Influence of the source gas ratio on the hydrogen and deuterium content of a-C:H and a-C:D films: Plasma-enhanced CVD with CH₄/H₂, CH₄/D₂, CD₄/H₂ and CD₄/D₂

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• 作者：K. Ozeki^a ; ^{ozeki@mx.ibaraki.ac.jp} ; D. Sekiba^b ; T. Suzuki^c ; K. Kanda^d ; M. Niibe^d ; K.K. Hirakuri^e ; T. Masuzawa^a
• 关键词：Amorphous hydrogenated carbon ; Deuterium ; Hydrogen ; ERDA ; RBS ; NEXAFS ; Hardness
• 刊名：Applied Surface Science
• 出版年：2013
• 出版时间：15 January, 2013
• 年：2013
• 卷：265
• 期：Complete
• 页码：750-757
• 全文大小：554 K

文摘

Amorphous hydrogenated carbon (a-C:H) and amorphous deuterated carbon (a-C:D) films were prepared using plasma-enhanced chemical vapor deposition (PECVD) from CD₄, H₂, CD₄ and D₂ source gases. Fourteen different samples were prepared by changing the source gas ratios of CH₄/H₂, CH₄/D₂, CD₄/H₂, and CD₄/D₂. The concentrations of hydrogen (H) and deuterium (D) relative to carbon (C) in the films were determined by elastic recoil detection analysis (ERDA) and Rutherford backscattering spectroscopy (RBS). The sp²/(sp² + sp³) ratios of the films were analyzed by near-edge X-ray absorption fine structure (NEXAFS) measurements. Hardness and mass density of the films were measured using a nanoindenter and X-ray reflectivity (XRR), respectively. For all combinations of source gas, the H and D concentrations varied by only 4.0 at. % . For the CH₄/D₂ source gas, the D concentration in the film increased from 0 at. % with the D₂/(CH₄ + D₂) source gas combination to 11.2 at. % for the 80 % D₂/(CH₄ + D₂) source gas combination. The increase in D concentration exceeded the increase in total H and D concentration (3.4 at. % ). For CH₄/D₂ source gas, the H concentration decreased as the D concentration increased. For the CD₄/H₂ source gas, we observed the opposite tendency. Additionally, an isotope effect between the a-C:H films and the a-C:D films was observed, with preferential incorporation of H over D. From the NEXAFS measurements, the sp²/(sp² + sp³) ratios in all of the samples were between 38.8 % and 40.8 % . A correlation between the sp²/(sp² + sp³) ratio and the H₂ or D₂ gas source ratio was not observed. The hardness and density of the films decreased when the H₂ or D₂ source gas ratio increased. Even though the H concentration in the a-C:H films was higher than the D concentration in the a-C:D films, the a-C:D films had lower hardness and mass density values. These findings suggest that information concerning the voids, nanostructures, sp²/sp³ ratios and H concentrations of hydrogenated amorphous carbon films is crucial for evaluation of their mechanical properties.