| Yukihiko Yamagata | Last modified date：2024.04.26 |
Associate Professor /
Electrical Process Engineering /
Department of Advanced Energy Science and Engineering /
Faculty of Engineering Sciences
Papers
| 1. | Daisuke Nakamura, Yiming Pan, Kentaro Tomita, Yukihiro Yamagata, Kazunori Koga, Hakaru Mizoguchi, Masaharu Shiratani, Towards the Development of High-Power EUV Light Source Based on Observation of Laser-Produced Sn Plasma Dynamics, Proceedings of the 13th Advanced Lasers and Photon Sources Conference (PACIFICO Yokohama, Japan, April 22-26, 2024), 2024.04. |
| 2. | Hakaru Mizoguchi, Kentaro Tomita, Daisuke Nakamura, Kuichiro Kouge, Yukihiro Yamagata, Yiming Pan, Atsushi Sunahara, Takeshi Higashiguchi, Katsunobu Nishihara, Toru Ogawa, Takashi Tanaka, Masaharu Shiratani, Plasma Dynamics and Future of LPP-EUV Source for Semiconductor Manufacturing (S2), Proceedings of the 8th EUV-FEL Workshop (Akihabara, Janap, Jan. 29, 2024), Keynote, 2024.01. |
| 3. | Hakaru Mizoguchi, Kentaro Tomita, Daisuke Nakamura, Yukihiro Yamagata, Takeshi Higashiguchi, Atsushi Sunahara, Katsunobu Nishihara, Masaharu Shiratani, Plasma Dynamics and Future of LPP-EUV Source for Semiconductor Manufacturing, Proceedings of the 2023 Source Workshop (Aachen, Germany, October 21-25, 2023), Keynote, 2023.10. |
| 4. | Hakaru Mizoguchi, Kentaro Tomita, Daisuke Nakamura, Kouichiro Kouge, Yukihiro Yamagata, Yiming Pan, Atsushi Sunahara, Takeshi Higashiguchi, Katsunobu Nishihara, Toru Ogawa, Takashi Tanaka, Masaharu Shiratani, Plasma Dynamics and Future of LPP-EUV Source for Semiconductor Manufacturing, Proceedings of the 20th International Symposium on Laser-Aided Plasma Diagnostics (Kyoto, Japan, Sept. 10–14, 2023), G8, 2023.09. |
| 5. | Katsunori Muraoka, Yukihiko Yamagata, Rikiya Abe, Necessity of a nationally coherent energy strategy for meeting the Paris Agreement: a case study for Japan, The European Physical Journal, 10.1140/epjp/s13360-023-04206-8, 136, 587, 1-9, 2023.06.  |
| 6. | Hakaru Mizoguchi, Kentaro Tomita, Daisuke Nakamura, Kouichiro Kouge, Yukihiro Yamagata, Yiming Pan, Atsushi Sunahara, Takeshi Higashiguchi, Katsunobu Nishihara, Toru Ogawa, Takashi Tanaka, Masaharu Shiratani, Plasma Dynamics and Future of LPP-EUV Source for Semiconductor Manufacturing, Proceedings of the 2023 EUVL Workshop & Supplier Showcase (imec ▪ Leuven, Belgium, June 3-7, 2023), G8, 2023.06. |
| 7. | Yiming Pan, Kentaro Tomita, Yukihiko Yamagata, Atsushi Sunahara, Katsunobu Nishihara, Investigation of dynamics of laser-produced carbon plasma during the laser irradiation using collective Thomson scattering, Journal of Physics D: Applied Physics, 10.1088/1361-6463/aca6f5, 56, 2, 025201-1-025201-15, 2022.12. |
| 8. | Katsunori Muraoka, Yukihiko Yamagata, Rikiya Abe, Importance of Increasing Wind Energy for a Large-scale Introduction of Variable Renewable Energies into Japan Based on Their Characteristics, Journal of the Japan Institute of Energy, 10.3775/jie.101.16., 101, 1, 16-23, 2022.01. |
| 9. | Yukihiko Yamagata, Ryo Iwasaka, Keita Shigyo, Juntaro Tanaka, Yasuyuki Kawaguchi, Katsunori Muraoka, Simple Optical Measurements of Pre-treated Surface Roughness for Thermal Spray, Journal of Engineering Research and Reports, 10.9734/JERR/2020/v13i217095, 13, 2, 1-10, 2020.06. |
| 10. | Yukihiko Yamagata, Ryo Iwasaka, Yasuyuki Kawaguchi, Masafumi Yamasaki, Katsunori Muraoka, Spectroscopic observation of radiation emitted from thermally-produced spray droplets and the resulting temperature determination, Japanese Journal of Applied Physics, 10.7567/JJAP.57.126102, 57, 126102, 1-4, 2018.11. |
| 11. | Yasuyuki Kawaguchi, Masaharu Shiratani, Yukihiko Yamagata, Katsunori Muraoka, Simultaneous measurement system of temperature and velocity for thermal plasma spray droplets, Proceedings of Asia-Pacific Conference on Plasma Physics (Nov. 12-17, 2018, Kanazawa, Japan), 1-4, 2018.11. |
| 12. | M. Horiuchi, K. Miura, T. Shimada, Y. Manabe, Y. Yamagata, Comparative study of temperature measurement in a blue-LED package by using pulsed-laser Raman scattering and thermocouple method, Proceedings of the 16th International Symposium on the Science and Technology of Lighting (June 17th‐22th, 2018, Sheffield University, Sheffield,UK) Th4.4.10 (2 pages), 2018., Th4.4.10, 1-2, 2018.06. |
| 13. | Y. Kawaguchi, N. Kobayashi, Yukihiko Yamagata, F. Miyazaki, M. Yamasaki, J. Tanaka, K. Muraoka, Optical monitoring systems for thermal spray processes Droplets behavior and substrate pre-treatments, Journal of Instrumentation, 10.1088/1748-0221/12/11/C11031, 12, 11, 2017.11, Thermal spray is a technique to form molten droplets using either plasma- or combustion-heating, which impinge upon substrates to form coating layers for various purposes, such as anti-corrosion and anti-wear layers. Although it is an established technique having a history of more than a century, operations of spray guns together with preparing suitable substrate surfaces for obtaining good coating layers still rely on experienced technicians. Because of the necessity of meeting more and more stringent requirements for coating quality and cost from customers, there has been a strong need to try to monitor spray processes, so as to obtain the best possible spray coating layers. The basic requirements for such monitoring systems are ∗reasonably cheap, ∗easy operation for laypersons, ∗easy access to targets to be investigated, and ∗an in-situ capability. The purpose of the present work is to provide suitable optical monitoring systems for (1) droplets behavior and (2) substrate pre-treatments. For the former (1), the first result was already presented at the 17th laser-aided plasma diagnostics meeting (LAPD17) in 2015 in Sapporo, and the results of its subsequent applications into real spray environments are shown in this article in order to validate the previous proposal. Topic (2) is new in the research program, and the proof-of-principle experiment for the proposed method yielded a favorable result. Based on this positive result, an overall strategy is being planned to fulfill the final objective of the optical monitoring of substrate pre-treatments. Details of these two programs (1) and (2) together with the present status are described.. |
| 14. | M. Horiuchi, Y. Yamagata, S. Tsutsumi, K. Tomita, Y. Manabe, The Development of a System for Measuring the Junction Temperatures of Multiple LEDs on a Package Simultaneously by Using Pulsed-laser Raman Scattering, Journal of Science and Technology in Lighting, 10.2150/jstl.IEIJ160000584, 41, 101-107, Online ISSN : 2432-3233 Print ISSN : 2432-3225, 2017.11, This paper details a novel method consisting of employing a pulsed-laser Raman scattering technique to estimate junction temperatures of several LED chips arranged in a straight line on a phosphor-less blue-LED package and a phosphor-resin coated blue-LED package. By using a sheet-shaped irradiation pattern, each of the GaN-E2H Raman spectra from several chips mounted straight on a phosphor-less blue LED package was observed at the same time and the junction temperature of each chip was estimated successfully by means of each Raman shift during operation despite the existence of strong LED emission. In addition, the GaN-E2H Raman signal from the phosphor-resin coated blue-LED was observed for the first time by using 633 nm laser to reduce the negative influence from the phosphor and light diffusing substances in the resin. It is concluded that this technique would be a useful method for a remote and standard system for 2D mapping of the junction temperatures of blue-LED packages.. |
| 15. | Y. Kawaguchi, N. Kobayashi, Yukihiko Yamagata, F. Miyazaki, M. Yamasaki, K. Muraoka, Spatially-resolved velocities of thermally-produced spray droplets using a velocity-divided Abel inversion of photographed streaks, Journal Physics D: Applied Physics, 10.1088/1361-6463/aa87e0, 50, 42, 2017.09, Droplet velocities of thermal spray are known to have profound effects on important coating qualities, such as adhesive strength, porosity, and hardness, for various applications. For obtaining the droplet velocities, therefore, the TOF (time-of-flight) technique has been widely used, which relies on observations of emitted radiation from the droplets, where all droplets along the line-of-sight contribute to signals. Because droplets at and near the flow axis mostly contribute coating layers, it has been hoped to get spatially resolved velocities. For this purpose, a velocity-divided Abel inversion was devised from CMOS photographic data. From this result, it has turned out that the central velocity is about 25% higher than that obtained from the TOF technique for the case studied (at the position 150 mm downstream of the plasma spray gun, where substrates for spray coatings are usually placed). Further implications of the obtained results are discussed.. |
| 16. | Yusufumi Kawaguchi, Fumihiro Miyazaki, Masafumi Yamasaki, 山形 幸彦, Katsunori Muraoka, 小林 希, Correlations of coating qualities deposited using three different thermal spray technologies with measured temperatures and velocities of spray droplets ejected from their guns, Coatings, 10.3390/coatings7020027, 7, 2, 1-10, 2017.02. |
| 17. | Makoto Horiuchi, Shin-ichi Tsutsumi, 富田 健太郎, Yoshio Manabe, 山形 幸彦, Development of simultaneous measurement system of junction temperatures in a LED module using pulsed-laser Raman scattering, Proceedings of the 15th International Symposium on the Science and Technology of Lighting (May 22nd‐27th, 2016, Kyoto University, Kyoto, Japan), CP39, 1-2, 2016.05. |
| 18. | Shin-ichi Tsutsumi, Makoto Horiuchi, 富田 健太郎, Yoshio Manabe, 山形 幸彦, Influence of phosphor on junction-temperature measurement of white-LED using pulsed-laser Raman scattering, Proceedings of the 15th International Symposium on the Science and Technology of Lighting (May 22nd‐27th, 2016, Kyoto University, Kyoto, Japan), CP40, 1-2, 2016.05. |
| 19. | Katsunori Muraoka, Friedrich Wagner, 山形 幸彦, A.J.H. Donné, Short- and long-range energy strategies for Japan and the world after the Fukushima nuclear accident, JOURNAL OF INSTRUMENTATION, 10.1088/1748-0221/11/01/C01082, 11, 2016.01. |
| 20. | K. Muraoka, F. Wagner, Yukihiko Yamagata, A. J.H. Donné, Short- and long-range energy strategies for Japan and the world after the Fukushima nuclear accident, Journal of Instrumentation, 10.1088/1748-0221/11/01/C01082, 11, 1, 2016.01, The accident at the Fukushima Dai-ichi nuclear power station in 2011 has caused profound effects on energy policies in Japan and worldwide. This is particularly because it occurred at the time of the growing awareness of global warming forcing measures towards decarbonised energy production, namely the use of fossil fuels has to be drastically reduced from the present level of more than 80% by 2050. A dilemma has now emerged because nuclear power, a CO2-free technology with proven large-scale energy production capability, lost confidence in many societies, especially in Japan and Germany. As a consequence, there is a world-wide effort now to expand renewable energies (REs), specifically photo-voltaic (PV) and wind power. However, the authors conjecture that PV and wind power can provide only up to a 40% share of the electricity production as long as sufficient storage is not available. Beyond this level, the technological (high grid power) and economic problems (large surplus production) grow. This is the result of the analysis of the growing use of REs in the electricity systems for Germany and Japan. The key element to overcome this situation is to develop suitable energy storage technologies. This is particularly necessary when electricity will become the main energy source because also transportation, process heat and heating, will be supplied by it. Facing the difficulty in replacing all fossil fuels in all countries with different technology standards, a rapid development of carbon capture and storage (CCS) might also be necessary. Therefore, for the short-range strategy up to 2050, all meaningful options have to be developed. For the long-range strategy beyond 2050, new energy sources (such as thermonuclear fusion, solar fuels and nuclear power - if inherently safe concepts will gain credibility of societies again), and large-scale energy storage systems based on novel concepts (such as large-capacity batteries and hydrogen) is required. It is acknowledged that the prediction of the future is difficult; therefore, the only insurance in this situation is by intensified research into all viable options.. |
| 21. | Yusufumi Kawaguchi, Fumihiro Miyazaki, Masafumi Yamasaki, 山形 幸彦, Katsunori Muraoka, The first result of an optical monitoring system for optimization of thermal spray droplets, JOURNAL OF INSTRUMENTATION, 10.1088/1748-0221/10/12/C12011, 10, 2015.12. |
| 22. | Y. Kawaguchi, F. Miyazaki, M. Yamasaki, Yukihiko Yamagata, K. Muraoka, The first result of an optical monitoring system for optimization of thermal spray droplets, Journal of Instrumentation, 10.1088/1748-0221/10/12/C12011, 10, 12, 2015.12, This article describes the first experimental result of a simple but reliable optical monitoring system for optimization of thermal spray droplets. The system, which was used in the present experiment and the authors call as ''a pre-proto instrument'', consisted of a light collecting lens followed by a part for separating the light into two wavelengths, with the light of each wavelength guided into an avalanche photo-diode (APD) to be electronically detected. First, it was calibrated using a special purpose-built calibration system. Then, it was taken to a plasma spray gun for a field test, yielding a satisfactory first result. Based on this positive result, future plans of the project are discussed.. |
| 23. | Makoto Horiuchi, 山形 幸彦, Shin-ichi Tsutsumi, 富田 健太郎, Yoshio Manabe, Development of junction temperature estimation system for light-emitting LED using pulsed-laser Raman scattering, Journal of Solid State Lighting, 10.1186/s40539-015-0026-9, Vol. 2, 7, 1-7, 2015.07, [URL], A new method by using a pulsed-laser Raman scattering technique was employed to estimate junction temperature of a fluorescence-resin-less blue-LED package. Temperature dependent Raman shift of E2 H mode of GaN layer in the blue-LED were obtained and were in good agreement with the experimental data published by the other researchers. This technique was applied to estimation of a junction temperature of the light-emitting blue-LED. The junction temperature was successfully estimated even under the strong stray light and LED light emission. It is considered that the proposed technique would be a remote and standard system for measuring the junction temperature of light-emitting white-LEDs. |
| 24. | 山形 幸彦, Ryota Takakura, kensyo Nakagawa, Yoshinobu Kawai, 内野 喜一郎, Spatial control of very high frequency plasma generation for large scale plasma applications, Proceedings of the XXXII International Conference on Phenomena in Ionized Gases ( 26th – 31st July 2015, Iași, Romania), 54, 016101, P4.12 (4 pages), 2015.07. |
| 25. | Daisuke Kuwahara, Yuriko Tanida, Masaki Watanabe, 山形 幸彦, Shunjiro Shinohara, Naoto Teshigahara, Development of Ar I and Ar II Measuring System Using Laser-Induced Fluorescence Methods in High-Density Helicon Plasma, Plasma and Fusion Research: Regular Articles, Vol. 10, 3401057 (4 pages), 2015.05. |
| 26. | Nima Bolouki, KENTARO TOMITA, Safwat Hassaballa, 山形 幸彦, 内野 喜一郎, Temporal evolution of electron density and electron temperature profiles in a non-thermal atmospheric-pressure plasma measured by laser Thomson scattering, Jpn. J. Appl. Phys. , 54, 016101, (4 pages), 2015.01. |
| 27. | Nima Bolouki, Kentaro Tomita, Safwat Hassaballa, Yukihiko Yamagata, Kiichiro Uchino, Temporal evolution of electron density and electron temperature profiles in a non-thermal atmospheric-pressure plasma measured by laser Thomson scattering, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.7567/JJAP.54.016101, 54, 1, 2015.01, The laser Thomson scattering technique has been applied for measuring the spatiotemporal changes in the electron density (ne) and electron temperature (Te) of a capacity-coupled micro-discharge generated in neon gas at near-atmospheric pressure. A significant difference has been observed in temporal behavior between ne and Te after the discharge generation. The value of ne decreases monotonically from t = 25 ns when the electrical input is truncated. On the other hand, Te is approximately 1.7 eV at 15 ns and, after this point, Te rapidly decreases to about 0.8 eV. Subsequently, Te decreases gradually. These features are discussed on the basis of the recombination processes.. |
| 28. | Kensho Nakagawa, Ryuta Takakura, 山形 幸彦, 内野 喜一郎, Yoshinobu Kawai, Control of VHF plasma generation area for large scale plasma applications, the 16th Cross Straits Symposium on Energy and Environmental Science and Technology (Pusan National Univ., Pusan, Korea, 2014.11.13-15), 1, 1-2, 2014.11. |
| 29. | 山形 幸彦, Makoto Horiuchi, 富田 健太郎, Yoshio Manabe, Development of temperature measurement system for LED junction using pulsed-laser Raman scattering, Proceedings of the 14th International Symposium on Science and Technology of Lighting (Spazio Como, Como Lake, Italy, Jun. 22-27, 2014) , 1, 245-248, 2014.06. |
| 30. | Naoto Teshigahara, Shunjiro Shinohara, 山形 幸彦, Daisuke Kuwahara, Masaki Watanabe, Development of 2D Laser-Induced Fluorescence (LIF) System in High-Density Helicon Plasma, Plasma and Fusion Research: Regular Articles, Vol. 9, 3406055 (4 pages), 2014.05. |
| 31. | 富田 健太郎, Nima Bolouki, Kazutaka Nishikawa, Kazuhiko Nagai, 山形 幸彦, 内野 喜一郎, Diagnostics of Atmospheric Pressure Plasmas Using Laser Thomson Scattering, Proceedings of the 8th International Conference on Reactive Plasmas and 31st Symposium on Plasma Processing (Fukuoka Convention Center, Fukuoka, Japan, Feb. 3-7, 2014), 6p-PM-S09-P21, (4 pages), 2014.02. |
| 32. | Naoto Teshigahara, Shunjiro Shinohara, Yukihiko Yamagata, Daisuke Kuwahara, Masaki Watanabe, Development of 2D Laser-Induced Fluorescence (LIF) system in high-density helicon plasma, Plasma and Fusion Research, 10.1585/pfr.9.3406055, 9, SpecialIssue2, 2014.01, Lifetimes of most electric propulsion devices are limited owing to electrode erosion and contamination by plasmas. To overcome this problem, a Helicon Electrodeless Advanced Thruster (HEAT) was proposed by our research team. This scheme employs a high-density (~ 1013 cm-3) helicon plasma accelerated by the Lorentz force, which is produced by various acceleration methods. For feasibility of this method, a Laser-Induced Fluorescence (LIF) system was developed. The LIF is a powerful tool for plasma diagnostics because it is a non-invasive method that allows high spatial resolution. Using the LIF, it is possible to deduce velocity distribution functions of different particles (ions, atoms, and molecules). In this paper, we report the details of our novel 2D LIF system as well as some preliminary experimental results. Argon ion velocity distributions at different axial and radial locations were obtained using the novel 2D system. Ion velocity was greatest (~ 2.8 km/s) at z = -24 cm among all the points measured along the z-axis. Velocity values were approximately 2.7 and 3.2 km/s for radial positions of r = 0 and 3 cm, respectively. Ion temperature values were approximately 0.56 and 0.61 eV at r = 0 and 3 cm, respectively.. |
| 33. | Kentaro Tomita, Kazuhiko Nagai, Takahiro Shimizu, Nima Bolouki, Yukihiko Yamagata, Kiichiro Uchino, Toshiro Kaneko, Thomson scattering diagnostics of atmospheric plasmas in contact with ionic liquids, Applied Physics Express, 10.7567/APEX.7.066101, 7, 6, 2014.01, Laser Thomson scattering has been applied to a nonequilibrium atmospheric plasma in contact with an ionic liquid to measure both electron density (n e) and electron temperature (Te). The discharge plasma was produced between a needle and a plane ionic-liquid electrode separated by a 3mm gap. In comparison with a conventional metal electrode, distinct differences were found in spatial profiles of ne and Te of the plasma produced with the ionic-liquid electrode.. |
| 34. | Naoto Teshigahara, Shunjiro Shinohara, 山形 幸彦, Daisuke Kuwahara, Masaki Watanabe, Development of 2D Laser Induced Fluorescence (LIF) system in High-Density Helicon Plasma, Proceedings of the 23rd International Toki Conference (Ceratopia Toki, Gifu, Japan, November 18~21, 2013), P2-59, 2013.11. |
| 35. | 富田 健太郎, 山形 幸彦, 内野 喜一郎, Thomson Scattering Diagnostics of Atmospheric Pressure Plasmas Generated with Ionic Liquid Electrode, The 6th International Conference on Plasma Nano Technology and Science (2013.2.2-3, Gifu, Japan), S-2, 2013.02. |
| 36. | 富田 健太郎, Nima Bolouki, Kentaro Nagata, 山形 幸彦, 内野 喜一郎, Thomson Scattering Diagnostics of Pulsed Filament Discharges Produced at Near-Atmospheric Pressure, 5th International Symposium on Advanced Plasma Science and Its Applications for Nitrides and Nanomaterials (ISPlasma 2013) (2013.1.28-2.1, Nagoya, Japan), P1025A, 2013.01. |
| 37. | Nima Bolouki, 富田 健太郎, 山形 幸彦, 内野 喜一郎, Laser Thomson scattering diagnostics of pulsed filamentary discharge, 65th Gaseous Electronics Conference, 57, 8, 18-18, 2012.11. |
| 38. | 富田 健太郎, Nima Bolouki, Kentaro Nagata, 山形 幸彦, 内野 喜一郎, Studies of Pulsed Discharge Plasmas Produced at Atmospheric Pressure using Laser Thomson Scattering, International Union of Material Research Societies - International Conference on Electronic Materials 2012(IUMRS-ICEM 2012), (2012.9.23-28, Yokohama, Japan), D-4-O24-007, D-4-O24-007, 2012.09. |
| 39. | 山形 幸彦, Makoto Kai, Koutaro Miyashita, Kazuki Kamio, Yoshio Manabe, Experimental and Numerical approach to a design of highly efficient and long-lived fluorescent lamp, 13th International Symposium on the Science and Technology of Lighting, (Troy, NY, USA, June 24-29, 2012) , 83-84, 2012.06. |
| 40. | Kentaro Tomita, Nima Bolouki, Hiroki Shirozono, Yukihiko Yamagata, Kiichiro Uchino, Koichi Takaki, Two-dimensional Thomson Scattering Diagnostics of Pulsed Discharges Produced at Atmospheric Pressure, Journal of Instrumentation, 7, C02057 (11pages), 2012.02. |
| 41. | Kentaro Tomita, N. Bolouki, H. Shirozono, Yukihiko Yamagata, Kiichiro Uchino, K. Takaki, Two-dimensional Thomson scattering diagnostics of pulsed discharges produced at atmospheric pressure, Journal of Instrumentation, 10.1088/1748-0221/7/02/C02057, 7, 2, 2012.02, Laser Thomson scattering (LTS) method has been applied to measure two dimensional distributions of electron density (ne) and electron temperature (Te) of a pulsed discharge in Ne gas at a pressure of 400 Torr. Such a discharge was produced with good reproducibility by using a set of electrodes composed of a needle and a hemisphere with a spacing gap of 0.5 mm. The values of ne and Te at t = 25 ns after the start of the discharge and at the center of the discharge were evaluated to be 4.6 × 1022 m-3 and 1.0 eV, respectively. Based on the observed signal intensity and noise components, signal-to-noise ratios were examined and the way to apply present diagnostic system to the discharge plasma with an electron density as low as 1018 m-3 was discussed.. |
| 42. | Nima Bolouki, 富田 健太郎, 山形 幸彦, 内野 喜一郎, Diagnostics of Dielectric Barrier Microdischarges Using Laser Thomson Scattering, 64th Gaseous Electronics Conference, 56, 15, 11-11, 2011.11. |
| 43. | 山形 幸彦, K. Inoue, H. Okano, Removable of environmental hazardous materials by dielectric barrier discharge in closed reaction space - applications for volatile organic compounds, diesel particulate matters and nitric oxide, The 16th International Conference on Advanced Oxidation Technologies for Treatment of Water, Air and Soil (7-10 November, 2011, The Town & Country Resort of San Diego, California, USA), IL-63, 2011.11. |
| 44. | 富田 健太郎, Nima Bolouki, 山形 幸彦, 内野 喜一郎, Thomson scattering diagnostics of a pulsed discharge produced at around atmospheric pressure, , 15th International Symposium on Laser-Aided Plasma Diagnostics, 2011.10. |
| 45. | Koji Inoue, Hiroshi Okano, Yukihiko Yamagata, Katsunori Muraoka, Yasutake Teraoka, Performance tests of newly developed adsorption/plasma combined system for decomposition of volatile organic compounds under continuous flow condition, Journal of Environmental Sciences, Vol. 23, No.1, pp.139-144, 2011.01. |
| 46. | Koji Inoue, Hiroshi Okano, Yukihiko Yamagata, Katsunori Muraoka, Yasutake Teraoka, Performance tests of newly developed adsorption/plasma combined system for decomposition of volatile organic compounds under continuous flow condition, Journal of Environmental Sciences, 10.1016/S1001-0742(10)60385-3, 23, 1, 139-144, 2011.01, The adsorption/plasma decomposition with the combination of adsorption honeycomb-sheets and a plasma element is a new technology for small-sized apparatuses to decompose volatile organic compounds (VOCs) at concentrations lower than about 100 ppm. The feasibility of the prototype adsorption/plasma decomposition apparatus was evaluated with the simulated exhausts containing one VOC component and with real exhausts from a painting booth and an adhesion factory. The apparatus decomposed VOCs effectively at the painting booth exhaust but not always satisfactorily at the adhesion factory exhaust. The performance test results with real exhausts were discussed with respect to the concentration and discharge pattern of the exhausts and the basic properties of the system such as cooperation of adsorption and plasma reaction and the concentration dependence of the performance.. |
| 47. | Kazuki Kamio, Syo Naitou, Yukihiko Yamagata, Kiichiro Uchino, Kentaro Tomita, Makoto Kai, Yoshio Manabe, Effect of ambient gas on electrode temperature and emitter material emission in a low-pressure fluorescent lamp, Proceedings of the 12th Cross Straits Symposium (Pohang University of Science and Technology (POSTECH), Pohang, Korea, November 17-18, 2010), MSP10, pp. 65-66, 2010.07. |
| 48. | I. Kobayashi, R. Bruckshaw, M. Kai, Y. Manabe, Y. Yamagata, R. Devonshire, Modeling of Emitter Loss in Fluorescent Lamps, Proceedings of the 12th International Symposium on the Science and Technology of Light Sources ( Eindhoven, the Netherlands, July 11-16, 2010), pp. 211-212, 2010.07. |
| 49. | Y. Yamagata, M. Kai, S. Naito, K. Kamio, Y. Manabe, K. Uchino, Gas dependency of electrode temperature and emission of emitter material in a low-pressure fluorescent lamp, Proceedings of the 12th International Symposium on the Science and Technology of Light Sources ( Eindhoven, the Netherlands, July 11-16, 2010), pp. 527-528, 2010.07. |
| 50. | Yukihiko Yamagata, Makoto Kai, Sho Naito, Kentaro Tomita, Kiichiro Uchino, Yoshio Manabe, Relationship between Ba atom emission and electrode temperature in a low-pressure fluorescent lamp, Thin Solid Films, 10.1016/j.tsf.2009.11.041, 518, 13, 3449-3452, 2010.04, A relationship between emission characteristics of Ba atom as an emitter material and temperature distributions of an electrode in a fluorescent lamp is described, which is measured by using laser-induced fluorescence and black-body radiation method, respectively. In a virgin lamp, a hot spot observed at the electrode edge connected to the power supply is the main source of Ba atom emission. In a long-term-used lamp, it is shown that Ba atom emission, thermionic electron emission in cathode half-cycle and electron collection in anode half-cycle are most active on the hot spot appearing on the center of the electrode.. |
| 51. | Yukihiko Yamagata, Makoto Kai, Sho Naito, Kentaro Tomita, Kiichiro Uchino, Yoshio Manabe, Relationship between Ba atom emission and electrode temperature in a low-pressure fluorescent lamp, Thin Solid Films, Vol. 518, pp. 3449-3452, 2010, 2010.02. |
| 52. | Yukihiko Yamagata, Sho Naito, Makoto Kai, Kentaro Tomita, Kiichiro Uchino, Yoshio Manabe, Relationship between distribution of electrode temperature and emission characteristics of emitter material in low-pressure fluorescence lamp, Proceedings of the 27th Symposium on Plasma Processing, pp.73-74 (2010), 2010.02. |
| 53. | Hiroki Shirozono, Bolouki Nima, Kentaro Tomita, Yukihiko Yamagata, Kiichiro Uchino, Measurements of electron density and electron temperature of pulsed filament discharges produced in near-atmospheric pressure, Proceedings of the 27th Symposium on Plasma Processing, pp.123-124 (2010), 2010.02. |
| 54. | Yosuke Fujii, Shintaro Tanaka, Yukihiko Yamagata, Decomposition of electrostatic-precipitated diesel particulate matters withnitric oxide by dielectric barrier discharge in closed cycle, Proceedings of the 11th Cross Straits Symposium on Materials, Energy, and Environmental Sciences, ETP-02, pp. 311-312 (2009), 2009.11. |
| 55. | Yukihiko Yamagata, Yosuke Fujii, Yozo Kawagashira, Katsunori Muraoka, Decompositions of diesel particulate materials and nitric oxides using dielectric barrier discharge in closed reaction space, Proceedings of the 15th International Conference on Advanced Oxidation Technologies for Treatment of Water, Air and Soil, p.75 (2009), 2009.10. |
| 56. | Kentaro Tomita, Yukihiko Yamagata, Kiichiro Uchino, Development of a Laser Thomson Scattering System for Pulsed Filament Discharges Produced in Near-Atmospheric Pressure, Proceedings of the 31st International Symposium on Dry Process, pp.165-166 (2009), 2009.09. |
| 57. | Masaru Naka, Yuichi Egashira, Kentaro Tomita, Yukihiko Yamagata, Kiichiro Uchino, Y. Manabe, T. Ueda, MEASUREMENTS OF DISTRIBUTIONS OF Ba ATOM DENSITY AND ELECTRODE TEMPERATURE IN LOW-PRESSURE FLUORESCENT LAMP, Journal of Plasma and Fusion Research SERIES, Vol.8, pp.1308-1312 (2009), 2009.09. |
| 58. | Yasushi SONODA, Shuhei NISHIMOTO, Kentaro TOMITA, Safwat HASSABALLA, Yukihiko YAMAGATA, Kiichiro UCHINO, Laser Thomson Scattering Diagnostics of Dielectric Barrier Discharge Plasmas, Journal of Plasma and Fusion Research SERIES, Vol.8, pp.696-699 (2009), 2009.09. |
| 59. | Kiichiro Uchino, Kentaro Tomita, Yukihiko Yamagata, Diagnostics of a pulsed filament discharge using laser Thomson scattering, Proceedings of the 19th International Symposium on Plasma Chemistry, P.2.2.26, pp.1-4 (2009), 2009.07. |
| 60. | Yukihiko Yamagata, Makoto Kai, Susumu Naito, Masaru Naka, Kentaro Tomita, Kiichiro Uchino, Yoshio Manabe, Ba atom emission and electrode temperature distribution in a low-pressure fluorescent lamp, Proceedings of the 19th International Symposium on Plasma Chemistry, P.2.2.28, pp.1-4 (2009), 2009.07. |
| 61. | Koji Inoue, Keimei Furuki, Hxiroshi Okano, Yukihiko Yamagata, Katsunori Muraoka, A new decomposition system for volatile organic compounds using combinations of dielectric barrier discharges with zeolite honeycomb sheets, Electrical Engineering in Japan (English translation of Denki Gakkai Ronbunshi), 10.1002/eej.20736, 168, 1, 1-10, 2009.07, A new decomposition system for volatile organic compounds (VOCs), based on dielectric barrier discharges combined with zeolite honeycomb sheets, has been developed. A discharge element was made of layered flat metal sheets covered with mica sheets separated by 2 mm, in which corrugated (honeycomb-shaped) ceramic sheets embedded with zeolites were inserted. This element was shown to satisfy the requirements of durability and flexibility to meet various sizes. Barrier discharges were investigated using this discharge element over wide ranges of operating conditions, in terms of the power consumption and decompositions of various types of VOCs. By selecting suitable operating scenarios, it was found that decomposition of more than 90% of most VOCs was possible, at reasonable power consumption and without electrode contamination by decomposition products. Finally, areas of competitive applications of the present system versus existing decomposition systems are also dicussed.. |
| 62. | Y. Yamagata, Y. Fujii, Y. Kawagashira, K. Muraoka, Decomposition of electrostatic-precipitated particulate materials from diesel exhaust gas with nitric oxides using dielectric barrier discharge, Electrical Review, Vol. 85, pp. 124-127, 2009.05. |
| 63. | Yukihiko Yamagata, Sho Naito, Makoto Kai, Kentaro Tomita, Kiichiro Uchino, Yoshio Manabe, Relationship between distribution of electrode temperature and emission characteristics of emitter material in low-pressure fluorescence lamp, Proceedings of Plasma Science Symposium 2009 and the 26th Plasma Processing Symposium, pp.73-74 (2009), 2009.02. |
| 64. | Yukihiko Yamagata, Masaru Naka, Hirohumi Shinozaki, Kentaro Tomita, Kiidhiro Uchino, Makoto Kai, Yoshio Manabe, Electrode temperature distribution and Ba atom emission in a low-pressure fluorescent lamp, Proceedings of Plasma Science Symposium 2009 and the 26th Plasma Processing Symposium, pp.310-311 (2009), 2009.02. |
| 65. | Yosuke Fujii, Shintaro Tanaka, Yukihiko Yamagata, Katsunori Muraoka, Simultaneous decompositions of diesel particulate materials and nitric oxides using dielectric barrier discharge in closed cycle, Proceedings of Plasma Science Symposium 2009 and the 26th Plasma Processing Symposium, pp.70-71 (2009), 2009.02. |
| 66. | Y. Yamagata, M. Naka, H. Shinozaki, K. Tomita, K. Uchino, M. Kai, Y. Manabe, Electrode temperature distribution and Ba atom emission in a low-pressure fluorescent lamp, Proceedings of Plasma Science Symposium 2009 and the 26th Plasma Processing Symposium (Nagoya, Japan, February 2-4, 2009), pp. 310-311, 2009.02. |
| 67. | Y. Yamagata, S. Nishimoto, H. Ooga, S. Hassaballa, K. Tomita, K. Uchino, Measurements of electron temperature and density of pulse filament discharge using laser Thomson scattering technique, Proceedings of Plasma Science Symposium 2009 and the 26th Plasma Processing Symposium (Nagoya, Japan, February 2-4, 2009), pp. 278-279, 2009.02. |
| 68. | Y. Fujii, S. Tanaka, Y. Yamagata, K. Muraoka, Simultaneous decompositions of diesel particulate materials and nitric oxides using dielectric barrier discharge in closed cycle, Proceedings of Plasma Science Symposium 2009 and the 26th Plasma Processing Symposium (Nagoya, Japan, February 2-4, 2009), pp. 70-71, 2009.02. |
| 69. | Yukihiko Yamagata, Yosuke Fujii, Yozo Kawagashira, Katsunori Muraoka, Decomposition of electrostatic-precipitated particulate materials from Diesel exhaust gas with nitric oxides using dielectric barrier discharge, Przeglad Elektrotechniczny, 85, 5, 127-130, 2009, Diesel particulate materials (DPM) in a real diesel exhaust gas were collected in a reactor using an electrostatic precipitation (ESP). Subsequently, the ESP-collected DPM were treated in the same reactor by a dielectric barrier discharge in a model gas including NO molecules. It was suggested that actual DPM and NO acting as the oxidant and reductant, respectively, were decomposed simultaneously and effectively by DBD.. |
| 70. | Y. Yamagata, Y. Fujii, K. Muraoka, Decomposition of electrostatic-precipitated diesel particulate materials with nitric oxides using dielectric barrier discharge, Bulletin of the American Physical Society, Vol. 53, No. 10, p. 67, 2008.10. |
| 71. | K. Tomita, Y. Yamagata, K. Uchino, Thomson Scattering Diagnostics of Microplasmas, Proceedings of ICPP2008 Satellite Meeting on Plasma Physics and Advanced Applications in ASO (Kumamoto, Japan, Oct. 12-14, 2008), pp.48-49, 2008.10. |
| 72. | K. Uchino，S. Nishimoto, A. Akune, Y. Sonoda, K. Tomita, S. Hassaballa, Y. Yamagata, Thomson Scattering Diagnostics of Dielectric-Barrier-Discharge Plasmas, Proceedings of The 3rd International School of Advanced Plasma Technology (Varenna, Italy, Jul. 28-31, 2008), pp.101-102, 2008.07. |
| 73. | Y. Yamagata, Y. Fujii, Y. Kawagashira, K. Muraoka, Decomposition of electrostatic-precipitated particulate materials from diesel exhaust gas with nitric oxides using dielectric barrier discharge, Proceedings of the 6th International Conference on Electromagnetic Devices and Processes in Environment Protection (Naleczow, Poland, June 24-27, 2008), pp. 49-50, 2008.06. |
| 74. | Y. Kawagashira, Y. Fujii, Y. Yamagata, K. Muraoka, Simultaneous decompositions of nitric oxides and electrostatic-precipitated diesel particulate materials and using dielectric barrier discharge, The 25th Plasma Processing Symposium (Yamaguchi, Japan) , pp. 239-240, 2008.01. |
| 75. | M. Naka, Y. Egashira, D. Kijima, A. H. A. Samir, K. Tomita, Y. Yamagata, K. Uchino, Y. Manabe, T. Ueda, Emission characteristics of Ba atom and thermionic electron from electrode of low-pressure fluorescent lamp, The 25th Plasma Processing Symposium (Yamaguchi, Japan) , pp. 329-330, 2008.01. |
| 76. | T. Ueda, A. Samir, Y. Egashira, G. Yamashita, S. Shimada, Y. Yamagata, K. Uchino, Y. Manabe, Effect of Glow-to-Arc Transition on Loss Mechanism of Ba Atoms from Electrode of Fluorescent Lamp, Japanese Journal of Applied Physics, Vol. 46, No. 10A, pp. 6828-6830, 2007.10. |
| 77. | Y. Yamagata, Y. Kawagashira, K. Muraoka, Development of simultaneous decomposition technique of diesel particulate materials and nitric oxides using dielectric barrier discharge, The 60th Annual Gaseous Electronics Conference (Arlington, VA, USA), SRP1-56, p. 65, 2007.10. |
| 78. | Takashi Ueda, Ahmed Samir, Yuichi Egashira, Go Yamashita, Shozaburo Shimada, Yukihiko Yamagata, Kiichiro Uchino, Yoshio Manabe, Effect of glow-to-arc transition on loss mechanism of Ba atoms from electrode of fluorescent lamp, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.1143/JJAP.46.6828, 46, 10 A, 6828-6830, 2007.10, The loss of Ba atoms from the electrode of a fluorescent lamp was measured while the lamp was operated in the glow and arc discharge modes at 60 Hz. A laser-induced fluorescence (LIF) technique was applied to the measurements of the temporal and spatial distributions of Ba atoms in the vicinity of the electrode. Ground-state (61S0) Ba atoms were excited to a 51P1 level by a frequency-doubled dye laser beam (350.1 nm), and the subsequent fluorescence (51P1-5 1D2, 582.6nm) was detected. The temporal and spatial distributions of Ba atoms were found to be completely different in the two discharge modes. Temporally; in the arc discharge mode, the density of the Ba atoms was found to have two peaks, and the number of Ba atoms emitted in the anode half-cycle was about twofold larger than that emitted in the cathode half-cycle. In the glow discharge mode, the number of Ba atoms emitted in the anode half-cycle was found to be negligible compared with that emitted in the cathode half-cycle. Spatially; in the arc discharge mode, Ba atoms were found to be emitted mainly from the hot spot of the filament electrode. In the glow discharge mode, Ba atoms were found to be emitted from all parts of the filament electrodes homogeneously. The mechanism of Ba atom loss in both modes was discussed.. |
| 79. | T. Ueda, Y. Egashira, M. Naka, A. Samir, Y. Manabe, Y. Yamagata, K. Uchino, Study of emitter material dynamics in a low-pressure fluorescent lamp by laser-induced fluorescence, Proceedings of the 13th International Symposium on Laser-Aided Plasma Diagnostics (Takayama, Japan, September 18-21, 2007), pp. 174-177, 2007.09. |
| 80. | K. Muraoka, K. Suzuki, M. Azumi, Y. Yamagata, M. Yagi, Simple analytical expression for electron temperature in an alternating current plasma display discharge, Journal of Applied Physics, Vol. 102, No. 4, pp. 043301-1-4, 2007.09. |
| 81. | K. Muraoka, K. Suzuki, M. Azumi, Y. Yamagata, M. Yagi, A simple analytical expression for electron temperature in an ac plasma display discharge, Proceedings of the 13th International Symposium on Laser-Aided Plasma Diagnostics (Takayama, Japan, September 18-21, 2007), pp. 161-165, 2007.09. |
| 82. | A. Samir, G. Yamashita, Y. Egashira, S. Shimada, Y. Yamagata, K. Uchino, T. Ueda, Y. Manabe, Loss of Ba Atom from the Electrode of Fluorescent Lamp Operating under AC and DC Discharges, 電気学会論文誌A分冊, 第127巻, 第9号, pp. 543-548, 2007.09. |
| 83. | K. Muraoka, K. Suzuki, M. Azumi, Yukihiko Yamagata, M. Yagi, Simple analytical expression for electron temperature in an alternating current plasma display discharge, Journal of Applied Physics, 10.1063/1.2769268, 102, 4, 2007.09, A simple analytical expression was derived for electron temperature Te in discharge conditions typical for an alternating current plasma display panel discharge, in which the least possible number of parameters was introduced so as to provide good physical insight into the mechanisms of determining Te under various discharge conditions. From this derivation, an explicit dependence of Te on discharge parameters (gas composition and pressure, and the strength of the electric field E) has been derived. It was tested for a discharge condition studied in our previous article on the discharge-radiation dynamics, yielding reasonable values for a cathode fall and a positive column. Also, the values of Te obtained experimentally using laser Thomson scattering in a positive column are well predicted from this analysis.. |
| 84. | Y. Egashira, A. Samir, G. Yamashita, K. Tomita, Y. Yamagata, K. Uchino, Y. Manabe, T. Ueda, Ba atom sublimation from the fluorescent lamp electrode during the operation by AC and DC discharges, Proceedings of the 18th International Symposium on Plasma Chemistry (Kyoto University, Japan, August 26-31, 2007), 31A-a3, pp. 1-4, 2007.08. |
| 85. | T. Ueda, Y. Egashira, A. Samir, Y. Yamagata, K. Uchino, Y. Manabe, The effect of discharge mode on Ba atom loss from the electrode of a low-pressure fluorescent lamp, Proceedings of the XXVIII International Conference on Phenomena in Ionized Gases (Prague, Czech Republic, July 15-20, 2007), pp. 1243-1246, 2007.07. |
| 86. | Y. Manabe, T. Ueda, A. S. Alyhendy, G. Yamashita, Y. Yamagata, K. Uchino, Characterization of Ba Atom Emission From Fluorescent Lamp Filament by Laser-Induced Fluorescence Technique, Proceedings of the 11th International Symposium on the Science and Technology of Light Sources (May 20th-24th, 2007, Shanghai, China) , CP005, pp. 45-46, 2007.05. |
| 87. | Koji Inoue, Keimei Furuki, Hiroshi Okano, Yukihiko Yamagata, Katsunori Muraoka, A new decomposition system for volatile organic compounds using combinations of dielectric barrier discharges with zeolite honeycomb sheets, IEEJ Transactions on Fundamentals and Materials, 127, 6, 2007, A new decomposition system for volatile organic compounds (VOCs), based on dielectric barrier discharges combined with zeolite honeycomb sheets, has been developed. A discharge element was made of layered flat metal sheets covered with mica sheets separated by 2 mm, in which corrugated (honeycomb-shaped) ceramic sheets embedded with zeolites .were inserted. This element was shown to satisfy the requirements of durability and flexibility to meet various sizes. Barrier discharges were investigated using this discharge element over wide ranges of operating conditions, in terms of the power consumption and decompositions of various types of VOCs. By selecting suitable operating scenarios, it was found that decomposition of more than 90 % of most VOCs were possible, at reasonable power consumption and without electrode contamination by decomposition products. Finally, areas of competitive applications of the present system against existing decomposition systems are also discussed. volatile organic compounds, dielectric barrier discharge, zeolite, adsorption, honeycomb sheet.. |
| 88. | Ahmed Samir, Go Yamashita, Yuichi Egashira, Shozaburo Shimada, Yukihiko Yamagata, Kiichiro Uchino, Yoshio Manabe, Takashi Ueda, Loss of Ba atom from the electrode of fluorescent lamp operating under AC and DC discharges, IEEJ Transactions on Fundamentals and Materials, 10.1541/ieejfms.127.543, 127, 9, 2007, Low work function is a vital life-determining characteristic of fluorescent lamp electrodes. The work function of a fluorescent lamp electrode increases due to the loss of Ba atom from the electrode. Hence the rate of Ba atom loss controls the lifetime of the lamp. However the loss mechanism and the optimum discharge condition has not been well understood yet. In the study, the loss of Ba atom from a fluorescent lamp electrode using a laser-induced fluorescence (LIF) technique is investigated. The lamp was operated at both AC 60 Hz and DC discharge modes with different discharge currents. In addition, the electrode of fluorescent lamp was connected through an external DC current source to control the electrode temperature. The effects of both the discharge current and the electrode temperature on the emission of Ba atom were investigated. For the lamp operation at 60 Hz, the physical behavior of the emission of Ba atom from the anode and the cathode were found to be different. The most of the loss of Ba atom was observed in an anode half-cycle, while this loss was lower in a cathode half-cycle. In the case of DC discharge, with increase in the discharge current, the loss of Ba atom was increased at the anode while it was decreased at the cathode. At the cathode the decrease in temperature was due to the electron emission from the cathode, which is called as "electron cooling" and it played an important role for the suppression of the Ba atom loss. Additionally, the sputtering of Ba atom due to ion bombardment was also considered to be an important factor for the loss of Ba atom from the cathode at a low discharge current.. |
| 89. | A. S. AlyHendy, G. Yamashita, Y. Yamagata, K. Uchino, T. Ueda, Y. Manabe, Study on Temporal and Spatial Distributions of Ba Atoms in a Fluorescent Lamp Discharge Using Laser-Induced Florescence, Japanese Journal of Applied Physics, Vol. 45, No. 10B, pp.8109-8112, 2006.10. |
| 90. | Y. Yamagata, K. Niho, K. Inoue, H. Okano, K. Muraoka, Decomposition of volatile organic compounds at low concentrations using combination of densification by zeolite adsorption and dielectric barrier discharge, Japanese Journal of Applied Physics, Vol. 45, No. 10B, pp.8251-8254, 2006.10. |
| 91. | M. A. Mansour, A. Nakamura, Y. Yamagata, K. Uchino, Measurements of Electron Energy Distribution Functions of Pulse-Modulated Argon and Argon-Oxygen Inductively Coupled Plasma Using Laser Thomson Scattering, Japanese Journal of Applied Physics, Vol. 45, No. 10B, pp.8118-8122, 2006.10. |
| 92. | Yukihiko Yamagata, Kouichiro Niho, Kouji Inoue, Hiroshi Okano, Katsunori Muraoka, Decomposition of volatile organic compounds at low concentrations using combination of densification by zeolite adsorption and dielectric barrier Discharge, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.1143/JJAP.45.8251, 45, 10 B, 8251-8254, 2006.10, The decomposition of toluene at very low concentrations (10-20ppm) using a combination of densification by zeolite adsorption and dielectric barrier discharge (DBD) was investigated. The characteristics of toluene decomposition using DBD under open and closed-loop flow conditions were determined. Under the closed-loop gas flow condition, a high decomposition ratio (70-93%) and a high energy efficiency [8-19g/(kWh)] were achieved for the adsorbed toluene (63% of the initial amount) by DBD treatment even at a high flow rate of 150L/min. Also, by the periodic operation of adsorption/DBD treatment, it was demonstrated that DBD treatment regenerated the honeycomb sheet containing zeolites for subsequent adsorption. The usefulness of this method for the decomposition of hazardous materials at low concentrations was shown.. |
| 93. | Mansour A M El-Sabbagh, Akinobu Nakamura, Toshiro Yanagai, Yukihiko Yamagata, Kiichiro Uchino, Measurements of electron energy distribution functions in pulse-modulated Ar and Ar/O2 inductively coupled plasmas using laser Thomson scattering, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.1143/JJAP.45.8118, 45, 10 B, 8118-8122, 2006.10, The time-resolved electron energy distribution functions (EEDFs) in Ar and Ar/O2 pulse-modulated inductively coupled plasmas have been measured in the afterglow for the first time using laser Thomson scattering. The measurements were performed for RF powers of 100 and 500 W at a frequency of 13.56 MHz, a duty cycle of 50%, and a pulse repetition frequency of 12.5 kHz. The Ar pressures were 20 and 100 mTorr at a flow rate of 132 seem, and the Ar/O2 (10% O2) pressure was 20 mTorr at a flow rate of 132 sccm. The measured EEDFs were all Maxwellian for the Ar and Ar/O2 (10% O2) plasmas. The Maxwellian distributions in the afterglow may be attributed to electron-electron collisions.. |
| 94. | Ahmed Samir AlyHendy, Go Yamashita, Yukihiko Yamagata, Kiichiro Uchino, Takashi Ueda, Yoshio Manabe, Study on temporal and spatial distributions of Ba atoms in fluorescent lamp discharge using laser-induced florescence, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.1143/JJAP.45.8109, 45, 10 B, 8109-8112, 2006.10, A laser-induced fluorescence (LIF) technique was applied to the measurements of the temporal and spatial distributions of Ba atoms in the vicinity of the electrode of a fluorescent lamp operated at 60 Hz. Ground-state (61S0) Ba atoms were excited to a 51P 1 level (350.1 nm) by a frequency-doubled dye laser beam, and the subsequent fluorescence (51P1-51D2, 582.6 nm) was detected. Over a whole periodic time (16.67 ms), the density of the Ba atoms was found to have two peaks, and the number of Ba atoms emitted in the anode half-cycle was about twofold larger than that emitted in the cathode half-cycle. This difference between the Ba atoms emitted during the anode half-cycle and those emitted during the cathode half-cycle was studied for lamps with different gas pressures. Ba atoms were found to be emitted mainly from the hot spot of the filament electrode. It is suggested that the main factor for Ba atom emission from the electrode is not sputtering by ion bombardment but thermal evaporation.. |
| 95. | Yukihiko Yamagata, Koichiro Niho, Toshifumi Jono, Yozo Kawagashira, Katsunori Muraoka, Simultaneous decomposition of diesel particulate material and NOx using dielectric barrier discharge, Journal of Advanced Oxidation Technologies, 9, 2, 133-138, 2006.07, We propose a new technique for simultaneous decomposition of diesel particulate material (DPM) and nitric oxides (NOx) exhausted from a diesel engine. DPM and NOx are collected in a reactor using an electrostatic precipitation and a honeycomb-shaped adsorbent, respectively. After the sufficient collections, a dielectric barrier discharge (DBD) is generated in the closed space to condense and decompose DPM and NOx. DPM and NOx were decomposed simultaneously and effectively by the DBD, which act as the oxidant and reductant, respectively. It is considered that this technique is the most suitable for the decomposition of DPM and NOx with small concentration and high gas flow rate.. |
| 96. | Y. Yamagata, K. Niho, T. Jono, K. Muraoka, Simultaneous decomposition of diesel particulate material and NOx using dielectric barrier discharge, Journal of Advanced Oxidation Technologies, Vol. 9, No. 2, pp. 134-138, 2006.06. |
| 97. | K. Muraoka, M. Azumi, K. Suzuki, Yukihiko Yamagata, M. Yagi, A model for striation formation in ac PDP discharges, Journal Physics D: Applied Physics, 10.1088/0022-3727/39/10/025, 39, 10, 2135-2139, 2006.05, A model is presented to explain the mechanism of striation formation in ac plasma display panel discharges. A simple Monte-Carlo simulation code was used to follow electron motion in such discharges. The obtained features of striations, such as a striation pitch, striated accumulation of charged particles on a dielectric surface above an anode and phase oppositions of electron density and average energy are consistent with previous experiments and numerical simulations. Comparison of the experimental and theoretical space pitch of the striations allows an indirect determination of the electric field.. |
| 98. | K. Muraoka, M. Azumi, K. Suzuki, Y. Yamagata, M. Yagi, A model for striation formation in ac PDP discharges, Journal of Physics D : Applied Physics, Vol. 39, pp. 2135-2139., 2006.03. |
| 99. | Y. Yamagata, K. Niho, T. Jono, K. Muraoka, Simultaneous decomposition of DPM and NOx using dielectric barrier discharge, Proceedings of the 5th International Conference on Electromagnetic Devices and Processes in Environment Protection (Naleczow, Poland, September 4-6, 2005), 9, 2, 134-138, pp. 160-165, 2005.09. |
| 100. | H. Naitou, Y. Sakurai, Y. Tauchi, O. Fukumasa, M. Yagi, Yukihiko Yamagata, Kiichiro Uchino, K. Muraoka, Simulation of photo-detached electrons in negative ion plasmas, Plasma Physics and Controlled Fusion, 10.1088/0741-3335/46/8/004, 46, 8, 1217-1230, 2004.08, The evolution of laser photo-detached and background electrons in a glow discharge plasma containing negative ions was followed using a two-dimensional particle-in-cell simulation code. Emphasis was placed on the short timescale (20ns after photo-detachment for the parameters of a typical glow discharge plasma) behaviour because this is the timescale of the recently developed laser Thomson scattering technique combined with photo-detachment. A plasma consisting of background electrons, positive argon ions (Ar+) and negative oxygen ions (O-) was treated. The loss of photo-detached electrons from the photo-detachment region quickly forms a potential structure in a short time of 2ns. The potential traps the remaining photo-detached electrons. The profile of the trapped photo-detached electrons is hollow. The loss of the photodetached electrons from the photo-detachment region is compensated by the bulk electrons coming from the ambient plasma; the sum of the photo-detached and bulk electron densities in the photo-detachment region remains unchanged for 20 ns because ions are almost immobile in this timescale. This analysis has also revealed the fractions of the photo-detached electrons remaining in the photo-detachment region during the 20 ns to be relatively insensitive to a change in laser beam size and very sensitive to the relative densities of negative ions against background electrons, and to the shape of the velocity distribution function at different angles with respect to the laser beam axis.. |
| 101. | H. Naitou, Y. Sakurai, Y. Tauchi, O. Fukumasa, M. Yagi, Y. Yamagata, K. Uchino, K. Muraoka, Simulation of photo-detached electrons in negative ion plasmas, Plasma Physics and Controlled Fusion, 10.1088/0741-3335/46/8/004, 46, 8, 1217-1230, Vol. 46, pp. 1217-1230, 2004.07. |
| 102. | Yukihiko Yamagata, Takafumi Matsui, Takashi Ebihara, Katsunori Muraoka, Decomposition of diesel particulate materials and nitric oxides using a dielectric barrier discharge, Quaternary International, 178, 367-372, 2004, We have demonstrated the usefulness of a trapping-filter trapping-low temperature burning scheme for diesel particulate materials (DPM) aftertreatment in an actual diesel exhaust gas using a dielectric barrier discharge (DBD). The DPM trapped by a mesh electrode were decomposed to CO and CO2 molecules using the DBD. Simultaneous decomposition of the DPM and nitric oxides in diesel exhaust gas is also presented.. |
| 103. | Kenji Ebihara, Takahiro Tanaka, Tomoaki Ikegami, Yukihiko Yamagata, Toru Matsunaga, Kazutaka Yamashita, Yoshifumi Oyama, Application of the dielectric barrier discharge to detect defects in a teflon coated metal surface, Journal Physics D: Applied Physics, 10.1088/0022-3727/36/23/003, 36, 23, 2883-2886, 2003.12, In the semiconductor industry, flexible stainless steel tubes, the inside of which are coated with thick Teflon films, by the splay coating method, have been used to prevent their degradation and erosion by organic solvents. We have developed an inspection system to detect pinholes and cracks in the deposited Teflon films, and the dielectric barrier discharge (DBD) was employed to reduce residual substances and damages to the coated film in the tube. Conducting water contained in the cylinder-like glass pipe was used as a liquid electrode to apply a high voltage at any portion of the tube tested. A defective part with a pinhole was modelled by a point electrode in this experiment, because the uncoated defective part has a lower electric breakdown voltage. High frequency voltage (10 kHz) was applied between the point electrode and the liquid electrode. The level of the liquid electrode was varied to detect the occurrence of a microdischarge. It is found that the number of current pulses due to the microdischarge can be used to estimate the size and location of the defective uncoated point of the sample tube.. |
| 104. | K. Ebihara, F. Tanaka, T. Ikegami, Y. Yamagata, T. Matsunaga, K. Yamashita, Y. Oyama, Application of the dielectric barrier discharge to detect defects in a teflon coated metal surface, Journal Physics D: Applied Physics, 10.1088/0022-3727/36/23/003, 36, 23, 2883-2886, Vol. 36, pp. 2883-2886, 2003.08. |
| 105. | M. Noguchi, T. Hirao, M. Shindo, K. Sakurauchi, Y. Yamagata, K. Uchino, Y. Kawai, K. Muraoka, Comparative studies of the laser Thomson scattering and Langmuir probe methods for measurements of negative ion density in a glow discharge, Plasma Sources Science and Technology, 10.1088/0963-0252/12/3/314, 12, 3, 403-406, Vol. 12, No. 3, pp. 403-406, 2003.08. |
| 106. | M. Noguchi, T. Hirao, M. Shindo, K. Sakurauchi, Yukihiko Yamagata, Kiichiro Uchino, Y. Kawai, K. Muraoka, Comparative studies of the laser Thomson scattering and Langmuir probe methods for measurements of negative ion density in a glow discharge plasma, Plasma Sources Science and Technology, 10.1088/0963-0252/12/3/314, 12, 3, 403-406, 2003.08, The newly developed method of the negative ion density measurement in a plasma by laser Thomson scattering (LTS) was checked by comparing the obtained results against an independent technique, namely the Langmuir probe method. Both measurements were performed at the same position of the same inductively coupled plasma. The results agree quite well with each other and this has given confidence in the LTS method of negative ion density measurement. At the same time, both methods are complementary to each other, because the Langmuir probe measurement requires knowledge of the positive ion mass number.. |
| 107. | M. Noguchi, T. Hirao, K. Sakurauchi, Y. Yamagata, H. Naitou, M. Yagi, K. Uchino, K. Muraoka, One-Dimensional Simulation of Photo-Detached Electrons in Negative Ion Plasmas, Journal of Plasma Fusion Research, Vol. 79, No. 3, pp.274-281, 2003.03. |
| 108. | Y. Yamagata, K. Murayama, T. Ikegami, K. Ebihara, Characteristics of Nitric Monoxide Generation Using High Frequency Silent Discharge, Journal of Advanced Oxidation Technologies, 6, 1, 55-61, Vol. 6, No. 1, pp. 55-61, 2003.01. |
| 109. | K. Muraoka, K. Uchino, Y. Yamagata, Y. Noguchi, P. Suanpoot, S. Narishige, M. Noguchi, Laser Thomson scattering studies of glow discharge plasmas, Plasma Sources Science and Technology, 10.1088/0963-0252/11/3A/321, 11, 3A, A143-A149, Vol. 11, No. 8, pp. A143-A149, 2002.08. |
| 110. | K. Muraoka, Kiichiro Uchino, Yukihiko Yamagata, Y. Noguchi, M. Mansour, P. Suanpoot, S. Narishige, M. Noguchi, Laser Thomson scattering studies of glow discharge plasmas, Plasma Sources Science and Technology, 11, 3 A, 2002.08, This paper describes the developments of laser Thomson scattering (LTS) for measuring electron density and temperature, or more generally electron energy distribution function (eedf) in glow discharge plasmas with electron densities below 1018 m-3. A brief description of the method for overcoming the sparcity of scattered photons by data accumulation techniques is followed by examples of applications, conducted at the authors' laboratory, to the measurement of the shape of the eedf and temperature anisotropy in various discharges including reactive plasmas, and some as close as 100 μm from a material surface. Measurements of the latter sort should permit the elucidation of micro-discharges and electrode effects such as cathode fall phenomena in particular.. |
| 111. | M. Noguchi, K. Ariga, T. Hirao, P. Suanpoot, Y. Yamagata, K. Uchino, K. Muraoka, Laser Thomson scattering measurements of negative ion density in a glow discharge plasma, Plasma Sources Science and Technology, 10.1088/0963-0252/11/1/307, 11, 1, 57-59, Vol. 11, No. 3, pp. 57-59, 2002.03. |
| 112. | P. Suanpoot, S. Narishige, Y. Yamagata, K. Uchino, K. Muraoka, M. Noguchi, Applicabilities of laser Thomson scattering to various kinds of discharge plasmas, Journal of Plasma Fusion Research, Vol. 78, No. 3, pp.242-247, 2002.03. |
| 113. | M. Noguchi, K. Ariga, T. Hirao, P. Suanpoot, Yukihiko Yamagata, Kiichiro Uchino, K. Muraoka, Laser Thomson scattering measurements of negative ion density in a glow discharge plasma, Plasma Sources Science and Technology, 10.1088/0963-0252/11/1/307, 11, 1, 57-59, 2002.02, Laser Thomson scattering (LTS) is shown to provide a useful means for measurements of negative ion density in a glow discharge plasma. Because the saturation energy density is so low that complete photo-detachment occurs at a very early stage of the probing laser pulse for the LTS measurement, the main part of the laser pulse is Thomson scattered by the photo-detached electrons as well as those already generated in the discharge. The energies of photo-detached electrons are below the energy difference between the photon energy and the electron affinity of the negative ions, and Thomson scattering from these appears below the difference energy. The principle has been tested using the second harmonic of a YAG laser light (532 nm) against an inductively coupled plasma operated in a mixture of Ar(80%)/O2(20%) at a pressure of 20 mTorr, and yielded the negative ion density of 1.5 × 1017 m-3, which amounted to 37% of the electron density of 4.1 × 1017 m-3 or 27% of the negative charges (electrons and negative ions).. |
| 114. | T. Ohshima, R. K. Thareja, Yukihiko Yamagata, T. Ikegami, K. Ebihara, J. Narayan, Laser-ablated plasma for deposition of ZnO thin films on various substrates, Science and Technology of Advanced Materials, 10.1016/S1468-6996(01)00132-2, 2, 3-4, 517-523, 2001.09, We report optical and structural properties of ZnO films deposited by pulsed laser deposition technique on (100) n-type silicon and quartz substrates at various pressures of back ground gas. ZnO plasma was created using KrF laser (248 nm) at various pressures of the ambient gas, oxygen. Laser induced plasma at varying fluence on the target was investigated using optical emission spectroscopy and 2-D images of the expanding plumes. X-ray diffraction, atomic force microscopy, and spectro-photometry were used to characterize as grown films.. |
| 115. | T. Ikegami, S. Ishibashi, Yukihiko Yamagata, K. Ebihara, R. K. Thareja, J. Narayan, Spatial distribution of carbon species in laser ablation of graphite target, Journal of Vacuum Science and Technology A, 10.1116/1.1381403, 19, 4, 1304-1307, 2001.07, The spatial distribution of carbon species produced by laser ablation of a graphite target was studied using laser induced fluorescence imaging and optical emission spectroscopy. Two-dimensional fluorescence of ambient gases at various pressures, laser fluences and ablation area were used to measure spatial density profiles of C2. The yield of C2 was large at center of the plume and near the target surface while that of C3 in argon gas increased at higher gas pressure and longer delay times after ablation.. |
| 116. | Tamiko Ohshima, R. K. Tareja, 山形 幸彦, Tomoaki Ikegami, Kenji Ebihara, J. Narayan, Laser-ablated plasma for deposition of ZnO thin films on various substrates, Science and Technology of Advanced Materials, Vol. 2, No, 3-4, 517-523, 2001.03. |
| 117. | T. Ikegami, T. Maezono, F. Nakanishi, Yukihiko Yamagata, K. Ebihara, Estimation of equivalent circuit parameters of PV module and its application to optimal operation of PV system, Solar Energy Materials and Solar Cells, 10.1016/S0927-0248(00)00307-X, 67, 1-4, 389-395, 2001.03, A method to estimate the equivalent circuit parameters of a PV (photovoltaic) module is presented. The parameters are calculated using a least-squares fitting of the equivalent model current-voltage characteristic with the measured one. For applications of the equivalent circuit model parameters, a quantitative diagnostic method of the PV modules by evaluating the parameters is introduced and examined by simulation. A new maximum peak power tracking (MPPT) method using the model parameters, a solar insolation, and a cell temperature is also shown. Its performance is compared with other MPPT control algorithms by simulations. The performance of the proposed method was better than other MPPT methods.. |
| 118. | Yukihiko Yamagata, Tamiko Ohshima, Tomoaki Ikegami, Raj K. Thareja, Kenji Ebihara, Ajay Sharma, Robert M. Mayo, Jagdish Narayan, Characteristics of laser-ablated plasma and properties of diamond-like carbon film in pulsed laser deposition, Materials Research Society Symposium - Proceedings, 648, P6551-P6556, 2001, Characteristics of laser-ablated carbon plasma and properties of diamond-like carbon film in KrF pulsed laser deposition were investigated using laser-induced fluorescence (LIF) and optical emission spectroscopy. Two-dimensional LIF images of C2 (Swan band, d3Πg - a 3Πu) and C3 (Comet Head System, A 1Πu-X 1 σg+) molecules were detected as a function of laser energy density by narrow band pass filters and an intensified CCD camera. C2 LIF intensity is found to be weaker in the central part of the plume than that at the periphery at incident energy greater than 6 J/cm2. It is conjectured that C2 molecules are dissociated by collision with energetic species in the central part of the ablation plume, and degrade the diamond-like property of deposited films.. |
| 119. | Tamiko Ohshima, Raj K. Thareja, Yukihiko Yamagata, Tomoaki Ikegami, Kenji Ebihara, Optical and structural properties of zinc-oxide thin film deposited by pulsed laser deposition, Quaternary International, 666, 2001, We report optical and structural properties of ZnO films deposited by pulsed laser deposition technique on silicon (100) n-type, quartz, sapphire, and coming glass substrates. We have studied the influence of the deposition parameters, such as substrate temperature, oxygen pressure, and laser fluence on the properties of the grown films. Dependence of nanocrystallites on temperature of substrate and ambient gas pressure is investigated. ZnO plasma created at varying fluence of KrF laser (248 nm) on the target was investigated using optical emission spectroscopy and 2-d images of the expanding plumes at various pressures of the ambient gas. X-ray diffraction, atomic force microscopy, electron probe micro-analyzer, and spectro-photometry were used to characterize as grown films.. |
| 120. | R. M. Mayo, J. W. Newman, Yukihiko Yamagata, A. Sharma, J. Narayan, Comparative study of pulsed laser ablated plasma plumes from single crystal graphite and amorphous carbon targets. Part II. Electrostatic probe measurements, Journal of Applied Physics, 10.1063/1.1321784, 88, 11, 6868-6874, 2000.12, In an ongoing effort to investigate plasma plume features yielding high quality diamond-like carbon films, we have applied plasma plume diagnosis and film characterization to examine plume character distinction from KrF laser ablation of both amorphous carbon (a-C) and single crystal graphite (SCG) targets. The advancing plasma plume produced by these structurally different targets are observed to possess quantitatively similar total heavy particle inventory, ionized fraction, and electron thermal content, yet quite different ion kinetic energy, plume profile, C2 formation mechanism, and concentration of complex molecules. Plume electron temperatures are observed to reside in the range 1-3 eV, with those in SCG plumes ∼10%-30% greater than a-C at all spatial positions downstream of the target. For both target cases, we find Te drop off with position away from the target with radiation as the most likely loss mechanism for these noninteracting plumes propagating in vacuum. Electron density is found to be ∼10%-12% lower near the target in SCG than a-C plumes consistent with mass loss inventory measurements, whereas ion fractions are estimated in the range ∼10%-15% for both target cases. All recorded data support the conclusion that the SCG target plasma plume is populated with heavier, more complex molecules than those in a-C which have been shown to be predominantly comprised of C and C+ under vacuum conditions with the addition of C2 at high fill pressure. A significantly smaller profile peaking factor for SCG plumes supports this conclusion. Less energetic and slightly lower temperature SCG plume conditions are consistent with reduced peaking and more massive plume species. Plasma plumes from SCG targets exhibit laser energy (El) dependent peaking, again consistent with more complex molecules increasingly disassociated with El increase. The El dependence further suggests the potential for control of particle size distribution and plume profile peaking, though not independently. Consistent with this scenario is the observation of harder films produced from SCG targets at lower El. Micro-Raman results indicate strongly heterogeneous films deposited by SCG target ablation even under vacuum conditions further supporting the case for more complex structures with greater hardness. Energy balance estimates indicate that ion kinetic energy dominates the balance and that SCG ablation liberates about twice the number of 12C atoms from the target per unit El. As well, high pressure background fill indicates lesser plume energy attenuation for SCG plumes, again suggesting the presence of higher mass particles.. |
| 121. | Yukihiko Yamagata, A. Sharma, J. Narayan, R. M. Mayo, J. W. Newman, K. Ebihara, Comparative study of pulsed laser ablated plasma plumes from single crystal graphite and amorphous carbon targets. Part I. Optical emission spectroscopy, Journal of Applied Physics, 10.1063/1.1321783, 88, 11, 6861-6867, 2000.12, A comparative study of ablation plasma plumes originated from single crystal graphite (SCG) and amorphous carbon (a-C) targets during the preparation of diamond-like carbon (DLC) films by KrF excimer pulsed laser deposition (PLD) has been carried out by means of a monochromator equipped with an intensified optical multichannel analyzer. In high vacuum, the emission lines of carbon neutral C and ions of C+, C2+, and C3+ can be observed from both the SCG and a-C plasma plumes. The emission intensity from C atoms increases with laser energy density (EL) increase for both cases. The C2 emission intensity from the SCG plasma plume changes drastically with EL, while that from the a-C plasma plume is almost constant. The C2/C emission intensity ratio for the a-C case decreases with EL increase. As for the SCG case, the C2/C ratio decreases with EL increase up to 3.0 J/cm2, and increases slightly with further EL increase. Nanohardness of the deposited films decreases with the increase of the C2/C emission intensity ratio. It is suggested that for both the SCG and a-C target cases, the C2 molecule in the ablated plasma plume may not play an important role in producing high quality DLC films. It is further proposed that the threshold of laser fluence for the formation of diamond-like character film using KrF excimer PLD is 2.1 J/cm2(0.84 × 108 W/cm2) for the a-C target and 3.0 J/cm2(1.2 × 108 W/cm2) for the SCG target. The C2 vibrational temperature of the SCG and the a-C plasma plumes show different features on both the laser energy density and nitrogen pressure dependencies. Through optical emission spectroscopy and Langmuir probe measurements in vacuum and nitrogen background, it is concluded that there are many particles with higher mass in the SCG plasma plume, especially at relatively lower laser energy density below 3.0 J/cm2.. |
| 122. | R. M. Mayo, J. W. Newman, A. Sharma, Yukihiko Yamagata, J. Narayan, Plasma and DLC film characteristics from pulsed laser ablation of single crystal graphite and amorphous carbon A comparative study employing electrostatic probe measurements, Materials Research Society Symposium - Proceedings, 617, 2000.12, In an ongoing effort to investigate plasma plume features yielding high quality DLC films, we have applied plasma plume diagnosis and film characterization to examine plume character distinction from KrF laser ablation of both amorphous carbon (a-C) and single crystal graphite (SCG) targets. The advancing plasma plume produced by these structurally different targets are observed to possess quantitatively similar total heavy particle inventory, ionized fraction, and electron thermal content, yet quite different ion kinetic energy, plume profile, C2 formation mechanism, and concentration of complex molecules. All data support the conclusion that the SCG target plasma plume is populated with heavier, more complex molecules than those in a-C which have been shown to be predominantly comprised of C and C+ under vacuum conditions with the addition of C2 at high fill pressure. Significantly smaller plume profile peaking factor, less energetic and slightly lower temperature plume conditions, laser energy (El) dependent plume peaking, harder films produced at lower El, strongly heterogeneous films, and lesser plume energy attenuation in high pressure background fill in SCG target plumes all support the conclusion of more massive plume species in SCG target plumes. Energy balance estimates indicate that ion kinetic energy dominates and that SCG target ablation liberates about twice the number of 12C atoms per unit El.. |
| 123. | Fumiaki Mitsugi, Yukihiko Yamagata, Tomoaki Ikegami, Kenji Ebihara, Jagdish Narayan, Alexander M. Grishin, Ferroelectric and colossal magnetoresistive properties of a PbZr1-xTixO3/La1-xSrxMnO3 heterostructure film, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 39, 9 B, 5418-5420, 2000.09, We report the ferroelectric and magnetoresistive properties and crystallization of a PbZr0.52Ti0.48O3 (PZT)/La0.8Sr0.2MnO3 (LSMO) heterostructure film prepared by pulsed-laser deposition on a MgO(100) single crystal substrate. Ferroelectric properties such as the hysteresis loop and dielectric constant of the Au/PZT/LSMO capacitor were compared with those of the Au/PZT/YBa2Cu3O7-x (YBCO) superconductor heterostructure film. The resistivity of the LSMO film was as low as that of the YBCO film at room temperature. The fabricated Au/PZT/LSMO capacitor had a remanent polarization of 29 μC/cm2, a coercive field of 30 kV/cm and a dielectric constant of about 1000.. |
| 124. | Q. Wei, S. Yamolenko, J. Sankar, A. K. Sharma, Yukihiko Yamagata, J. Narayan, Microstructure and nanomechanical properties of amorphous carbon thin films prepared by pulsed laser deposition in various atmospheres, Materials Research Society Symposium - Proceedings, 10.1557/PROC-616-217, 616, 217-222, 2000.01, We have investigated the effect of chamber pressure and atmosphere on the microstructure and nanomechanical properties of amorphous diamondlike carbon (DLC) thin films prepared by pulsed laser deposition. The amorphous carbon films were deposited in various atmospheres such as nitrogen and argon at different pressures. We used Raman spectroscopy and optical microscopy to study the bonding characteristics and microstructures of the DLC films. Nanoindentation measurements were carried out on various samples prepared under different conditions to study the effect of chamber pressure and atmosphere on the elastic modulus and nano-hardness of the films. It was found that reduced vacuum leads to softer amorphous carbon films. Amorphous carbon films prepared in higher pressures exhibit increased density of particulates, and significantly rough surface. The results were understood in terms of thermalization of the laser plasma due to increased possibility of collision.. |
| 125. | R. M. Mayo, J. W. Newman, A. Sharma, Yukihiko Yamagata, J. Narayan, Electrostatic measurement of plasma plume characteristics in pulse laser ablated carbon, Quaternary International, 593, 261-266, 2000, A triple Langmuir probe measurement has been implemented to investigate plasma plume character in low fluence (approx. 3.0 J/cm2) pulsed laser evaporation (PLE) discharges and has been found to be an extremely valuable tool. Absolute plasma plume density estimates are found to reside in the range 1.0×1013-2.0×1014 cm-3 for vacuum pulses. A simple heavy particle streaming model for vacuum pulses allows estimates of the plume ionization fraction of approx. 10%. This is consistent with typical deposition inventory suggesting that high kinetic energy ions play an important role in DLC film deposition. Electron temperature is found to consistently reside in the range 0.5-3.0 eV, and appears to be uninfluenced by operating conditions and large variations in Ar and N2 fill gas pressure. Consistent with strong plume ion and neutral particle coupling to the background fill, constancy of Te suggests expulsion of background gas by the energetic plume. The leading edge ion plume speed is measured via temporal displacement of spatially separated probe signals on consecutive PLE pulses. Flow speeds as high as 5.0 × 104 m/s are observed, corresponding to approx. 156 eV in C+. The ion flow speed is found to be a strongly decreasing function of fill pressure from an average high of approx. 126 eV in vacuum to approx. 0.24 eV at 600 mTorr N2. Raman scattering spectroscopy indicates DLC film quality also degrades with fill pressure suggesting the importance of high ion kinetic energy in producing good quality films. Optical emission indicates an increase in C2 molecular light intensity with fill gas pressure implying a reduced, if any, role of these species in DLC production. Ion current signal anomalies in high pressure pulses indicate the formation of high mass carbon clusters during plume evolution in the presence of background gas. Mass diffusivity estimates, based on density decay, suggest the presence of C2 + under these conditions. Demonstration and control of such cluster formation may provide method(s) for controlling novel advanced materials properties.. |
| 126. | Yukihiko Yamagata, Yuji Kozai, Fumiaki Mitsugi, Tomoaki Ikegami, Kenji Ebihara, Ajay Sharma, Robert M. Mayo, Jagdish Narayan, Laser induced fluorescence measurement of plasma plume during pulsed laser deposition of diamond-like carbon, Materials Research Society Symposium - Proceedings, 10.1557/PROC-617-J3.4, 617, J341-J346, 2000, Dynamics of carbon ablation plasma plume during the preparation of diamond-like carbon films by KrF excimer pulsed laser deposition was investigated using laser induced fluorescence (LIF) and optical emission spectroscopy. LIF signal from C2 molecule (Swan band, d 3∏g - a 3∏u) was detected using a photomultiplier tube and an intensified CCD camera. Temporal evolution and spatial distribution of C2 molecules in the ablated plume were measured as a function of laser energy density and ablation area. LIF intensity is found to be weaker in the central part of the plume than that at the periphery at incident energy greater than 6 J/cm2. It is conjectured that some of C2 molecules are dissociated by collision with energetic species in central part of the ablation plume. Dynamics of ablation plasma plume is strongly dependent on the size of ablated area.. |
| 127. | Yukihiko Yamagata, A. Sharma, J. Narayan, R. M. Mayo, J. W. Newman, K. Ebihara, Plasma diagnostics during pulsed laser deposition of diamond-like carbon using single crystal graphite and amorphous carbon, Quaternary International, 593, 255-260, 2000, Optical emission study of ablation plasma plumes from single crystal graphite (SCG) and amorphous carbon (a-C) targets during the preparation of diamond-like carbon (DLC) films by KrF excimer pulsed laser deposition (PLD) has been investigated. The C I emission intensity increases with laser energy density (EL) increase, while the C2 emission changes drastically with EL for both ablated plasma plumes. The C2/C emission intensity ratio for the a-C plume decreases with EL increase, while the C2/C ratio for the SCG plume decreases with EL increase up to 3.0 J/cm2, then increases slightly with further EL increase. Nanohardness of the DLC films decreases with the C2/C ratio increase. It is suggested that the C2 molecule in the plasma plume does not play an important role in producing high quality DLC films, and that the C2/C ratio is a good parameter to monitor the PLD process.. |
| 128. | Yukihiko Yamagata, A. Sharma, J. Narayan, R. M. Mayo, J. W. Newman, K. Ebihara, Optical emission study of ablation plasma plume in the preparation of diamond-like carbon films by KrF excimer laser, Journal of Applied Physics, 10.1063/1.371340, 86, 8, 4154-4159, 1999.10, Optical emission study of the laser ablation plasma plume during the preparation of diamond-like carbon (DLC) films using KrF excimer (248 nm) pulsed laser deposition (PLD) has been carried out by means of a monochromator equipped with an intensified optical multichannel analyzer. In high vacuum (1 × 10-7 Torr), the emission lines from carbon ions of C+, C2+, and C3+ are observed in addition to atomic carbon emission lines, while no emission from the diatomic carbon molecule (C2) is observed. With increasing background nitrogen pressure up to 500 mTorr, the emission intensities of the C2 Swan band and the carbon nitride (CN) violet band increase. The diamond-like character of deposited DLC film degrades with background nitrogen pressure. The vibrational temperature of C2 and CN molecules decreases with the increasing of nitrogen pressure. The CN vibrational temperature for the first 2 μs after the laser pulse is very high and in agreement with the kinetic energy of monatomic carbon ions. The C2 vibrational temperature is as low as 0.6 eV and is consistent with the electron temperature of about 0.8-3.0 eV. It is conjectured that CN molecules are formed directly in reactions involving energetic ionic monatomic carbon, and that the formation of excited C2 molecules is the result of molecular recombinations of C atoms and ions. From the emission intensity measurements and the estimation of the vibrational temperature, it is suggested that the C2 molecule in the ablated plasma plume is not important, but energetic species, such as C+, are very important for producing high quality DLC films using PLD.. |
| 129. | K. Ebihara, F. Mitsugi, M. Yamazato, Yukihiko Yamagata, Diamond-like carbon film deposition on PZT ferroelectrics and YBCO superconducting films using KrF excimer laser deposition, Composites Part B: Engineering, 10.1016/S1359-8368(99)00033-5, 30, 7, 685-689, 1999.01, Ferroelectric PbZr0.52Ti0.48O3 (PZT) and superconducting YBa2Cu3O7-x (YBCO) thin films were coated by unhydrogenated diamond-like carbon (DLC) films in order to reduce the aging degradation. Excimer laser ablation technique is applied to prepare PZT, YBCO and DLC films. The 60 days aging degradation of the DLC coated YBCO structure is limited within only 10% decay of normal resistivity. The polarization-electric field characteristics of the ferroelectric capacitor Au/PZT/YBCO/MgO shows a remanent polarization of 23.2 μC/cm2 and a coercive field of 54.0 kV/cm. At least 10% decay of these ferroelectric values was observed after 60 days exposure to atmosphere.. |
| 130. | R. M. Mayo, J. W. Newman, A. Sharma, Yukihiko Yamagata, J. Narayan, Electrostatic measurement of plasma plume characteristics in pulsed laser evaporated carbon, Journal of Applied Physics, 10.1063/1.371135, 86, 5, 2865-2871, 1999.01, A triple Langmuir probe measurement was used to investigate plasma plume character in low fluence pulsed laser evaporation (PLE) discharges in diamond-like carbon film deposition. Initial findings from combined ion probe, visible spectroscopy, and film analysis is presented to provide a more detailed description of plasma plume characteristics and the relationship to film properties. Analytic modeling of the ion current in the supersonic plume allows an estimate of the ion number density throughout the plume.. |
| 131. | Yukihiko Yamagata, M. Yamazato, T. Ikegami, K. Ebihara, J. Narayan, A. M. Grishin, Control of ferroelectric properties of PbZrxTi1-xO3 thin film for electron emission device driven by low voltage, Materials Research Society Symposium - Proceedings, 541, 759-764, 1999, Epitaxial PbZr0.52Ti0.48O3/YBa2Cu3O7-x heterostructures on Nd:YAlO3 and MgO substrates were fabricated by KrF pulsed laser deposition. The coercive electric field of the PZT films increased with decrease of the film thickness from 1.2 μm to 0.04 μm, while the magnitude of spontaneous polarization was almost constant in this thickness range. It was found that the dependence of the film thickness d on the coercive electric field Ec was Ec ∝ d-2/3. This results from that the PZT/YBCO heterostructure has the one dimensional ferroelectric domain growth without non-ferroelectric phase. The polarization of Au/PZT/YBCO/(MgO or YAlO) capacitors can be changed by the applied voltage below 5 V.. |
| 132. | R. M. Mayo, J. W. Newman, A. Sharma, J. Narayan, Yukihiko Yamagata, Electrostatic measurement of plasma plume dynamics in pulsed laser evaporated graphite, Quaternary International, 97, 1999, Electrostatic (Langmuir) probe measurements were conducted in the carbon pulsed laser evaporation (PLE) plume to investigate plume dynamics and correlate against film properties. Preliminary results indicate electron densities on the order of 1012-1015 cm-3 and electron temperatures approximately 0.25-0.5 eV at 1 cm from the target surface. Plasma density is often observed to increase initially with probe-target separation distance before decreasing.. |
| 133. | K. Shingai, Yukihiko Yamagata, T. Ikegami, K. Ebihara, Preparation of superconducting multilayer structure for power electronic devices, Thin Solid Films, 10.1016/S0040-6090(97)01170-X, 318, 1-2, 247-251, 1998.04, Multi-step KrF excimer pulsed laser deposition (MSPLD) technique has been developed to fabricate high-quality micrometer thick superconducting YBa2Cu3O7-x (YBCO) films. As has been shown, a crystallization of YBCO at the initial stage of deposition crucially affects on thick YBCO film performance. Smooth, c-axis oriented 1-μm thick YBCO films with the critical temperature of Tc(zero) = 89.5 K and the overall critical current density of Jc(77 K) = 105 A/cm2 have been prepared on the single crystal MgO substrate in three-step process by monitoring the laser fluence, laser repetition rate and substrate temperature. Micrometer thick YBCO films on the single crystal LaAlO3 substrate show Tc(zero) = 85.7 K and Jc(77 K) = 103 A/cm2, indicating that optimization of MSPLD processing conditions is much more critical for substrates with a small substrate/film lattice mismatch. Furthermore, Pb(Zr,Ti)O3(PZT)/YBa2Cu3O7-x/MgO heterostructures have been prepared by MSPLD technique with the critical temperature of Tc(zero) = 82.0 K in superconducting YBCO layer.. |
| 134. | Shin Ichi Aoqui, Tomoaki Ikegami, Yukihiko Yamagata, Kenji Ebihara, Optical emission study of the laser plasma plume produced during diamondlike carbon thin film preparation, Thin Solid Films, 10.1016/S0040-6090(98)00385-X, 316, 1-2, 40-44, 1998.03, We have studied the application of the diamondlike carbon (DLC) film as a protective coating layer for high temperature superconducting thin films. Recently, the DLC film was proposed as an attractive material for field electron emitter device. We report on spectroscopic properties of the KrF laser plasma plume produced during the DLC thin film deposition. Optical emission measurements showed appearance of such neutral and ionic species as H, C, C+, CH, CH+, C2H+. Strong emission from neutral and ionic molecules CH, C2, C2H+ produced by the reaction in the gaseous phase has been observed with the ambient hydrogen gas pressure increase. The calculated velocities of CH and C2H+ molecules at the distances of 10-20 mm from the target are found to be 5.0 × 103 m/s and 9.1 × 103 m/s, correspondingly. The properties of the DLC thin films are strongly affected by the laser plasma plume dynamics. The DLC film deposited on MgO (100) at room temperature and 200 mTorr hydrogen pressure was almost transparent in the visible light range and had an optical band energy gap of 2.0 eV, which is about half of that of a diamond.. |
| 135. | Yukihiko Yamagata, Kazufumi Shingai, Alexander M. Grishin, Tomoaki Ikegami, Kenji Ebihara, Spectroscopic study of the YBa2Cu3O7-x ablation plasma plume Crossover from the "blast" to the "drag" regime, Thin Solid Films, 10.1016/S0040-6090(98)00388-5, 316, 1-2, 56-59, 1998.03, In order to clarify fundamental mechanism of pulsed laser deposition (PLD) process, Mach-Zehnder interferometry and laser scattering spectroscopy were applied to YBa2Cu3O7-x ablation plasma plume in atmospheric pressure. At the early stage ( |
| 136. | Shin Ichi Aoqui, Kenji Ebihara, Yukihiko Yamagata, Diamond-like carbon film preparation and surface coatings of oxide superconducting and ferroelectric films, Carbon, 10.1016/S0008-6223(98)00023-2, 36, 5-6, 591-594, 1998.01, Diamond-like carbon (DLC) films as well as amorphous carbon films are investigated as possible passivation and environment protection for YBa2Cu3O7-x (YBCO) oxide superconducting and Pb(ZrxTi1-x)O3 (PZT) ferroelectric thin films. The pulsed laser deposition (PLD) technique was employed to prepare the perovskite oxide films of YBCO and PZT. These film surfaces were coated by the DLC films prepared using the excimer laser ablation method. Optimum deposition condition of the PLD process for the YBCO, PZT and DLC was investigated. In the case of DLC coatings, a graphite target was ablated using a KrF excimer laser of 2-9 J cm-2 in 200-800 mTorr hydrogen ambient gas. An optical band gap of 2.0 eV was attained on room temperature substrate and high quality superconductivity of the DLC coated YBCO films was kept over 1 month. The PZT film encapsulated by the DLC layer showed no degradation due to aging over 30 days.. |
| 137. | H. Kurogi, Yukihiko Yamagata, K. Ebihara, N. Inoue, Preparation of PZT thin films on YBCO electrodes by KrF excimer laser ablation technique, Surface and Coatings Technology, 10.1016/S0257-8972(97)00663-4, 100-101, 1-3, 424-427, 1998.01, Pb(ZrxTi1-x)O3 (PZT) films have excellent ferroelectric, optical, piezoelectric, and pyroelectric properties. We prepared PZT thin films by the excimer laser ablation technique. A pulsed KrF excimer laser (Lambda Physik LPX305icc, pulse duration of 25 ns, λ = 248 nm, 850 mJ Max.) was used to ablate the bulk targets. We investigated the influence of bottom electrode materials on the characteristics of the PZT thin films prepared on Pt and YBCO underlayers. The X-ray diffraction (XRD) patterns showed that the PZT films prepared with a laser fluence of 2 J cm-2 on YBCO/MgO(100) substrate at a wide temperature range of 550-680 °C have a perovskite (00l) structure. At the same laser fluence, the PZT films prepared on Pt/MgO(100) substrate have a perovskite (00l) structure only at 650 °C . The polarization-electric field (P-E) characteristics and fatigue properties of PZT thin films were measured by the Sawyer-Tower circuit. The remnant polarization and coercive field have been found to be Pr =15 μCcm-2, 30 μC cm-2 and Ec = 200 kV cm-1, 100 kV cm-1 for Au/PZT/Pt/MgO and Au/PZT/YBCO/MgO correspondingly. The remnant polarization of Au/PZT/YBCO/MgO thin film was reduced to one-half after about 108 cycles of switching.. |
| 138. | Kenji Ebihara, Hiromitsu Kurogi, Yukihiko Yamagata, Tomoaki Ikegami, Alexander M. Grishin, Preparation of PZT/YBCO/YAlO heterostructure thin films by KrF excimer laser ablation, Quaternary International, 526, 193-198, 1998, The perovskite oxide YBa2Cu3O7-X (YBCO) and Pb(ZrXTi1-X)O3 (PZT) thin films have been deposited for superconducting-ferroelectric devices. KrF excimer laser ablation technique was used at the deposition conditions of 200-600 m Torr O2, 2-3 J/cm2 and 5-10 Hz operation frequency. Heterostructures of PZT-YBCO-YAlO3:Nd show the zero resistivity critical temperature of 82 K and excellent ferroelectric properties of remnant polarization 32 μC/cm2, coercive force of 80 kV/cm and dielectric constant 800. Cycling fatigue characteristics and leakage current are also discussed.. |
| 139. | A. M. Grishin, M. Yamazato, Yukihiko Yamagata, K. Ebihara, Structure and polarization in epitaxial ferroelectric PbZr0.52Ti0.48O3/YBa2Cu 3O7-x/Nd YAlO3 thin films, Applied Physics Letters, 10.1063/1.120824, 72, 5, 620-622, 1998, We fabricate epitaxial PbZr0.52Ti0.48O3/YBa2Cu 3O7-x submicron film ferroelectric/superconductor heterostructures on the single-crystal YAlO3+1%Nd2O3 substrate by the pulsed laser deposition technique. Frequency independent low loss tanδ=0.04 and dielectric constant of 950, high electric resistivity ρ (150kV/cm)=6×1011cm, remnant polarization of 32μC/cm2, no visible fatigue after 107 short bipolar pulses switching indicate excellent electrical performance of the new capacitor structure. The slight crystallite polar axis misalignment and depolarizing effect were found to be responsible for the shape of the apparent polarization loop. The only fitting parameter depolarizing coefficient N=2.37×10-4 gives the best fit between theory and experimental data and corresponds to prolate ellipsoidal shaped crystallites with the length-to-diameter ratio of 140.. |
| 140. | M. Yamazato, A. M. Grishin, Yukihiko Yamagata, T. Ikegami, K. Ebihara, Switching kinetics of pulsed laser deposited epitaxial PZT films, Quaternary International, 526, 187-191, 1998, We have fabricated epitaxial PbZr0.52Ti0.48O3 (PZT, 40 approximately 1200 nm)/YBa2Cu3O7-x (YBCO, 400 nm) film ferroelectric/superconductor heterostructures on the single-crystal neodymium doped yttrium monoaluminate [YAlO3+1%Nd2O3] and MgO substrates by KrF pulsed laser deposition technique. The dielectric constant of 950 and loss tangent δ of 0.04 have been found to be frequency independent in the range 100 Hz to 100 kHz while electric resistivity ρ (150 kV/cm) is of 6×1011 Ω·cm, remnant polarization and coercive field are 32 μC/cm2 and 43 kV/cm, respectively. Fast ferroelectric switching kinetics with characteristic switching time around 50 ns has been observed. Universal electric field and temperature dependencies of switching time as well as film thickness dependence of coercive electric field have been observed and correspond to ferroelectric needle-like domain switching.. |
| 141. | Yukihiko Yamagata, Kazufumi Shingai, Tomoaki Ikegami, Kenji Ebihara, Improvement in Switching Characteristics of HTS Power Electric Device Prepared by Pulsed Laser Deposition, IEEE Transactions on Applied Superconductivity, 7, 2 PART 2, 1447-1450, 1997.12, High quality YBCO film was prepared on the YSZ buffered Hastelloy substrate by PLD method with an effective in-situ anneal. The TC(zero) and the JC of the YBCO film on YSZ/Hastelloy is 83.4K and 6.6×103A/cm2 (at 77K), respectively. The phase transition between the superconducting state and the normal conducting slate of the film showed higher response due to the high thermal conductivity and the small thermal capacity than that of the YBCO film deposited on MgO substrate.. |
| 142. | Yukihiko Yamagata, Hiromitsu Kurogi, Keisuke Tsuchiya, Tomoaki Ikegami, Kenji Ebihara, Spectroscopic study of vapor-phase reactions in preparation of YBa2Cu3O7-x oxide thin film using pulsed laser deposition, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 36, 7 SUPPL. B, 4968-4970, 1997.07, Vapor-phase reactions in plasma plume during preparation of YBa2Cu3O7-x superconducting thin film are investigated using optical emission spectroscopy. Argon/oxygen gas mixtures of various ratios are used as ambient to study the formation of diatomic oxides. Most of YO and some of BaO molecules are formed in the vapor, while CuO molecules are not formed in the vapor but only ejected from the target. To obtain high-quality oxide thin films, fluxes of the oxide molecules, atoms and ions reaching a substrate, which are dependent on laser energy density, argon mixture ratio and total pressure, should be controlled.. |
| 143. | Yukihiko Yamagata, Hiromitsu Kurogi, Tomoaki Ikegami, Kenji Ebihara, Plasma phase oxidation during preparation of oxide superconducting and ferroelectric thin films using pulsed laser deposition, Applied Surface Science, 10.1016/S0169-4332(96)00642-3, 109-110, 611-615, 1997.01, Plasma phase oxidation was investigated during preparation of Y-Ba-Cu-O (YBCO) superconducting and Pb-Zr-Ti-O (PZT) ferroelectric thin films using KrF pulsed laser deposition. The YBCO and PZT plasma plumes were produced at a laser fluence of 0.1 to 6 J/cm2, a mixture ambient of oxygen and argon and a pressure range of 10-6-1 Torr. In the YBCO ablation, YO and BaO molecules are formed in the ablation plasma with different reactivities, while most of the CuO molecules are ejected from the target. In the PZT film preparation, TiO molecules are generated in the plasma phase. Plasma phase oxidation affects strongly the characteristics of oxide superconducting and ferroelectric thin films.. |
| 144. | K. Ebihara, K. Shingai, Yukihiko Yamagata, T. Ikegami, A. M. Grishin, Y-Ba-Cu-O thick film preparation using multistep KrF excimer laser deposition, Journal of Alloys and Compounds, 10.1016/S0925-8388(96)02807-1, 251, 1-2, 228-231, 1997.01, Thick films of high-temperature superconductors (HTSC) have attracted much attention to a number of current-carrying applications such as current leads, interconnects, current limiters and cryotron-type switchs. As the film thickness of HTSC films is increased using the conventional method of pulsed laser deposition, the surface morphology Is degraded during the film deposition. This structural transition results in decreasing the critical current density with the film thickness. Here, a multistep deposition technique in the KrF excimer laser ablation is used to prepare Y-Ba-Cu-O thick films. The high-quality Y-Ba-Cu-O superconducting films of thickness of a few mm were formed by optimizing the processing conditions from the bottom to the surface of the film. The initial ultrathin layer of a few nm was prepared at the low repetition rate of 1 Hz at laser fluence 3 J cm-2. Then, various repetition rates at the fluence 2 J cm-2 were chosen for deposition of the intermediate layer and the surface layer, both with thicknesses of about 1 μm. It is shown that surface morphology and vertical growth are significantly dominated by the initial layer structure and the following deposition conditions. The thick films with high Tc(zero) 89 K were obtained when the surface layer was prepared at a lower repetition rate under lower process temperature. The three step procedure prepared the superconducting thick films with the critical current density of 1.2×106 A cm-2 (at 5 K).. |
| 145. | Yukihiko Yamagata, Hiromitsu Kurogi, Tomoaki Ikegami, Kenji Ebihara, Plasma phase oxidation during preparation of oxide superconducting and ferroelectric thin films using pulsed laser deposition, Proceedings of the 1996 E-MRS Spring Conference Symposium H on Laser Processing of Surfaces and Thin Films, 611-615, 1997.01, Plasma phase oxidation was investigated during preparation of Y-Ba-Cu-O (YBCO) superconducting and Pb-Zr-Ti-O (PZT) ferroelectric thin films using KrF pulsed laser deposition. The YBCO and PZT plasma plumes were produced at a laser fluence of 0.1 to 6 J/cm2, a mixture ambient of oxygen and argon and a pressure range of 10-6-1Torr. In the YBCO ablation, YO and BaO molecules are formed in the ablation plasma with different reactivities, while most of the CuO molecules are ejected from the target. In the PZT film preparation, TiO molecules are generated in the plasma phase. Plasma phase oxidation affects strongly the characteristics of oxide superconducting and ferroelectric thin films.. |
| 146. | Hiromitsu Kurogi, Yukihiko Yamagata, Tomoaki Ikegami, Kenji Ebihara, Yin Tong Bok, Preparation of PbZrxTi1-xO3 thin films by KrF excimer laser ablation technique, Quaternary International, 433, 237-242, 1996, A pulsed KrF excimer laser was used to ablate PZT thin films. The composition, crystallization, and ferroelectric properties of the PZT thin films prepared under various conditions were investigated. X ray diffraction (XRD) patterns showed that the PZT thin films prepared on MgO(100) substrates had a perovskite - pyrochlore mixed structure. The condition of 100 mTorr oxygen pressure provides high quality perovskite films. It was also found that the stoichiometric condition of the deposited films was obtained in ambient oxygen of 100 to approximately 400 mTorr. The ferroelectric properties of the Pt/PZT/Pt/MgO structure were also studied. The capacitance-voltage characteristics and the corresponding hysteresis loop of the dielectric-electric field curve are discussed.. |
| 147. | Tomoaki Ikegami, Kazufumi Shingai, Yukihiko Yamagata, Kenji Ebihara, Large Current and Low Voltage Switching Devices Using HTS Thin Film, IEEE Transactions on Applied Superconductivity, 10.1109/77.402519, 5, 2, 246-249, 1995.01, A high Temperature Superconducting (HTS) thin film has a potential to control large currents using its transition between a superconducting state and a normal conducting state. In this paper an equivalent circuit model of a HTS thin film is presented to design a power conditioning circuit as an inverter which can handle large currents at voltages less than IV. Device model parameters of a HTS thin film were determined by comparing quenching characteristics calculated by a circuit simulation program (PSpice) with those measured experimentally. A temporal behavior of resistance of the HTS thin film quenched by a self-current which was simulated using the model were compared with experimental results. An inverter circuit using the HTS thin film switched thermally is designed and the characteristic of a switching operation with a photovoltaic cell is also shown.. |
| 148. | Yukihiko Yamagata, Chung Seog Choi, Tomoyuki Fujishima, Tomoaki Ikegami, Kenji Ebihara, Yoshiaki Suda, Orientation Control of YBaCuO Film on Flexible Metallic Substrates with Buffer Layers Using Pulsed Laser Deposition, IEEE Transactions on Applied Superconductivity, 10.1109/77.402961, 5, 2, 1932-1935, 1995.01, A preparation of YBaCuO thin film on a flexible metallic substrate with YSZ buffer layer by the KrF pulsed laser deposition (PLD) was investigated. The orientation of the YBaCuO/YSZ/Metal film was controlled by the YSZ deposition conditions. A critical temperature and a critical current density of the YBaCuO/YSZ film were 81.8K, 1.2x103A/cm2 (at 77.3K) for Hastelloy substrate, and 79.2K, 102A/cm2 for Inconel substrate, respectively. Those low values resulted in their polycrystalline structures.. |
| 149. | M. D. Bowden, T. Nakamura, K. Muraoka, Yukihiko Yamagata, B. W. James, M. Maeda, Measurements of the cathode sheath in a magnetron sputtering discharge using laser induced fluorescence, Journal of Applied Physics, 10.1063/1.352925, 73, 8, 3664-3667, 1993.12, Magnetron discharges are widely used as sputtering sources for thin film deposition. Despite the importance of the sheath region where the electric field can be very high, there have been few experimental investigations of this region in magnetron plasmas. We report values of the sheath thickness deduced from measurements of the electric field distribution using laser spectroscopy. With this technique, a transition which is normally forbidden becomes in the presence of an electric field partially allowed so that laser induced fluorescence on this transition can be used as a measure of the electric field. It was found that the sheath thickness was approximately equal to the maximum displacement, in the absence of collisions, of a secondary electron from the cathode surface.. |
| 150. | Tomoaki Ikegami, Yukihiko Yamagata, Kenji Ebihara, Hajime Nakajima, Application of high-tc superconductor to current limiting devices, IEEE Transactions on Applied Superconductivity, 10.1109/77.233769, 3, 1, 566-569, 1993.01, Resistive characteristics of YBa2Cu3O7-x superconducting thin film quenched by a current were investigated. The thin films were prepared on MgO substrates by the laser ablation method and currents of different wave forms were fed to it for few tens milliseconds in a liquid nitrogen to measure a temporal resistance. A resistance appeared quickly above a critical current then increased to about 8Q within few milliseconds which depended on an input power to the film. To investigate characterisites of the current-quenched superconducting film, a 1-dimensional heat transfer equation was numerically solved using a finite-difference method. Comparing these experimental and numerical results it was found that non-uniformities in a current density or a temperature may exist in the quenching thin film.. |
| 151. | W. Z. Park, T. Eguchi, C. Honda, K. Muraoka, Yukihiko Yamagata, B. W. James, M. Maeda, M. Akazaki, Investigation of the thermalization of sputtered atoms in a magnetron discharge using laser-induced fluorescence, Applied Physics Letters, 10.1063/1.104827, 58, 22, 2564-2566, 1991.12, The thermalization of sputtered atoms in a magnetron discharge was investigated using laser-induced fluorescence. The results clearly indicated for the first time that the velocity distribution agrees well with the Thompson formula [M. W. Thompson, Philos. Mag. 18, 377 (1968)] for d/λ≪1, while a thermalized component becomes appreciable for d/λ≳1, where d is the distance from the cathode surface and λ is the mean free path of sputtered atoms for collisions with filling gas atoms.. |
| 152. | Yukihiko Yamagata, Yasuhiko Kawano, Katsunori Muraoka, Mitsuo Maeda, Masanori Akazak, In-situ calibration for electric field measurements in glow-discharge plasmas by laser-induced fluorescence using the optogalvanic technique, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.1143/JJAP.30.166, 30, 1, 166-170, 1991, We proposed and performed an in-situ calibration of electric field determination in glow-discharge plasmas based on the Stark effect, to relate ratios of laser-induced fluorescence (LIF) intensities (forbidden/allowed) with electric fields E, where accurate E values were measured by the laser optogalvanic (LOG) method. The results were compared with Bell Lab Group static calibration, and yielded 30% lower E value at a given fluorescence intensity. It is discussed, by the aid of solutions of rate equations for the LIF processes, that the present calibration is more accurate at higher electric field (E> 100 V/mm) than that obtained by extrapolation of Bell Lab Group results at lower field (£’ |
| 153. | Yukihiko Yamagata, Kiyoyuki Suenaga, Katsunori Muraoka, Mitsuo Maeda, Masanori Akazaki, Improvement in detection limit of electric field measurement using optogalvanic signals by laser excited rydberg atoms, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.1143/JJAP.28.565, 28, 3 R, 565-566, 1989, Optogalvanic signals, caused by laser-excited Rydberg atoms, were measured to estimate the electric field in a DC glow discharge in helium. With a careful analysis of the various factors limiting the detection limit and an experiment to check the analysis, the detection limit of an electric field of 21.5 V/mm was obtained which was limited by the laser spectral width.. |
| 154. | Katsunori Muraoka, Kiyoyuki Suenaga, Kenji Morita, Yukihiko Yamagata, Hee Je Kim, Chikahisa Honda, Mitsuo Maeda, Masanori Akazaki, Surface binding energy of nickel measured by laser fluorescence spectroscopy, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.1143/JJAP.28.561, 28, 3 R, 561-562, 1989, The surface binding energy of nickel was estimated from the measured velocity-distribution function of sputtered nickel atoms by rapid-frequency-scan laser spectroscopy, yielding 1.2±0.5 eV, which was about one third of the sublimation energy of nickel. The results were interpreted as the formation at the surface of a carbide phase which weakened the binding of atoms, compared with that in pure nickel.. |
| 155. | Yoshinobu Matsuda, Kouji Yamaguchi, Kiyoyuki Suenaga, Yukihiko Yamagata, Chikahisa Honda, Mitsuo Maeda, Yasunori Yamamura, Katsunori Yamamura, Masanori Akazaki, Measurement of preferential sputtering of iron-oxides using laser fluorescence spectroscopy, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.1143/JJAP.27.L2022, 27, 11 A, L2022-L2024, 1988, Laser fluorescence spectroscopy was used to obtain the velocity-distribution function of sputtered iron from iron oxides, and the fitting of the obtained profiles with the Thompson formula yielded the preferential sputtering of oxygen from iron oxides quantitatively.. |
| 156. | Kenji Ebihara, Seiji Kanazawa, Yukihiko Yamagata, Sadao Maeda, Pulsed electromagnetic inductive plasma-enhanced chemical-vapor deposition of amorphous carbon films, Journal of Applied Physics, 10.1063/1.341816, 64, 3, 1440-1445, 1988, A pulsed electromagnetic inductive methane discharge process was developed to form amorphous carbon thin films. In order to estimate the methane plasma state in the pulsed plasma process, the time-resolved excitation temperature was measured by means of relative spectral intensity method. At the high electromagnetic compression phase the pulsed plasma has an excitation temperature of the same order (20 000-50 000 K) as in the conventional rf glow discharges. The deposited thin films are transparent in the IR and adhere well to room-temperature substrates. The optical energy gap and the electrical conductivity of the amorphous carbon films are investigated and compared with the amorphous carbon films prepared with rf glow plasma chemical vapor deposition. The optical gap is observed to decrease from 1.26 to 1.14 eV as the deposition temperature and the charging voltage increase. It is shown that dynamic pulsed plasma flows affect the phase transition from a diamondlike structure to a graphitic structure.. |
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