田中 一平

This study discusses the fabrication of amorphous silicon carbon nitride (a-SiCN) films by ion-beam-assisted deposition (IBAD) and investigates their hardness and frictional properties. The a-SiCN films are deposited by IBAD via electron beam evaporation of graphite and Si under simultaneous nitrogen ion-beam bombardment at acceleration voltages of 0–15 kV. The a-SiCN films are deposited at acceleration voltages of 0, 0.2, 10, and 15 kV. The films are not deposited via nitrogen ion-beam irradiation at 0.5 or 1.0 kV. The a-SiCN films deposited at 0, 0.2 and 15 kV are primarily composed of C. However, the a-SiCN films deposited at 10 kV are primarily composed of Si. The chemical bond of the a-SiCN films, measured via X-ray photoelectron spectroscopic analysis, is dominant in the C[dbnd]C bonds in the C1s spectra. The a-SiCN film deposited at 0 kV demonstrates a hardness value of 19.5 GPa, whereas the a-SiCN films deposited at 0.2, 10 and 15 kV exhibit hardness values in the range of 25–34 GPa. The hardness of the a-SiCN films depended on the ion beam acceleration voltages. The friction coefficient of the a-SiCN film with a high C[dbnd]C bond content against a steel ball is as low as 0.07. In summary, the a-SiCN films deposited with a high-energy ion beam of 15 kV exhibit a high hardness level and a low friction coefficient.

Microwave sheath-voltage combination plasma (MVP) represents a new method to generate plasma and coat diamond-like carbon films onto the three-dimensional metal surfaces. The present work investigates the synthesis of diamonds using MVP deposition, focusing in particular on how pressure and bias voltage affect the diamond structure. Using MVP, silicon wafers were coated with diamond in gas mixtures of methane and hydrogen with the substrate bias ranging from 0 to −200 V and pressure ranging from 800 to 1000 Pa. Although diamond particles are created with the substrate biased between 0 and −200 V at 1% methane concentration, at −200 V the particles are affixed atop Si or SiC cones that form on the Si substrate due to plasma etching. X-ray diffraction analysis reveals that the diamond structure is created up to a bias voltage of −100 V at 3% methane concentration. Nanodiamond is produced at methane concentration of 3%. These experiments suggest that MVP, a new diamond coating method, makes depositing the diamond on 3D shape substrates possible.

The formability of the corrugated cup was investigated by the deep drawing process. Deep drawing, which is one of press forming, is a plastic processing technology for forming a thin plate into a three-dimensional container or case. For container products, there are many products formed by this technology. Depending on the application, the functionality of the container itself was required. For example, there are embossing, thickening, and tailored blanks processing. In the present study, corrugated cup was formed to enhance the functionality of the cup. A unique die was used to form the cup having a corrugated shape. The shoulders of the die were grooved, and the steel balls were arranged without gaps in the groove. The balls rotated freely during forming. In an experiment, the blanks were commercially extra-low carbon steel SPCC and stainless steel SUS304. The initial diameter and thickness of the blank were 70 to 95 mm and 0.3 to 0.5 mm. The lubricant was the solid powders of molybdenum disulfide. The deep drawing process was performed using an oil hydraulic press at a forming speed of approximately 10 mm/min. The diameter of the punch was 40 mm, and the smallest hole diameter of the die was 41 mm. These tools were tool steel SKD11, and were standard heat treated. The metal sheets were successfully drawn without the cracks. In the side wall of the cup, the distance between the waves was approximately 8.6 mm. The thickness strain at the bottom of the drawn cup SPCC was no more than 0.1.

© 2018 Elsevier B.V. Crystalline carbon nitride is expected to be an emitter with a long lifetime and high emission stability, because it is composed of carbon and nitrogen with high oxidation resistance and its sharp shape facilitates the occurrence of electron emission. The purpose of this paper is to clarify the field emission properties of crystalline carbon nitride. We studied the improvements in the field emission properties of carbon nitride after surface treatments. The carbon nitride was synthesized using microwave plasma chemical vapor deposition from a CH4-N2 gas system. Si substrates with different electrical properties (p- and n-type of 0.01 and 1500 Ω respectively) were used. The carbon nitride on the 0.01 Ω n-type substrate showed the highest current density of approximately 0.25 mA/cm2. The maximum current densities of the carbon nitride on the n-type or p-type substrates were higher than those of the undoped type by decreasing the resistivity of the substrate. The threshold field (emission current observed in the minimum electric field) of the carbon nitride on n-type substrates was decreased by decreasing the substrate resistance. In the case of Au-coated deposits on an n-type Si substrate of 0.01 Ω a threshold field was observed at approximately 1 V/μm. In addition, the electric field emission current density at 20 V/μm was 0.83 mA/cm2. The ultra-thin coatings of Au on the carbon nitride were effective in decreasing the threshold field and increasing the maximum current density. The Fowler-Nordheim plots of the carbon nitride with or without Au coatings formed a straight line, indicating that the Fowler-Nordheim theory perfectly fit the field emission behaviors of samples.

© 2018 The Japan Society of Applied Physics. Si-doped diamond-like carbon (a-C:H:Si) films can be deposited at an ultra-high rate around 100 μm h-1 by using microwave sheath-voltage combination plasma (MVP), showing a friction coefficient of 0.05-0.1 similar to that of conventional a-C:H:Si films. However, the effect of humidity on the friction property of a-C:H:Si films deposited by MVP has not been studied. Thus, we investigate the frictional characteristics of a-C:H:Si films deposited on different duty ratios of 10, 30, and 50% using MVP, where a steel ball is slid against an a-C:H:Si film under dry conditions with 10%-50%RH. The a-C:H:Si film deposited on the low duty ratio of 10% became a polymeric structure. The friction coefficients of the a-C:H:Si films decreased with a decrease in the relative humidity. At the low relative humidity of 10%, it was shown that low friction below 0.06 is achieved by transfer film with the amorphous carbon structure formed on the mating ball.

Recently, with increasing demands for energy saving via friction reduction and lifetime extension via wear reduction, the applications of diamond-like carbon (DLC) are spreading gradually and steadily. It should be noted that the typical coating speed of DLC with such a conventional plasma chemical vapor deposition (CVD) is not very high, similar to 1 mu m/h, due to the employment of low-density plasma. In our previous work, we proposed that the plasma CVD with MVP (Microwave-sheath Voltage combination Plasma) is capable of coating a Si-containing DLC (Si-DLC) film at larger than 100 mu m/h. In this work, for achieving the design principle of Si-DLC by MVP, we studied the effects of process gas, which is a mixture of TMS, Ar, and one hydrocarbon gas, on the relationship between the film structure and the mechanical properties of Si-DLC films prepared by MVP. Si-DLC films were deposited by MVP with a hydrocarbon gas, CH4 or C2H2, where the TMS (tetramethylsilane)/hydrocarbon gas ratio was changed. The structure of DLC was estimated by Raman spectroscopy. The atomic composition of the films was evaluated by XPS for C, O, and Si, and RBS-ERDA for H/C. Friction tests were conducted using a ball on-disk apparatus under dry condition. Si concentration in the films increased linearly with an increasing TMS/hydrocarbon ratio for both hydrocarbon gases, being the determining factor for the I-D/I-G ratio and SiC concentration of Si-DLC. In other words, we can determine the ID/IG ratio and SiC bond concentration in Si-DLC by controlling the TMS/hydrocarbon ratio. In addition, much higher deposition speed and higher H concentration are obtained by MVP using C2H2 than CH4. These findings, or the effect of gas source on the film structure of Si-DLC by MVP, would be an important design principle in designing Si-DLC for desired film structure and hardness, and better tribological performance.

<p>Graphitic carbon nitride (g-C₃N₄) is one of the metal-free photocatalyst materials. Investigation was carried out on the synthesis of g-C₃N₄ films by thermal CVD using melamine. A thermal chemical vapor deposition apparatus of the hot-wall type was used for g-C₃N₄ film deposition on a Si substrate. Melamine was used as the feedstock. The heating temperatures of the substrate were varied from 773 to 973 K. The g-C₃N₄ films were analyzed by SEM, XRD, Raman spectroscopy, FT-IR, and XPS. The thickness of the deposited films at a heating temperature of 873 K was from 0.6 to 1.0 µm. A peak of g-C₃N₄ was observed in the XRD patterns at heating temperatures of 873 and 973 K. From FT-IR and XPS, C and N bonds were observed at a heating temperature of 873 K. We concluded that g-C₃N₄ films of thickness 0.6 to 1.0 µm were obtained at a heating temperature of 873 K.</p>

Investigation of the low temperature synthesis of carbon nitride was carried out by microwave plasma CVD. Carbon nitride was synthesized using an improved microwave plasma CVD apparatus. Si was used as the substrate. A mixture of CH4 and N-2 gas was used as a reaction gas. Synthesis pressure was varied from 1.1 to 4.0 kPa, microwave power was varied from 400 to 800W. Faceted particles were obtained at a microwave power of 800W and a substrate temperature of 880 K. Faceted particles were obtained at various synthesis pressures and a substrate temperature of as low as 740 K. Also, beta-Si3N4 and alpha-C3N4 peaks were observed in the X-ray diffraction (XRD) pattern. As a result of studies of the low-temperature synthesis of carbon nitride by microwave plasma CVD, the morphology of deposits was found to depend on substrate temperature, and faceted particles were obtained at a substrate temperature as low as 740 K. (C) 2016 The Japan Society of Applied Physics

Carbon nitride, which has fascinating properties such as high hardness and high current density of field emission, was investigated to elucidate the tribological properties of carbon nitride synthesized using microwave plasma CVD against CVD diamond. Carbon nitride was synthesized using microwave plasma CVD with a mixture of CH4-N2 gas used as a reaction gas. The CH4 flow rate was varied from 1 to 3 SCCM. Using a ball-on-disk friction tester, tribological properties of the deposits were estimated. Counterpart materials were CVD diamond film coated onto the SiC ball using microwave plasma CVD. Regarding the estimation of tribological properties, the lowest coefficient of about 0.05 against diamond was obtained for deposits made with a CH4 flow rate 2 SCCM. The wear depth was shallow against deposits synthesized in a CH4 flow rate of 2 SCCM. Results demonstrate that tribological properties of carbon nitride against diamond had a low friction coefficient. Deposits synthesized in a CH4 flow rate of 2 SCCM exhibited the shallowest wear depth.

マイクロ波プラズマCVDにより合成した窒化炭素のトライボロジー特性に及ぼす合成時のCH₄流量の影響ついて検討した．AESによる表面元素分析により生成物の窒素含有率がCH₄流量を変化させることにより増加した．トライボロジー特性評価を行った結果，窒素含有率の高い生成物は相手材にSUJ2を用いた場合に高い耐摩耗性を有し，相手材攻撃性が低下することが明らかとなった．