神田 一浩

Abstract Positron annihilation spectroscopy was used to investigate vacancy-type defects in diamond-like carbon (DLC) films. From Doppler broadening measurements of the γ-rays produced by annihilation and positron annihilation lifetime (PAL) using a slow positron beam on DLC films deposited by various deposition methods and conditions, it was found that there is a good correlation between the S parameter obtained by Doppler broadening and PAL. The result of PAL correlates well with film density and hardness, indicating that PAL measurements can be used as an indicator of these film properties. The hydrogen content in the DLC film was roughly proportional to the PAL. However, there were also cases in which PAL differed greatly even with almost the same hydrogen content, and the sp²/(sp²+sp³) ratio of carbon in DLC films has no direct relationship with PAL.

<jats:title>Abstract</jats:title> <jats:p>The effects of soft X-ray irradiation and atomic hydrogen annealing (AHA) on the reduction of graphene oxide (GO) to obtain graphene were investigated. To clarify the interaction between soft X-rays and GO, soft X-rays of 300 eV and 550 eV were used for C 1s and O 1s inner-shell electron excitation, respectively at the NewSUBARU synchrotron radiation facility. Low-temperature reduction of the GO film was achieved by using soft X-ray at temperatures below 150 °C at 300 eV, and 60 °C at 550 eV. O-related peaks in X-ray photoelectron spectroscopy, such as the C–O–C peak, were smaller at 550 eV than those at 300 eV. This result indicates that excitation of the core–shell electrons of O enhances the reduction of GO. Soft X-rays preferentially break C–C and C–O bonds at 300 and 550 eV, respectively.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The reduction of graphene oxide (GO) through atomic hydrogen annealing (AHA) and soft X-ray irradiation is investigated using microwell substrates with μm-sized holes with and without Ni underlayers. The GO film is reduced through AHA at 170 °C and soft X-ray irradiation at 150 °C. In contrast, some GO films are not only reduced but also amorphized through soft X-ray irradiation. The effect of the Ni underlayer on GO reduction differs between AHA and soft X-ray irradiation. In AHA, the difference in GO reduction between SiO<jats:sub>2</jats:sub> and Ni underlayer was originated from the atomic hydrogen density on sample surface. On the other hand, in soft X-ray irradiation, the difference in GO reduction between SiO<jats:sub>2</jats:sub> and the Ni underlayer originates from the excited electrons generated by soft X-ray irradiation. Reduction without damage is more likely to occur in the suspended GO than in the supported GO.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A demonstration test of a newly developed double crystal monochromator was performed on beamline BL06 in the NewSUBARU synchrotron radiation facility of Hyogo University. Due to the symmetrical layout of the 1st crystal and 2nd crystal units of the monochromator, a maximum rotation speed of the main axis of up to 5.0 degrees/sec could be achieved. The monochromator is controlled by a newly developed control board programmed with an electronic cam algorithm. The control system allows the speed of both Z<jats:sub>1</jats:sub> and Z<jats:sub>2</jats:sub> axes to be successively synchronized as the Bragg angle changes. The <jats:italic>Z</jats:italic> <jats:sub>1</jats:sub> and <jats:italic>Z</jats:italic> <jats:sub>2</jats:sub> axes are moved apart by equal amounts from the center of gravity of the monochromator as the Bragg angle is increased. Also, the speed at which the Z<jats:sub>1</jats:sub> and Z<jats:sub>2</jats:sub> axes are moved apart increases with larger Bragg angle. This newly developed monochromator can maintain a stable exit beam height just as well as previous mechanical cam type monochromators proved on the height of the exit beam measured by an encoder system and observed by fluorescent screen. Due to the symmetrical layout and newly developed control system, the monochromator is suitable for industrial use because it can handle a wide energy range and allows high-throughput experiments to be carried out.</jats:p>

Silicone tubing is used in small-diameter long-sized tubes for medical applications, such as urinary catheters. However, bacteria in urine adhere to the catheters, forming colonies and biofilms and resulting in blockages and urinary tract infections. Therefore, we have reported a method of AC high-voltage plasma chemical vapor deposition to prevent bacterial adhesion by depositing diamond-like carbon (DLC) on a lumen of a silicone catheter and smoothing the surface. However, the sp3/sp2 structure of DLC on the lumen surface is unresolved, and biomimetic DLC with a functionalized surface has not been investigated. Therefore, we analyzed a flexible membrane structure that can deform as the resin tube deforms. In addition, we developed a lumen surface-modification method using an AC high-voltage burst oxygen plasma processing to bring the DLC surface closer to the in vivo environment. We succeeded in creating biomimetic DLC and introducing carboxyl groups. Using this technology, the surface functionalization of medical tube materials is biocompatible with various protein-adsorption properties.

Soft X-rays excite the inner shells of materials more efficiently than any other form of light. The investigation of synchrotron radiation (SR) processes using inner-shell excitation requires the beamline to supply a single-color and high-photon-flux light in the soft X-ray region. A new integrated computing multi-layered-mirror (MLM) monochromator was installed at beamline 07A (BL07A) of NewSUBARU, which has a 3 m undulator as a light source for irradiation experiments with high-photon-flux monochromatic light. The MLM monochromator has a high reflectivity index in the soft X-ray region; it eliminates unnecessary harmonic light from the undulator and lowers the temperature of the irradiated sample surfaces. The monochromator can be operated in a high vacuum, and three different mirror pairs are available for different experimental energy ranges; they can be exchanged without exposing the monochromator to the atmosphere. Measurements of the photon current of a photodiode on the sample stage indicated that the photon flux of the monochromatic beam was more than 10¹⁴ photons s⁻¹ cm⁻² in the energy range 80–400 eV and 10¹³ photons s⁻¹ cm⁻² in the energy range 400–800 eV. Thus, BL07A is capable of performing SR-stimulated process experiments.

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.

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.

In this paper, the local structure of silicon-containing diamond-like carbon (Si-DLC) films is discussed based on the measurement of C K-edge and Si K-edge near-edge x-ray absorption fine structure (NEXAFS) spectra using the synchrotron radiation of 11 types of Si-DLC film fabricated with various synthesis methods and having different elemental compositions. In the C K-edge NEXAFS spectra of the Si-DLC films, the σ* band shrunk and shifted to the lower-energy side, and the π* peak broadened with an increase in the Si content in the Si-DLC films. However, there were no significant changes observed in the Si K-edge NEXAFS spectra with an increase in the Si content. These results indicate that Si–Si bonding is not formed with precedence in Si-DLC film.

The effects of soft X-ray irradiation on fluorinated diamond-like carbon (F-DLC) films were investigated using synchrotron radiation (SR). The Vickers hardness of the F-DLC films substantially increased from an initial value of about 290 to about 800HV at a dose of 50 mA.h and the remained constant at about 1100 HV at doses of more than 300 mA.h. This dose dependence was consistent with those of the film thickness and elemental composition. The depth profile of the elemental composition inside each F-DLC film obtained by the measurement of the X-ray photoelectron spectrum (XPS) during sputtering showed that the composition ratio of fluorine was approximately constant from the surface to the neighborhood of the substrate. Namely, fluorine atoms were desorbed by SR irradiation from not only the surface but also the substrate neighborhood. Modification by SR irradiation was found to occur in the entire F-DLC film of about 200 nm thickness. (C) 2018 The Japan Society of Applied Physics

&lt;p&gt;アミノ酸やその前駆体は、炭素質コンドライトのような地球外物質で発見されており、これらは、地球上での最初の生命の誕生に必要な有機物の供給源と考えられている。これらの有機物が地球に運ばれたと考えるならば分子雲、原始太陽系円盤、小惑星、彗星、宇宙塵などの様々な宇宙環境での安定性を考慮する必要がある。本研究ではアミノ酸やアミノ酸前駆体、模擬星間物質に宇宙線を模擬した重粒子線、小惑星中での26Alの放射性崩壊によるγ線を模擬したγ線、原始太陽系円盤での原始太陽からの光を模擬した軟X線を照射し、安定性を評価することを目的とした。今回の実験を通して、複雑態アミノ酸前駆体が最も種々のエネルギーに対して、安定であることが示唆された。また、複雑態アミノ酸前駆体は150 nm ∼ 300 nm 付近に高い吸収があるにもかかわらず、軟X線照射実験で最も安定であった。このことから複雑態アミノ酸前駆体が種々の宇宙環境で安定であることが示唆され

In fast ignition research, a divergence of laser-generated hot electrons is a serious problem. Using diamond like carbon (DLC) cones is one of the realistic solutions to this problem. However, it is difficult to make a stand-alone DLC cone because it needs a thick DLC layer. In this paper, we report survey findings of preparation conditions for a thick DLC layer. DLC layers were prepared by using plasma–based ion implantation and deposition system. Acetylene gas or toluene vapor was used as a source. After trials of many deposition conditions, it is found that low gas pressure and low RF power condition is suitable for a thick DLC deposition. Properties of the made DLC layers were measured by near edge X-ray absorption fine structures (NEXAFS) and elastic recoil detection analysis (ERDA). It is found that these DLC layers have typical hydrogenated amorphous DLC properties. Based on these results, we succeeded in making stand-alone DLC cones.

The irradiation effect on fluorinated diamond-like carbon (F-DLC) film was investigated by measuring the dose dependence of various film properties using synchrotron radiation (SR) in the soft X-rays in the SR dose region from 0 to 2000 mA h. Film flatness was maintained but various film properties and surface properties were found to be changed by the SR irradiation. Wettability of the F-DLC film surface increased dramatically within 20 mA h SR exposure, which was ascribed to the decrease in fluorine on the film surface. Film thickness, film density, composition ratio of fluorine atom in film decreased and sp(2) / (sp(2) + sp(3)) ratio of carbon atoms increased within 300 mA h SR exposure, which were ascribed to the desorption of species containing fluorine atoms. In addition, dominant desorbed species emitted from F-DLC film were found in the fluorocarbon group, CFx. Changes in film properties and film thickness did not proceed, when fluorine content in the F-DLC film decreased to about 10% after the 300 mA h SR exposure.

The classification of diamond-like carbon (DLC) films is imperative in guiding large-scale industrial productions. However, it is not easy to classify this issue based on the structural composition and obtained properties, especially, when the film contains a certain amount of hydrogen. In the present study, two types of hydrogenated DLC films were prepared by electron-cyclotron-resonance chemical-vapor-deposition method with pure C2H2 and Ar gasses with applied negative bias voltages of 0 and 0.5 kV. The structural and surface analyses of these films have shown significant changes of physical and mechanical properties with high reproducibility and low oxygen contents. The comparison of H/C atomic ratio extracted from the combination of Rutherford backscattering and elastic recoil detection analysis and the solid-state nuclear magnetic resonance (NMR) illustrated that the NMR analysis of the present work provides a significant contribution. Therefore, we compared quantitatively the sp(3)/(sp(2) + sp(3)) ratios in the hydrogenated DLC films using the near-edge X-ray absorption fine-structure (NEXAFS) and solid-state NMR methods. The signals of hydrocarbon sp3 ( CH, CH2 and CH3) and a network of sp(3) hybridized carbon (C-sp(3)) can be separated by the solid-state C-13 NMR measurement, from which it is concluded that the former do not enable a detailed interpretation for the internal structural changes of the hydrogenated DLC films with the increase of applied bias voltage. (C) 2016 Elsevier B.V. All rights reserved.

The low-temperature formation of nanocrystalline Si (nc-Si) in SiO<inf>x</inf>film is one of the key technologies in the realization of Si-based photonics and memories. We proposed a low-temperature nc-Si formation method with soft X-ray irradiation. The nc-Si formation depended on the Si/O atomic ratio in the pristine SiO<inf>x</inf>film. The Si-rich regions in SiO<inf>x</inf>films with Si/O ratios higher than 0.67 were crystallized by atomic migration via electron excitation with soft X-ray irradiation at a photon energy near the core level of Si 2p. nc-Si with a mean size of 20 nm was formed by soft X-ray irradiation at a low temperature of 660 °C.

Hydrogenated amorphous silicon carbide films have been fabricated by the decomposition of hexamethyldisilane with a microwave discharge flow of Ar. Mechanically hard films were obtained by applying radio-frequency (RF) bias voltages to the substrate. The atomic compositions of the films were analyzed by a combination of Rutherford backscattering and elastic recoil detection, X-ray photoelectron spectroscopy (XPS), and glow discharge optical emission spectroscopy. The chemical structure was analyzed by carbon-K near-edge X-ray absorption fine structure spectroscopy, high-resolution XPS, and Fourier transform infrared absorption spectroscopy. The structural changes upon the application of RF bias were investigated, and the concentration of O atoms near the film surface was found to play a key role in the mechanical hardness of the present films.

A novel activation method for a B dopant implanted in a Si substrate using a soft X-ray undulator was examined. As the photon energy of the irradiated soft X-ray approached the energy of the core level of Si 2p, the activation ratio increased. The effect of soft X-ray irradiation on B activation was remarkable at temperatures lower than 400°C. The activation energy of B activation by soft X-ray irradiation (0.06 eV) was lower than that of B activation by furnace annealing (0.18 eV). The activation of the B dopant by soft X-ray irradiation occurs at low temperature, although the activation ratio shows small values of 6.2×10-3 at 110°C. The activation by soft X-ray is caused not only by thermal effects, but also electron excitation and atomic movement.

The compositions and bonding states of the amorphous hydrogenated carbon films at various thicknesses were evaluated via near-edge X-ray absorption fine-structure (NEXAFS) and elastic recoil detection analysis combined with Rutherford backscattering spectrometry. The absolute carbon<italic>sp</italic>²contents were determined to decrease to 65% from 73%, while the hydrogen contents increase from 26 to 33 at.% as the film thickness increases. In addition, as the film thickness increases, the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mrow><mml:msup><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow><mml:mo>⁎</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>(C=C),<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M2"><mml:mrow><mml:msup><mml:mrow><mml:mi>σ</mml:mi></mml:mrow><mml:mrow><mml:mo>⁎</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>(C–H),<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M3"><mml:mrow><mml:msup><mml:mrow><mml:mi>σ</mml:mi></mml:mrow><mml:mrow><mml:mo>⁎</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>(C=C), and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M4"><mml:mrow><mml:msup><mml:mrow><mml:mi>σ</mml:mi></mml:mrow><mml:mrow><mml:mo>⁎</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>(C≡C) bonding states were found to increase, whereas the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M5"><mml:mrow><mml:msup><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow><mml:mo>⁎</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>(C≡C) and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M6"><mml:mrow><mml:msup><mml:mrow><mml:mi>σ</mml:mi></mml:mrow><mml:mrow><mml:mo>⁎</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>(C–C) bonding states were observed to decrease in the NEXAFS spectra. Consequently, the film thickness is a key factor to evaluate the composition and bonding state of the films.

The effects of sp(2)-bonded carbon impurities on the electrochemical properties of boron-doped diamond were investigated in moderately ([B]<10(20) cm(-3)) and heavily ([B]>10(21) cm(-3)) boron doping levels. Significant influences of sp(2)-bonded carbon impurities, which show glassy carbon-like electrochemical properties after anodic oxidation, were observed in heavily boron-doped diamond. This indicated that the significant effects of enhanced adsorption properties were possibly caused by surface relaxation of the strains induced by heavy boron doping and sp(2)-bonded carbon impurities. On the other hand, their durability was still similar to diamond electrodes rather than glassy-carbon electrodes because of the low fraction of sp(2)-bonded carbon impurities. Such "active" diamond electrodes are much less suitable for wastewater treatment than ordinary diamond electrodes due to a different oxygen-evolution mechanism. On the other hand, "active" BDD electrodes have a much higher efficiency for electrochemical ozone production than other BDD electrodes. The electrode properties of BDD can be designed by controlling the boron doping level and introducing the sp(2)-bonded carbon impurities. The guidelines proposed in this study can be used effectively to design electrodes according to their individual application, such as for use as electrochemical sensors, in wastewater treatment or electrochemical ozone production. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

To understand the contribution of upbuilding pedogenesis to the accumulation of sulfur (S) in Melanudands, we investigated the vertical distribution of S species using K-edge X-ray absorption near-edge structure (XANES) spectroscopy of S species and vertical variation of 834S values of total Sin two Japanese Melanudands developed above tephra Nt-S, dated at 14-15 cal. ka. These soils have been developed by upbuilding pedogenesis, in which episodic accumulations of volcanic ash and eolian dust transported from the Asian continent are added incrementally to the soil surface while topdown pedogenesis occurs concomitantly forming soil horizons. The oxidation states of S compounds determined by}CANES analysis varied widely in the soil profiles. The predominant S species was highly oxidized S in ester sulfates and inorganic sulfates (+ 6 oxidation state). Proportions of S with reduced and intermediate oxidation states increased episodically to as much as 66%. Ester sulfate-S was found in the soil horizons with estimated ages less than 10 cal ka. A close correlation was found between ester sulfate-S concentrations and Al-associated organic S concentrations (p < 0.05); indeed, the concentrations themselves were roughly similar. The delta S-34 values of total S increased with depth in the two soil profiles. These results suggest that episodic deposits of volcanic ash and eolian dust trapped detritus and humus beneath them during the buildup of the soil surface. The organic S compounds in this material might be decayed as topdown pedogenic processes in the soils. Production of ester sulfate-S may be related to the warm and humid climate of the Holocene, which may have accelerated microbial activity responsible for transformation of reduced to highly oxidized S. Ester sulfate-S might have become Al-associated forms and accumulated in the soils due to their high pedogenic mineral contents. (C) 2014 Elsevier B.V. All rights reserved.

Amorphous silicon germanium (a-Si1-xGex)films were crystallized by irradiation with soft X-rays of various photon energies. The crystallization upon soft X-ray irradiation is related to Ge concentration, photon energy, and photon flux density. The Ge atom was the trigger for the crystallization of the SiGe film because the atomic migration of Ge atoms was enhanced by electron excitation during soft X-ray irradiation, compared with Si atoms. As the photon energy decreased from 130 to 50 eV, the crystalline fraction increased. In the Si0.5Ge0.5 film, the ratio of peaks attributable to the crystal phases to those attributable to the amorphous phases of Si-Si, Si-Ge, and Ge-Ge bonds changed with irradiated photon energy. This is explained by the relationship between the orbital energies of Si 2p and Ge 3d and the photon energy of irradiated soft X-rays, because the electron excitation probability was determined by this relationship. Therefore, it is considered that soft X-ray irradiation crystallization occurred via the exitation of electrons from the core level. (C) 2014 The Japan Society of Applied Physics

A novel activation method of B dopant in Si wafer using soft X-ray undulator was proposed. As the photon energy of soft X-ray approached the energy of core level of Si 2p, the activation ratio was increased. The effect of soft X-ray irradiation on activation was remarkable below 500°C. The activation energy for the soft X-ray irradiation (0.06 eV) was lower than that for a thermal annealing (0.18 eV). By using B10H14 cluster as B source, the sheet resistance of 55 Ω/sq was obtained at 490 °C.

A wide variety of organic compounds have been found in space, and their relevance to the origin of life is discussed. Interplanetary dust particles (IDPs) are most promising carriers of extraterrestrial organic compounds, but presence of bioorganic compounds are controversial since they are so small and were collected in the terrestrial biosphere. In addition, IDPs are directly exposed to cosmic and solar radiation. Thus, it is important to evaluate the stability of organics in IDPs in space environment. We are planning a novel astrobiology mission named Tanpopo by utilizing the Exposed Facility of Japan Experimental Module (JEM/EF) of the International Space Station (ISS). Two types of experiments will be done: Capture experiments and exposure experiments. In the exposure experiments, organics and microbes will be exposed to the space environments to examine possible alteration of organic compounds and survivability of microbes. Selected targets for the exposure experiments of organic compounds are as follows: Amino acids (glycine and isovaline), their possible precursors (hydantoin and 5-ethyl-5-methyl hydantoin) and complex precursors "CAW" synthesized from a mixture of carbon monoxide, ammonia and water by proton irradiation. In addition to them, powder of the Murchison meteorite will be exposed to examine possible alteration of meteoritic organics in space. We will show the results of preparatory experiments on ground by using a UV lamp, a ⁶⁰Co source, synchrotron facilities, and a heavy ion irradiation facility.