introduced in DLC, and detailed studies have been conducted [ 59 ]. A series of FTIR measurements was performed to estimate the sp 3 ratios of DLC films.…”

Section: Methods Of Characterizationmentioning

confidence: 99%

Properties and Classification of Diamond-Like Carbon Films

Hiratsuka²,

et al. 2021

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Diamond-like carbon (DLC) films have been extensively applied in industries owing to their excellent characteristics such as high hardness. In particular, there is a growing demand for their use as protective films for mechanical parts owing to their excellent wear resistance and low friction coefficient. DLC films have been deposited by various methods and many deviate from the DLC regions present in the ternary diagrams proposed for sp3 covalent carbon, sp2 covalent carbon, and hydrogen. Consequently, redefining the DLC region on ternary diagrams using DLC coatings for mechanical and electrical components is urgently required. Therefore, we investigate the sp3 ratio, hydrogen content, and other properties of 74 types of amorphous carbon films and present the classification of amorphous carbon films, including DLC. We measured the sp3 ratios and hydrogen content using near-edge X-ray absorption fine structure and Rutherford backscattering-elastic recoil detection analysis under unified conditions. Amorphous carbon films were widely found with nonuniform distribution. The number of carbon atoms in the sp3 covalent carbon without bonding with hydrogen and the logarithm of the hydrogen content were inversely proportional. Further, we elucidated the DLC regions on the ternary diagram, classified the amorphous carbon films, and summarized the characteristics and applications of each type of DLC.

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“…The chemical environment around the absorbing atom can be evaluated from the positions of the absorption edge and the white line in the NEXAFS spectrum. The Si K edge shifts towards the higher energy side with increasing positive charge on the Si atom [ 45 , 46 ]. The edge from the hydrogenated Si-DLC film before irradiation was at ~1840 eV, i.e., near that of the Si wafer and a-Si:H film.…”

Section: Resultsmentioning

confidence: 99%

Effect of Soft X-ray Irradiation on Film Properties of a Hydrogenated Si-Containing DLC Film

et al. 2021

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The effect of soft X-ray irradiation on hydrogenated silicon-containing diamond-like carbon (Si-DLC) films intended for outer space applications was investigated by using synchrotron radiation (SR). We found that the reduction in film thickness was about 60 nm after 1600 mA·h SR exposure, whereas there was little change in their elemental composition. The reduction in volume was attributable to photoetching caused by SR, unlike the desorption of hydrogen in the case of exposure of hydrogenated DLC (H-DLC) film to soft X-rays. The ratio of the sp2 hybridization carbon and sp3 hybridization carbon in the hydrogenated Si-DLC films, sp2/(sp2 + sp3) ratio, increased rapidly from ~0.2 to ~0.5 for SR doses of less than 20 mA·h. SR exposure significantly changed the local structure of carbon atoms near the surface of the hydrogenated Si-DLC film. The rate of volume reduction in the irradiated hydrogenated Si-DLC film was 80 times less than that of the H-DLC film. Doping DLC film with Si thus suppresses the volume reduction caused by exposure to soft X-rays.

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Local Structure Analysis on Si-Containing DLC Films Based on the Measurement of C K-Edge and Si K-Edge X-ray Absorption Spectra

Cited by 14 publications

References 41 publications

Nanoscale Surface Compositions and Structures of Plasma-Modified Poly(ethylene terephthalate) Thin Films

Nanoscale Surface Compositions and Structures of Plasma-Modified Poly(ethylene terephthalate) Thin Films

Properties and Classification of Diamond-Like Carbon Films

Effect of Soft X-ray Irradiation on Film Properties of a Hydrogenated Si-Containing DLC Film

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