強磁性Fe3Si/半導体FeSi2人工格子をベースとした新規スピントロニクス素子の創製
キーワード：Fe-Si、スピントロニクス、CPP、リソグラフィー
2011.04.

超ナノ微結晶ダイヤモンド/水素化アモルファスカーボン混相(UNCD/a-C:H)膜のフォトダイオードへの応用
キーワード：超ナノ微結晶ダイヤモンド、UNCD、フォトダイオード，太陽電池
2011.04.

立方晶β-AlNの創製と物性の解明
キーワード：準安定相、AlN、物理気相成長法、zincblende構造
2005.04.

成膜装置の開発を含めた同軸型アークプラズマ蒸着法による超ナノ微結晶ダイヤモンド薄膜の作製とその工業的応用の検討
キーワード：超ナノ微結晶ダイヤモンド、アークプラズマ
2005.04.

レーザーアブレーション法によるダイヤモンドおよびナノ微結晶ダイヤモンド薄膜の低温成長
キーワード：超ナノ微結晶ダイヤモンド、UNCD、レーザーアブレーション、低温成長
2000.04～2006.03.

環境考慮型シリサイド半導体の作製とその電子デバイスへの応用に関する研究
キーワード：ベータ鉄シリサイド、ナノ微結晶、アブレーション、スパッタリング、薄膜、結晶成長、エピタキシャル、光特性、電気特性
1999.04.

（半導体）／（強磁性金属）人工格子薄膜に関する研究
キーワード：半導体、強磁性体、Fe-Si、スピントロニクス、MR、強磁性層間結合、人工格子、超格子
2001.04～2011.03.

物理気相成長法による水素フリーダイヤモンド状炭素膜の作製と硬質皮膜への応用
キーワード：DLC、レーザーアブレーション、ダイヤモンド状炭素、硬度
1996.04～2003.03.

ナノカーボンによる新規太陽電池の創製
2011.10～2014.03, 代表者：吉武剛, 九州大学, 九州大学
直径数nmのダイヤモンド微結晶を水素化アモルファスカーボンが取り囲む構造を持つ超ナノ微結晶ダイヤモンド/水素化アモルファスカーボン混相膜は，膜中に多量のダイヤモンド結晶の界面が内在し，それに起因すると考えられる大きな光吸収を可視域で示す．今までの研究で，これに対応した明確な光電流を確認している．JST ALCAのもと，この光吸収で発生する光電流を太陽電池に応用することを目指す．.

主要著書

1.	吉武 剛, 3.4節パルスレーザ堆積法&3.5節スパッタリング成膜法 in シリサイド系半導体の科学と技術: 資源・環境時代の新しい半導体と関連物質（前田佳均編）, 裳華房, pp. 93-112, 2014.10.
2.	Mahmoud Shaban and Tsuyoshi Yoshitake, n-Type β-FeSi2/p-type Si near-infrared photodiodes prepared by facing-targets direct-current sputtering, InTech Open Access Publisher, in Advances in Photodiodes (InTech, 2010) Chap. 1., 2010.12.
3.	監修：杉岡幸次、矢部明、著者３５名, レーザーマイクロ・ナノプロセッシング, シーエムシー出版, 担当分： 第III偏第1章5節ダイヤモンド・ダイヤモンド状炭素 145〜160頁, 2004.11.

主要原著論文

1.	Sreenath Mylo Valappil, Abdelrahman Zkria, Shinya Ohmagari, Hiroshi Naragino, Hiromitsu Kato, Tsuyoshi Yoshitake, Corrosion-resistive and Low Specific Contact Resistance Ohmic Contacts to Semiconducting Diamonds Using Nanocarbon electrodes, Phys. Status Solidi A, https://doi.org/10.1002/pssa.202200627, Volume220, Issue3 (2023) 2200627, 2023.02.
2.	Lama Osman, Ali M. Ali, Abdelrahman Zkria, Hiroshi Naragino, Tsuyoshi Yoshitake, Adhesion of Nanodiamond composite films on Ti substrates at Room Temperature via hybrid ion etching gun and coaxial arc plasma deposition, Applied Physics Express, https://iopscience.iop.org/article/10.35848/1882-0786/ac99b6, Vol. 15, Number 11 (2022) 115004, 2022.10.
3.	Sreenath Mylo Valappil, Shinya Ohmagari, Abdelrahman Zkria, Phongsaphak Sittimart, Eslam Abubakr, Hiromitsu Kato, Tsuyoshi Yoshitake, Nanocarbon electrodes fabricated by coaxial arc plasma deposition for phosphorus-doped diamond electronics application, AIP Advances , https://doi.org/10.1063/5.0093470, 12, 085007 (2022), 2022.08.
4.	Eslam Abubakr, Shinya Ohmagari, Abdelrahman Zkria, Hiroshi Ikenoue, Julien Pernot, and Tsuyoshi Yoshitake, Formation of p-n+ diamond homojunctions by shallow doping of phosphorus through liquid emersion excimer laser irradiation, Materials Research Letters, https://doi.org/10.1080/21663831.2022.2083457, Vol. 10, Issue 10 (2022) pp. 666-674, 2022.06.
5.	Eslam Abubakr, Shinya Ohmagari, Abdelrahman Zkria, Hiroshi Ikenoue, Julien Pernot, Tsuyoshi Yoshitake, Formation of p-n+ diamond homojunctions by shallow doping of phosphorus through liquid emersion excimer laser irradiation, Materials Research Letters, https://doi.org/10.1080/21663831.2022.2083457, Vol. 10, Issue 10 (2022) pp. 666-674, 2022.06.
6.	Eslam Abubak, ShinyaOhmagar, Abdelrahman Zkria, Hiroshi Ikenoue, and Tsuyoshi Yoshitake, Laser-induced novel ohmic contact formation for effective charge collection in diamond detectors, Materials Science in Semiconductor Processing, https://doi.org/10.1016/j.mssp.2021.106370, Vol. 139 (2022) 106370, 2022.03, In this study, we employed an authentic process for the device fabrication of diamond detectors, wherein thin, highly conductive surface layers were processed in bulk diamond substrate using a nanosecond-pulsed excimer laser with liquid-immersion irradiation. The incorporation of high-concentration phosphorus dopants at 40 nm under the irradiated surface characterized the irradiated areas with much lower electrical resistivity, which was adequate for demonstrating ohmic contacts even with the tungsten probe heads at room temperature. In particular, a low activation energy (
7.	Ali M. Ali, Mohamed Egiza, Koki Murasawa, Hiroaki Sugita, Tanja Deckert-Gaudig, Volker Deckert, Tsuyoshi Yoshitake, Effects of substrate temperature and intermediate layer on adhesion, structural and mechanical properties of coaxial arc plasma deposition grown nanodiamond composite films on Si substrates , Surface & Coatings Technology, https://doi.org/10.1016/j.surfcoat.2021.127185, Vol. 417, 127185, 2021.06, Low-temperature fabrication of nanodiamond films on untreated silicon substrates, which are preferred sub-strates and widely employed in industry, can extend nanodiamond film applications, for instance in biosensing and miniaturization technologies. For its realization, the weak adhesion of nanodiamond films on silicon sub-strates due to insufficient atomic interdiffusion at the interfaces is a serious issue that needs to be overcome. In the present study, coaxial arc plasma deposition (CAPD) grown nanodiamond films were fabricated at low temperatures on silicon substrates. The effects of the substrate temperature, which is an important parameter in the CAPD nanodiamond film growth process, were structurally and physically investigated. It was found that the films softened with increasing substrate temperature and atomic interdiffusions at interfaces between the films and substrates were activated, which resulted in the formation of SiC at the interfaces. On the other hand, the films fabricated directly on silicon at room temperature were exfoliated due to the poor adhesion and high re-sidual stress. Consequently, intermediate layers that were fabricated at elevated substrate temperatures were employed to improve the adhesion strength of nanodiamond films on silicon substrates. This way, the atomic interdiffusion at the interfaces could be promoted and the residual stress in the films was relieved. In the second stage, the films were fabricated on the intermediate layers at different temperatures. It has shown that the top layer films fabricated at low temperature gained distinctive mechanical and structural properties. By applying this strategy, several micrometres of hard nanodiamond films can be fabricated on Si substrates without easily being peeled off..
8.	Eslam Abubakr, Abdelrahman Zkria, Shinya Ohmagari, Yu̅ki Katamune, Hiroshi Ikenoue, Tsuyoshi Yoshitake, Laser-Induced Phosphorus-Doped Conductive Layer Formation on Single-crystal Diamond Surfaces, ACS Applied Materials & Interfaces, DOI: 10.1021/acsami.0c18435, 12, pp. 57619-57626, 2020.12, A laser-induced doping method was employed to incorporate phosphorus into an insulating monocrystalline diamond at ambient temperature and pressure conditions. Pulsed laser beams with nanosecond duration (20 ns) were irradiated on the diamond substrate immersed in a phosphoric acid liquid, in turns, and a thin conductive layer was formed on its surface. Phosphorus incorporation in the depth range of 40−50 nm below the irradiated surface was confirmed by secondary ion mass spectroscopy (SIMS). Electrically, the irradiated areas exhibited ohmic contacts even with tungsten prober heads at room temperature, where the electrical resistivity of irradiated areas was greatly decreased compared to the original surface. The temperature dependence of the electrical conductivity implies that the surface layer is semiconducting with activation energies ranging between 0.2 eV and 54 meV depending on irradiation conditions. Since after laser treatment no carbon or graphitic phases other than diamond is found (the D and G Raman peaks are barely observed), the incorporation of phosphorus is the main origin of the enhanced conductivity. It was demonstrated that the proposed technique is applicable to diamond as a new ex situ doping method for introducing impurities into a solid in a precise and well-controlled manner, especially with electronic technology targeting of smaller devices and shallower junctions..
9.	Ali M. Ali, Mohamed Egiza, Koki Murasawa, Hiroaki Sugita, Tanja Deckert-Gaudig, Volker Deckert, and Tsuyoshi Yoshitake, Influence of adhesion intermediate layers on the stability of nanodiamond composite films deposited on Si substrates by coaxial arc plasma, Applied Physics Express, https://doi.org/10.35848/1882-0786/ab91d1, Vol. 13, No. 6 (2020) 065506, 2020.06, Raman spectroscopic studies on nanodiamond composite (NDC) films, comprising nano-sized diamond grains and an amorphous carbon (a-C) matrix, deposited by coaxial arc plasma deposition are challenging because the scattering of the nano-sized diamond grains competes with the strong signal of the a-C matrix. To unravel the nanocomposite structure of NDC films, both far- and near-field Raman spectroscopy were employed. Based on the comparison of visible and ultraviolet far-field Raman data, component spectra based on either nanodiamond or a-C were estimated by a peak-decomposition procedure based on band fitting. Near-field optical resolution achieved via tip-enhanced Raman spectroscopy reveals sharper peaks of both the nanodiamond and the amorphous carbon than the far-field spectra. Consequently, the peak-decomposition procedure is not required, which evidently indicates the effective detection of nanodiamond grains embedded in a-C matrices and is a direct result of the high spatial resolution that limits the number of probed grains. The size of the nanocrystals could additionally be estimated from the profile and position of a diamond peak. This work demonstrates that tip-enhanced Raman spectroscopy is a powerful nondestructive method for nanodiamond composite films, which allows direct access to parameters hitherto only available via average data..
10.	Abdelrahman Zkria, Mohamed Egiza, Ariful Haque, Eslam Abubakr, Jagdish Narayan, Tsuyoshi Yoshitake, Monitoring laser-induced structural evolution of hydrogenated nanodiamond composite films prepared by coaxial arc plasma deposition, Applied Physics Express, https://iopscience.iop.org/article/10.35848/1882-0786/abb871, Vol. 13, No. 10, 105503, 2020.06.
11.	M. Ali Ali, Tanja Deckert-Gaudig, Mohamed Egiza, Volker Deckert, Tsuyoshi Yoshitake, Near- And far-field Raman spectroscopic studies of nanodiamond composite films deposited by coaxial arc plasma, Applied Physics Letters, 10.1063/1.5142198, 116, 4, 2020.01, [URL], Raman spectroscopic studies on nanodiamond composite (NDC) films, comprising nano-sized diamond grains and an amorphous carbon (a-C) matrix, deposited by coaxial arc plasma deposition are challenging because the scattering of the nano-sized diamond grains competes with the strong signal of the a-C matrix. To unravel the nanocomposite structure of NDC films, both far- and near-field Raman spectroscopy were employed. Based on the comparison of visible and ultraviolet far-field Raman data, component spectra based on either nanodiamond or a-C were estimated by a peak-decomposition procedure based on band fitting. Near-field optical resolution achieved via tip-enhanced Raman spectroscopy reveals sharper peaks of both the nanodiamond and the amorphous carbon than the far-field spectra. Consequently, the peak-decomposition procedure is not required, which evidently indicates the effective detection of nanodiamond grains embedded in a-C matrices and is a direct result of the high spatial resolution that limits the number of probed grains. The size of the nanocrystals could additionally be estimated from the profile and position of a diamond peak. This work demonstrates that tip-enhanced Raman spectroscopy is a powerful nondestructive method for nanodiamond composite films, which allows direct access to parameters hitherto only available via average data..
12.	Mohamed Egiza, Kouki Murasawa, Ali M. Ali, Yasuo Fukui, Hidenobu Gonda, and Masatoshi Sakurai, and Tsuyoshi Yoshitake, Enhanced hardness of nanocarbon films deposited on cemented tungsten carbide substrates by coaxial arc plasma deposition owing to employing silicon-doped graphite targets, Japanese Journal of Applied Physics, https://iopscience.iop.org/article/10.7567/1347-4065/ab289f, 58, 7, 075507. , 2019.07, .
13.	Ali M. Ali, Mohamed Egiza, Koki Murasawa, Yasuo Fukui, Hidenobu Gonda, Masatoshi Sakurai, Tsuyoshi Yoshitake, Negative bias effects on deposition and mechanical properties of ultrananocrystalline diamond/amorphous carbon composite films deposited on cemented carbide substrates by coaxial arc plasma, Diamond and Related Materials, 10.1016/j.diamond.2019.04.031, 96, 67-73, 2019.06, [URL], Ultrananocrystalline diamond/amorphous carbon composite (UNCD/a-C) films were deposited on negatively biased cemented carbide (WC-Co) substrates by coaxial arc plasma deposition. The deposition rate is increased to be 0.9 nm/s, which is approximately 3 times larger than that of films deposited under no bias condition. In addition, the critical load in scratch tests was enhanced to be 31 N, which is 4 times more than that of the no bias films. On the other hand, the hardness was slightly degraded by employing the negative bias. From electrical diagnostics of the bias application, it was found that the negative bias is immediately compensated by the arrival of highly-dense positive carbon ions at the substrate and the substrate is weakly positively charged after the compensation. This might be the main reason for the degraded hardness by the bias application, Since the positive bias deaccelerate carbon ions, which facilities the formation of sp2 bonds..
14.	Eslam Abubakr, Abdelrahman Zkria, Yūki Katamune, Shinya Ohmagari, Kaname Imokawa, Hiroshi Ikenoue, Tsuyoshi Yoshitake, Formation of low resistivity layers on singlecrystalline diamond by excimer laser irradiation, Diamond and Related Materials, 10.1016/j.diamond.2019.04.013, 95, 166-173, 2019.05, [URL], A singlecrystalline diamond (100)(Ib) plate immersed in 2% boric acid was irradiated by 193-nm ArF excimer laser beams for the formation of conductive layers on the surface of an insulating diamond substrate. From current-voltage measurements of the irradiated areas, it was confirmed that semiconducting layers with high conductivities are formed on the diamond surface. It was possible to form ohmic contacts by directly touching tungsten probes with the layer surface. Since Raman spectra exhibited only peaks due to diamond and no peaks due to amorphous carbon, the drastically enhanced conductivity is not attributed to amorphous carbon formation but due to the incorporation of boron atoms into the diamond subsurface from the dopant acid. Secondary ion mass spectrometric depth profile showed the incorporation of boron atoms up to 40 nm depths from the surface. From cathodoluminescence measurements at low temperatures, it was difficult to detect clear peaks for the substitutional incorporation of boron atoms into diamond lattices, which could be attributed to the small thickness of the doped layer for detection. The proposed technique is a new potential method for shallow doping and formation of conductive layers on singlecrystalline diamond surfaces..
15.	Satoshi Takeichi, Takashi Nishiyama, Mitsuru Tabara, Shuichi Kawawaki, Masamichi Kohno, Koji Takahashi, Tsuyoshi Yoshitake, Hydrogenation effects on thermal conductivity of ultrananocrystalline diamond/amorphous carbon com-posite films prepared by coaxial arc plasma deposition, Appl. Phys. Express, https://doi.org/10.7567/APEX.11.065101, Vol. 11, No. 6 (2018) 065101, 2018.06.
16.	Abdelrahman Zkria, Tsuyoshi Yoshitake, Temperature-dependent current-voltage characteristics and ultraviolet light detection of heterojunction diodes comprising n-type ultrananocrystalline diamond/hydrogenated amorphous carbon composite films and p-type silicon substrates, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.7567/JJAP.56.07KD04, 56, 7, 2017.07, [URL], Heterojunction diodes comprising poorly (1 at. %) nitrogen-doped n-type ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/a-C:H) films and p-type Si substrates were prepared in nitrogen and hydrogen mixed gas atmosphere by coaxial arc plasma deposition. Dark current density-voltage (J-V) characteristics were studied in the temperature range of 200-400 K, in order to investigate the current transport mechanism through the fabricated heterojunctions. The temperature dependence of the ideality factor and reverse saturation current reveals that carrier transport predominantly occurs in the generation-recombination mechanism and, at low temperatures, it accompanies tunneling via weak traps. The heterojunctions surely exhibited photodetection for 254nm ultraviolet light illumination. It is expected that photocarriers will be generated at UNCD grains and transported through an a-C:H matrix..
17.	Takanori Hanada, Shinya Ohmagari, Abdelrahman Zkria, Nathaporn Promros, Tsuyoshi Yoshitake, Photodetection Characteristics of Heterojunctions Comprising p-Type Ultrananocrystalline Diamond/Hydrogenated Amorphous Carbon Composite Films and n-Type Si Substrates at Low Temperatures, Journal of Nanoelectronics and Nanotechnology, DOI: https://doi.org/10.1166/jnn.2017.14104, Vol. 17, No. 5, pp. 3348-3351, 2017.05.
18.	Abdelrahman Zkria, Hiroki Gima, Tsuyoshi Yoshitake, Application of nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous carbon composite films for ultraviolet detection, Appl. Phys. A, DOI 10.1007/s00339-017-0798-4, Vol. 123, issue 581, 167 (6 pages), 2017.02.
19.	Hiroki Gima, Abdelrahman Zkria, Yuki Katamune, Ryota Ohtani, Satoshi Koizumi, Tsuyoshi Yoshitake, Chemical bonding structural analysis of nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous carbon composite films prepared by coaxial arc plasma deposition, Applied Physics Express, 10.7567/APEX.10.015801, 10, 1, 2017.01, [URL], Nitrogen-doped ultra-nanocrystalline diamond/hydrogenated amorphous carbon composite films prepared in hydrogen and nitrogen mixed-gas atmospheres by coaxial arc plasma deposition with graphite targets were studied electrically and chemical-bonding-structurally. The electrical conductivity was increased by nitrogen doping, accompanied by the production of n-type conduction. From X-ray photoemission, near-edge X-ray absorption fine-structure, hydrogen forward-scattering, and Fourier transform infrared spectral results, it is expected that hydrogen atoms that terminate diamond grain boundaries will be partially replaced by nitrogen atoms and, consequently, φ C-N and C=N bonds that easily generate free electrons will be formed at grain boundaries..
20.	Abdelrahman Zkria, Mahmoud Shaban, Takanori Hanada, Nathaporn Promros, Tsuyoshi Yoshitake, Current transport mechanisms in n-type ultrananocrystalline diamond/p-type Si heterojunctions, Journal of Nanoscience and Nanotechnology, 10.1166/jnn.2016.13663, 16, 12, 12749-12753, 2016.12, [URL], Nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/a-C:H) films were deposited on p-type Si substrates by coaxial arc plasma deposition. The deposited films possessed n-type conduction, and evidently formed pn heterojunctions with p-type Si substrates. The heterojunction devices showed typical rectification properties similar to those observed for conventional abrupt pn heterojunctions. The conduction mechanisms that govern current transport in these devices were analyzed using dark current-voltage measurements in the temperature range from 300 K to 80 K. The results revealed that a trap-assisted multi-step tunneling process is a dominant mechanism at lower temperatures and low forward bias. At least two defect levels with activation energies of 42 and 24 meV appear to activate this process. At moderate forward bias, the current followed a power-law dependence, attributable to a space-charge-limited current. This junction behavior might be owing to a large number of grain boundaries in the UNCD/a-C:H film that provide active centers for carrier recombination-tunneling processes at the junction interface..
21.	Abdelrahman Zkria, Yuki Katamune, Tsuyoshi Yoshitake, Effects of Nitrogen doping on the electrical conductivity and optical absorption of ultrananocrystalline diamond/hydrogenated amorphous carbon films prepared by coaxial arc plasma dep, Jpn. J. Appl. Phys., http://doi.org/10.7567/JJAP.55.07LE01, Vol. 55, No. 7S2 (2016) 07LE01, 2016.07.
22.	Nathaporn Promros, Ryuji Baba, Motoki Takahara, Tarek M. Mostafa, Phongsaphak Sittimart, Mahmoud Shaban, Tsuyoshi Yoshitake, Epitaxial Growth of beta-FeSi2 Thin Films on Si(111) Substrates by Radio Frequency Magnetron Sputtering and Their Application to Near-Infrared Photodetection, Jpn. J. Appl. Phys., http://doi.org/10.7567/JJAP.55.06HC03, Vol. 55, No. 6S2, 06HC03, 2016.06.
23.	Hiroshi Naragino, Mohamed Egiza, Aki Tominaga, Kouki Murasawa, Hidenobu Gonda, Masatoshi Sakurai, Tsuyoshi Yoshitake, Room-temperature hard coating of ultrananocrystalline diamond/nonhydrogenated amorphous carbon composite films on tungsten carbide by coaxial arc plasma deposition, Jpn. J. Appl. Phys. (Rapid Communication), http://doi.org/10.7567/JJAP.55.030302, Vol. 55, No. 3, 030302., 2016.01.
24.	Takeshi Hara, Kenji Hanada, Tsuyoshi Yoshitake, Detection Methods of Diamond Diffraction Peaks in Ultrananocrystalline diamond?Amorphous Carbon Composite Films by X-ray Diffraction Measurement with Semiconductor Counter Detector, Jpn. J. Appl. Phys, to be published, 2015.11.
25.	Yūki Katamune, Satoshi Takeichi, Shinya Ohmagari, Tsuyoshi Yoshitake, Hydrogenation effects on carrier transport in boron-doped ultrananocrystalline diamond/amorphous carbon films prepared by coaxial arc plasma deposition, J. Vac. Sci. Tech. A, http://dx.doi.org/10.1116/1.4931062, Vol. 6, Issue 6 (2015) 061514., 2015.09.
26.	Abdelrahman Zkria, Hiroki Gima, Mahmoud Shaban, Tsuyoshi Yoshitake, Electrical Characteristics of Nitrogen-Doped Ultrananocrystalline Diamond/Hydrogenated Amorphous Carbon Composite Films Prepared by Coaxial Arc Plasma Deposition , Appl. Phys. Express, doi:10.7567/APEX.8.095101, Vol. 8, No. 9 (2015) 095101, 2015.09, Nitrogen-incorporated ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/a-C:H) films were synthesized in nitrogen and hydrogen mixed gas atmospheres by coaxial arc plasma deposition. The temperature dependence of electrical resistivity implies that carriers are transported in hopping conduction. Heterojunctions comprising 3 at.% nitrogen-doped films and p-Si substrates exhibited a typical rectifying action. The expansion of a depletion region into the film side was confirmed from the capacitance–voltage characteristics, and the built-in potential and carrier concentration were estimated to be 0.51 eV and 7.5 ' 1016cm%3, respectively. It was experimentally demonstrated that nitrogen-doped UNCD/a-C:H is applicable as an n-type semiconductor..
27.	Hiroshi Naragino, Aki Tominaga, Kenji Hanada, Tsuyoshi Yoshitake, A synthesis method of ultrananocrystalline diamond in powder employing a coaxial arc plasma gun, Appl. Phys. Express, doi:10.7567/APEX.8.075101, Vol. 8, No. 7 (2015) 075101., 2015.07, A new method that enables us to synthesize ultrananocrystalline diamond (UNCD) in powder is proposed. Highly energetic carbon species ejected from a graphite cathode of a coaxial arc plasma gun were provided on a quartz plate at a high density by repeated arc discharge in a compact vacuum chamber, and resultant films automatically peeled from the plate were aggregated and powdered. The grain size was easily controlled from 2.4 to 15.0nm by changing the arc discharge energy. It was experimentally demonstrated that the proposed method is a new and promising method that enables us to synthesize UNCD in powder easily and controllably..
28.	Tomohiro Yoshida, Yūtaro Ueda, Takeshi Daio, Aki Tominaga, Toshihiro Okajima, Tsuyoshi Yoshitake, Heteroepitaxial growth of b-AlN films on sapphire (0001) in nitrogen atmospheres by pulse laser deposition, Jpn. J. Appl. Phys., doi:10.7567/JJAP.54.06FJ05, Vol. 54, No. 6S1, 06FJ05., 2015.06.
29.	Kenji Hanada, Tomohiro Yoshida, You Nakagawa, Hiroki Gima, Aki Tominaga, Masaaki Hirakawa, Yoshiaki Agawa, Takeharu Sugiyama, Tsuyoshi Yoshitake, Hardness and modulus of ultrananocrystalline diamond/hydrogenated amorphous carbon composite films prepared by coaxial arc plasma deposition, Appl. Phys. A, doi: 10.1007/s00339-014-8949-3, Vol. 119, Issue 1, pp 205-210. , 2015.02.
30.	Tomohiro Yoshida, Kenji Hanada, Hiroki Gima, Ryota Ohtani, Kazushi Sumitani, Hiroyuki Setoyama, Aki Tominaga, Tsuyoshi Yoshitake, Influences of repetition rate of arc discharges on hardness and modules of ultrananocrystalline diamond films prepared by coaxial arc plasma deposition, Mater. Res. Express, doi: 10.1088/2053-1591/2/1/015021, Vol. 2, No.1 (2015) 015021., 2015.01.
31.	片宗優貴, 楢木野宏, 花田 賢志, 冨永 亜希, 吉武 剛, 同軸型アークプラズマ堆積法による超ナノ微結晶ダイヤモンド/水素化アモルファスカーボン混相膜の合成, NEW DIAMOND, 第116号, Vol. 31, No. 1, pp. 8-12., 2015.01.
32.	Shinya Ohmagari, Takanori Hanada, Yūki Katamune, Sausan Al-Riyami, Tsuyoshi Yoshitake, Carrier Transport and Photodetection in Heterojunction Photodiodes Comprising n-Type Silicon and p-Type Ultrananocrystalline Diamond/Hydrogenated Amorphous Carbon Composite Films, Jpn. J. Appl. Phys. , 10.7567/JJAP.53.050307, Vol. 53, No. 5, 050307, 2014.05.
33.	Ken-ichiro Sakai, Yuta Noda, takeshi Daio, Daiki Tsumagari, Aki Tominaga, Kaoru Takeda, Tsuyoshi Yoshitake, Current-induced Magnetization Switching at Low Current Densities in CPP Structural Fe3Si/FeSi2 Artificial Lattices, Jpn. J. Appl. Phys. , 10.7567/JJAP.53.02BC15, Vol. 53, Issue 2S, 02BC15, 2014.02.
34.	Ken-ichiro Sakai, Yuta Noda, Daiki Tsumagari, Hiroyuki Deguchi, Kaoru Takeda, Tsuyoshi Yoshitake, Temperature-Dependent Interlayer coupling in Fe3Si/FeSi2 artificial lattices, Phys. Status Solidi A, 10.1002/pssa.201330116, Vol. 211, No. 2, 323-328, 2014.02.
35.	Sausan Al-Riyami, Hiroki Gima, Hiroshi Akamine, Tsuyoshi Yoshitake, Chemical Bonding of Nitrogenated Ultrananocrystalline Diamond Films Deposited on Titanium Substrates by Pulsed Laser Deposition, ECS J. Solid State Sci. Technol., 10.1149/2.016311jss, Vol. 2, issue 11 (2013) M33-38, 2013.11.
36.	Yutaro Ueda, Takeshi Daio, Tomohiro Yoshida, Aki Tominaga, Toshihiro Okajima, Tsuyoshi Yoshitake, Crystalline-Structural Evaluations of Cubic AlN Thin Films Heteroepitaxially Grown on Sapphire(0001) by Pulsed Laser Deposition , Jpn. J. Appl. Phys., 10.7567/JJAP.52.08JE03, Vol. 52, No. 8 (2013) 08JE03., 2013.06, Cubic β-AlN thin films with different thicknesses were grown on sapphire (0001) in nitrogen atmosphere by pulsed laser deposition with sintered AlN targets, and their film structures were evaluated by transmission electron microscopy (TEM) and X-ray diffraction (XRD). It was found that β-AlN layers with a lattice constant of 7.89 Å are epitaxially grown on sapphire (0001) with a relationship of βAlN(111)[111]∥Al2O3(0001)[1100] at film thicknesses of less than 20 nm, and at larger thicknesses, polycrystalline β-AlN grains are grown on the epitaxial β-AlN layers in the Stranski–Krastanov (SK) mode. .
37.	Sausan Al-Riyami, Hiroki Gima, Tsuyoshi Yoshitake, Effects of Hydrogen and Nitrogen Atmospheres on Growth of Ultrananocrystalline Diamond/Amorphous Carbon Composite Films by Reactive Pulsed Laser Deposition, Jpn. J. Appl. Phys., 10.7567/JJAP.52.06GG06, Vol. 52, No. 6 (2013) 06GG06., 2013.06, The growth of ultrananocrystalline diamond/nonhydrogenated amorphous carbon composite films was realized by pulsed laser deposition with a graphite target in a nitrogen atmosphere totally excluding hydrogen. The existence of 7 nm diamond grains was confirmed by X-ray diffraction. Nitrogen incorporation into the films was confirmed by X-ray photoemission and near-edge X-ray absorption structure spectroscopies, and the nitrogenation produced n-type conduction with an electrical conductivity of 0.2 Ω-1· cm-1 at 300 K. The results of study proved that nitrogen acts as a reactive gas for the formation of diamond grains, similarly to hydrogen. .
38.	Yuki Katamune, Shinya Ohmagari, Sausan Al-Riyami, Seishi Takagi, Mahmoud Shaban, Tsuyoshi Yoshitake, Heterojunction Diodes Comprising p-Type Ultrananocrystalline Diamond Films Prepared by Coaxial Arc Plasma Deposition and n-Type Silicon Substrates , Jpn. J. Appl. Phys., 10.7567/JJAP.52.065801, Vol. 52, No. 6 (2013) 065801., 2013.06, Heterojunction diodes, which comprise boron-doped p-type ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/a-C:H) films prepared by coaxial arc plasma deposition and n-type Si substrates, were electrically studied. The current–voltage characteristics showed a typical rectification action. An ideality factor of 3.7 in the forward-current implies that carrier transport is accompanied by some processes such as tunneling in addition to the generation–recombination process. From the capacitance–voltage measurements, the built-in potential was estimated to be approximately 0.6 eV, which is in agreement with that in a band diagram prepared on the assumption that carriers are transported in an a-C:H matrix in UNCD/a-C:H. Photodetection for 254 nm monochromatic light, which is predominantly attributable to photocurrents generated in UNCD grains, was evidently confirmed in heterojunctions. Since dangling bonds are detectable by electron spin resonance spectroscopy, their control might be an important key for improving the rectifying action and photodetection performance. .
39.	Nathaporn Promros, Li Chen, Tsuyoshi Yoshitake, Evaluation of n-Type Nanocrystalline FeSi2/p-Type Si Heterojunctions Prepared by Pulsed Laser Deposition as Near-Infrared Photodetectors, J. Nanosci. Nanotechnol. , 10.1166/jnn.2013.7311, Vol. 13, No. 5 (2013) pp. 3577–3581., 2013.05, n-Type nanocrystalline (NC) FeSi2/p-type Si heterojunctions, which were prepared by pulsed laser deposition, were evaluated as a near infrared photodiode. The built-in potential was estimated to be approximately 1.1 eV from the capacitance–voltage measurement. These junctions showed a rectifying behavior accompanied by a large leakage current. The near infrared light detection performance was evaluated using a 1.33 m laser in the temperature range of 77–300 K. At a reverse bias of −5 V, the detectivity was 55×107 cm Hz1/2 W−1 at 300 K and it was dramatically enhanced to be 80×1010 cm Hz1/2 W−1 at 77 K. It was demonstrated that NC-FeSi2 is a new potential material applicable to NIR photodetectors operating at low temperatures..
40.	Shotra Izumi, Mahmoud Shaban, Nathaporn Promros, Keita Nomoto, Tsuyoshi Yoshitake, Near-Infrared Photodetection of beta-FeSi2/Si Heterojunction Photodiodes at Low Temperatures , Appl. Phys. Lett., http://dx.doi.org/10.1063/1.4789391, Appl. Phys. Lett. Vol. 102, Issue 3 (2013) 032107, 2013.02, n-type b-FeSi2/p-type Si heterojunction photodiodes were fabricated by facing-targets direct-current sputtering, and their near-infrared photodetection properties were studied in the temperature range of 50–300 K. At 300K, devices biased at 5V exhibited a current responsivity of 16.6mA/W. The measured specific detectivity was remarkably improved from 3.5109 to 1.41011 cmHz1/2/W as the devices were cooled from 300K down to 50 K. This improvement is mainly attributable to distinguished suppression in heterojunction leakage current at low temperatures. The obtained results indicate that b-FeSi2/Si heterojunctions offer high potential to be employed as near-infrared photodetectors that are compatible with the current Si technology. V.
41.	E. Garratt, S. AlFaify, Tsuyoshi Yoshitake, Yuki Katamune, M. Bowden, M. Nandasiri, M. Ghantasala, D. C. Mancini, S. Thevuthasan, A. Kayani, Effect of chromium underlayer on the properties of nano-crystalline diamond films, Appl. Phys. Lett., http://dx.doi.org/10.1063/1.4774086, No. 102, Issue 1 (2012) 011913., 2013.01, [URL], This paper investigated the effect of chromium underlayer on the structure, microstructure, and composition of the nano-crystalline diamond films. Nano-crystalline diamond thin films were deposited at high temperature in microwave-induced plasma diluted with nitrogen, on single crystal silicon substrate with a thin film of chromium as an underlayer. Characterization of the film was implemented using non-Rutherford backscattering spectrometry, Raman spectroscopy, near-edge x-ray absorption fine structure, x-ray diffraction, and atomic force microscopy. Nanoindentation studies showed that the films deposited on chromium underlayer have higher hardness values compared to those deposited on silicon without an underlayer. Diamond and graphitic phases of the films evaluated by x-ray and optical spectroscopic analyses determined consistency between the sp2 and sp3 phases of carbon in chromium sample to that of diamond grown on silicon. Diffusion of chromium was observed using ion beam analysis which was correlated with the formation of chromium complexes by x-ray diffraction..
42.	大曲新矢, 花田 賢志, 片宗優貴, 吉田智博, 吉武 剛, 物理気相成長法による超ナノ微結晶ダイヤモンドの生成とドーピングによる結晶粒成長促進効果, 日本結晶成長学会誌, Vol. 39, No. 4 (2012) pp. 193-203, 2012.12.
43.	Nathaporn Promros, Kyohei Yamashita, Ryuhei Iwasaki, Tsuyoshi Yoshitake, Effects of Hydrogen Passivation on Near-Infrared Photodetection of n-Type -FeSi2/p-Type Si Heterojunction Photodiodes, Jpn. J. Appl. Phys. , http://dx.doi.org/10.1143/JJAP.51.108006, Vol. 51, No. 10 (2012) 108006., 2012.10, Hydrogen passivation was applied to the initial epitaxial growth of n-type -FeSi2 thin films on p-type Si(111) substrates. Such passivation was applied at different gas inflow H2/Ar ratios ranging from 0 to 1.0. The photodetection performance of the photodiode fabricated at the optimum ratio of 0.2 was markedly improved as compared with those of the other samples. The quantum efficiency and detectivity were 2.08% and 5:40 109 cmHz1=2W1, respectively. The enhanced photodetective performance should be mainly because dangling bonds that act as trap centers for photocarriers are effectively inactivated by the passivation..
44.	大曲新矢, 吉武 剛, 超ナノ微結晶ダイヤモンド/水素化アモルファスカーボン混相膜の受光素子への応用, 表面科学, http://dx.doi.org/10.1380/jsssj.33.583, Vol. 33, No. 10 (2012) pp. 583-588, 2012.10, [URL], Ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/a-C:H) film is a new candidate material applicable to optoelectronic devices owing to its unique electrical and optical properties. This paper describes a recent progress in the research on the application of semiconducting UNCD/a-C:H films to photodetectors. p-Type conduction accompanied by an enhancement in the carrier concentration was realized by boron doping. Spectral response measurement showed obvious photocurrent in the wavelength of shorter than 280 nm and above 500 nm, which probably originate from UNCD grains and mid-gap states owing to grain boundaries, respectively. Photodiodes comprising p-type UNCD/a-C:H films and n-type Si substrates exhibited a clear response for deep-ultraviolet light, and the external quantum efficiency and responsivity were more than 70% and 130 mA/W, respectively. It was experimentally proved that UNCD/a-C:H is a potential material for the application to photodetectors. .
45.	Nathaporn Promros, Kyohei Yamashita, Shota Izumi, Ryu¯hei Iwasaki, Mahmoud Shaban, Tsuyoshi Yoshitake, Near-Infrared Photodetection of n-Type β-FeSi2/intrinsic Si/p-Type Si Heterojunctions at low temperatures, Jpn. J. Appl. Phys. , http://dx.doi.org/10.1143/JJAP.51.09MF02, Vol. 51, No. 9 (2012) 09MF02., 2012.09.
46.	Shinya Ohmagari, Tsuyoshi Yoshitake, p-Type Ultrananocrystalline Diamond/Hydrogenated Amorphous Carbon Composite Films Prepared by Pulsed Laser Deposition and Their Application to Photodetectors, Jpn. J. Appl. Phys., http://dx.doi.org/10.1143/JJAP.51.090123, Vol. 51, No. 9, (2012) 090123 (Selected Topics in Applied Physics), 2012.07.
47.	Yuki Katamune, Shinya Ohmagari, Tsuyoshi Yoshitake, Boron-Induced Dramatically Enhanced Growth of Diamond Grains in Nanocrystalline Diamond/Hydrogenated Amorphous Carbon Composite Films deposition by Coaxial Arc Plasma Deposition, Jpn. J. Appl. Phys., 10.1143/JJAP.51.078003, Vol. 51, No. 7 (2012) 078003., 2012.07, [URL], Boron-doped nanocrystalline diamond/hydrogenated amorphous carbon composite films were prepared by coaxial arc plasma deposition. The X-ray diffraction measurement exhibited that the diamond grain size is remarkably increased from 2 nm (undoped films) to 82 nm and the lattices of the grains are dilated accompanied by the incorporation of boron atoms into the lattices. The near-edge X-ray absorption fine-structure showed a weak exciton peak of diamond due to the enlarged grains. The enhanced growth mechanism is discussed on the basis of a defect-induced diamond growth model. .
48.	Yuki Katamune, Shinya Ohmagari, Itsuroh Suzuki, Tsuyoshi Yoshitake, Effects of Aluminum Incorporation on Diamond Grain Growth in Ultrananocrystalline Diamond/Hydrogenated Amorphous Carbon Composite Films Prepared by Coaxial Arc Plasma Deposition, Jpn. J. Appl. Phys., 10.1143/JJAP.51.068002, Vol. 51, No. 6 (2012) 068002., 2012.06, [URL], Al-incorporated ultrananocrystalline diamond/hydrogenated amorphous carbon composite films were prepared by coaxial arc plasma deposition with an Al-blended graphite target. The grain size estimated from X-ray diffraction peaks was 27 nm; this value is an order of magnitude larger than that of unincorporated films. The appearance of diamond-200 and 222 peaks, which generally disappear due to the extinction rule of diffraction, and the dilation of lattice, implied the incorporation of Al atoms into the lattices. The near-edge X-ray absorption fine-structure showed a sharp exciton peak due to diamond, which is attributed to the enlarged grains. .
49.	Shinya Ohmagari, Tsuyoshi Yoshitake, Deep-Ultraviolet Light Detection of p-Type Ultrananocrystalline Diamond/Hydrogenated Amorphous Carbon Composite Films, Appl. Phys. Express, 10.1143/APEX.5.065202, Vol. 5, No. 6 (2012) 065202., 2012.06, [URL], Deep-ultraviolet (DUV) light detection of p-type ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/a-C:H) films prepared by pulsed laser deposition was investigated. The photocurrent spectra revealed that the UNCD/a-C:H films possess strong responses in the wavelength range between 210 and 280 nm, which might originate from UNCD grains. The heterojunction photodiodes comprised of p-type UNCD/a-C:H and n-type Si exhibited an obvious photovoltaic action for 254 nm DUV light illumination. The external quantum efficiency and responsivity of the photodiodes were estimated to be 71% and 130 mA/W, respectively. It was proved that UNCD/a-C:H is a new promising material applicable to DUV photodetectors..
50.	Shinya Ohmagari, Yūki Katamune, Hikaru Ichinose, and Tsuyoshi Yoshitake, "Enhanced growth of diamond grains in ultrananocrystalline diamond/hydrogenated amorphous carbon composite films by pulsed laser deposition with boron-blended graphite targets", Jpn. J. Appl. Phys., 10.1143/JJAP.50.035101, Vol. 51, No. 2 (2012) 025503., 2012.02, [URL], Heterojunction diodes comprised of p-type ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/a-C:H) and n-type Si, wherein 3 at. % boron-doped UNCD/a-C:H films were deposited on Si substrates by pulsed laser deposition, were electrically studied. The current–voltage (I–V) characteristics showed the typical rectification action with a leakage current density of 4.7 ×10-5 A/cm2 at a reverse voltage of -1 V. The carrier transport is expected to be in generation–recombination process accompanied by tunneling at low forward voltages of 0.1–0.5 V, and to be predominantly in tunneling at 0.5–1.0 V, from ideality factors estimated from the forward I–V curve. Grain boundaries in the UNCD/a-C:H film might act as centers for tunneling. From the capacitance–voltage measurement, the build-in potential of the heterojunction and an active carrier concentration in the p-type UNCD/a-C:H film were estimated to be 0.6 eV and 1.4 ×1017 cm-3, respectively. .
51.	Ken-ichiro Sakai, Takayuki Sonoda, Shin-ichi Hirakawa, Kaoru Takeda, and Tsuyoshi Yoshitake, Current-Induced Magnetization Switching in Fe3Si/FeSi2 Artificial Lattices, Jpn. J. Appl. Phys., 10.1143/JJAP.50.08JD06, Vol. 51, No. 2 (2012) 028004., 2012.02, [URL], Fe3Si/FeSi2/Fe3Si trilayered films were grown on Si(111) substrates at a substrate temperature of 300 °C by facing-targets direct-current sputtering, and current-induced magnetization switching in current-perpendicular-to-plane geometry was studied for the films wherein an antiferromagnetic interlayer coupling perpendicular to the plane was probably formed at room temperature. The appearance of a hysteresis loop in the electrical resistance–injection current curve well coincided with that of a hysteresis loop in the magnetization curve perpendicular to the plane. In addition, the hysteresis loop in the electrical resistance–injection current curve disappeared under large magnetic fields. The origin of the change in the electrical resistance for the injection current might be the change in the interlayer coupling. .
52.	Nathaporn Promros, Kyohei Yamashita, Chen Li, Kenji Kawai, Mahmoud Shaban, Toshihiro Okajima, and Tsuyoshi Yoshitake, n-Type Nanocrystalline FeSi2/intrinsic Si/p-Type Si Heterojunction Photodiodes fabricated by Facing-Targets Direct-Current Sputtering, Jpn. J. Appl. Phys., 10.1143/JJAP.51.021301, Vol. 51, No. 2 (2012) 021301., 2012.01, [URL], n-Type nanocrystalline (NC) FeSi2/intrinsic (i) Si/p-type Si heterojunctions, which were prepared by facing-target direct current sputtering, were evaluated as near-infrared photodiodes, and the effects of thin i-Si layer insertion on diode performance were studied. Their junction capacitance and reverse leakage current were clearly reduced compared with those of n-type NC-FeSi2/p-type Si heterojunctions. The capacitance–voltage curve implied that the effects of interface states is relatively suppressed by i-Si insertion. The near-infrared light detection performance was investigated using a 1.33 µm laser in the temperature range of 77–300 K. The detectivities at 300 and 77 K were 1.9 ×108 and 3.0 ×1011 cm Hz1/2 W-1, respectively, at a negative bias of -5 V, which were markedly improved compared with that of p–n heterojunctions. This might be because the formation of interface states that act as trap centers for photocarriers is suppressed. .
53.	Shin-ichi Hirakawa, Takayuki Sonoda, Ken-ichiro Sakai, Kaoru Takeda1, and Tsuyoshi Yoshitake, Temperature-Dependent Current-Induced Magnetization Switching in Fe3Si/FeSi2/Fe3Si trilayered films, Jpn. J. Appl. Phys., 10.1143/JJAP.50.08JD06, Vol. 50, No. 8 (2011) 08JD06., 2011.08, [URL], Fe3Si/FeSi2/Fe3Si trilayered films were grown on Si(111) substrates at a substrate temperature of 300 °C by facing-targets direct-current sputtering, and current-induced magnetization switching in current-perpendicular-to-plane geometry was studied for the films wherein an antiferromagnetic interlayer coupling perpendicular to the plane was probably formed at room temperature. The appearance of a hysteresis loop in the electrical resistance–injection current curve well coincided with that of a hysteresis loop in the magnetization curve perpendicular to the plane. In addition, the hysteresis loop in the electrical resistance–injection current curve disappeared under large magnetic fields. The origin of the change in the electrical resistance for the injection current might be the change in the interlayer coupling. .
54.	Sausan Al-Riyami, Shinya Ohmagari, and Tsuyoshi Yoshitake, Near-Edge X-ray Absorption Fine-Structure Spectroscopic Study on Nitrogen-Doped Ultrananocrystalline Diamond/Hydrogenated Amorphous Carbon Composite Films Prepared by Pulsed Laser Deposition, Jpn. J. Appl. Phys., 10.1143/JJAP.50.08JD05, Vol. 50, No. 8 (2011) 08JD05., 2011.08, [URL], Nitrogen-doped ultrananocrystalline diamond (UNCD)/hydrogenated amorphous carbon (a-C:H) composite films, which possessed n-type conduction with enhanced electrical conductivity, were prepared by pulsed laser deposition. The film doped with a nitrogen content of 7.9 at. % possessed enhanced electrical conductivity of 18 Ω-1·cm-1 at 300 K. The near-edge X-ray absorption fine-structure (NEXAFS) measurement indicated the appearance of additional peaks due to π* C=N, σ* C=N, and σ* C–N bonds compared with the spectra of undoped films. The sp2 bonding fraction estimated from the NEXAFS spectra increased with the nitrogen content. The enhanced electrical conductivity is probably due to the formation of additional π* and σ* states and the enhancement in the sp2 bonding fraction. .
55.	大曲新矢，吉武剛, 超ナノ微結晶ダイヤモンド/水素化アモルファスカーボンを用いたフォトダイオードの作製, NEW DIAMOND, 第102号, Vol. 27, No. 3 (2011) pp. 40-41., 2011.07.
56.	Al-Riyami Sausan, Shinya Ohmagari, and Tsuyoshi Yoshitake, Fourier Transform Infrared Spectroscopic Study of Nitrogen-Doped Ultrananocrystalline Diamond/Hydrogenated Amorphous Carbon Composite Films Prepared by Pulsed laser Deposition, Diamond Relat. Mater., Vol. 20 (2011) pp. 1072-1075., 2011.06.
57.	Shinya Ohmagari, Sausan Al-Riyami, and Tsuyoshi Yoshitake, p-Type ultrananocrystalline diamond/hydrogenated amorphous carbon composite/n-type Si heterojunction diodes fabricated by pulsed laser deposition, Jpn. J. Appl. Phys. , 10.1143/JJAP.49.031302, Vol. 50, No. 3, 035101., 2011.03, [URL], p-Type ultrananocrystalline diamond (UNCD)/hydrogenated amorphous carbon (a-C:H) composite films were fabricated by pulsed laser deposition using boron-doped graphite targets. Thermal analysis confirmed the occurrence of p-type conduction. The electrical conductivity increased with the doped amount of boron. An activation energy estimated from the Arrhenius plot was approximately 0.1 eV. Near-edge X-ray absorption fine structure spectra revealed that the σ*C–H peak weakened and the σ*C–B peak strengthened with an increase in the doped amount of boron. Fourier transform infrared spectroscopy showed that the sp3 C–H peak weakened with the doped amount of boron. These probably indicate that the hydrogen atoms that terminate the dangling bonds of UNCD crystallites are partially replaced with boron atoms. .
58.	吉武 剛，大曲新矢，アリヤミ サウサン，大谷亮太，隅谷和嗣，瀬戸山寛之，小林英一，岡島敏浩，平井康晴, 超ナノ微結晶ダイヤモンド/水素化アモルファスカーボンの受光素子への応用に向けた基盤研究, NanotechJapan Bulletin, Vol. 4, No. 1 (2011) フォーカス26., 2011.02, [URL].
59.	Kenji Hanada, Tomohiro Yoshida, You Nakagawa, and Tsuyoshi Yoshitake, Formation of Ultrananocrystalline Diamond/Amorphous Carbon Composite Films in Vacuum by Using A Coaxial Arc Plasma Gun, Jpn. J. Appl. Phys., 10.1143/JJAP.49.125503, Vol. 49, No. 12 (2010) 125503., 2010.12, [URL], Ultrananocrystalline diamond (UNCD)/nonhydrogenated amorphous carbon (a-C) composite films were grown in vacuum using a coaxial arc plasma gun. From the X-ray diffraction measurement, the UNCD crystallite size was estimated to be 1.6 nm. This size is dramatically reduced from that (2.3 nm) of UNCD/hydrogenated amorphous carbon (a-C:H) composite films grown in a hydrogen atmosphere. The sp3/(sp3 + sp2) value, which was estimated from the X-ray photoemission spectrum, was also reduced to be 41%. A reason for it might be the reduction in the UNCD crystallite size. From the near-edge X-ray absorption fine-structure (NEXAFS) spectrum, it was found that the π*C=C and π*C≡C bonds are preferentially formed instead of the σ*C–H bonds in the UNCD/a-C:H films. Since the extremely small UNCD crystallites (1.6 nm) correspond to the nuclei of diamond, we consider that UNCD crystallite formation should be due predominantly to nucleation. The supersaturated condition required for nucleation is expected to be realized in the deposition using the coaxial arc plasma gun. .
60.	Mahmoud Shaban, Kenji Kawai, Nathaporn Promros, and Tsuyoshi Yoshitake, n-Type Nanocrystalline-FeSi2/p-Type Si Heterojunction Photodiodes Prepared at Room Temperature, IEEE Electron Device Lett., Vol. 31, No. 12, pp. 1428-1430., 2010.12.
61.	Sausan Al-Riyami, Shinya Ohmagari, and Tsuyoshi Yoshitake, Electrical Properties and Chemical Bonding Structures of Nitrogen-doped Ultrananocrystalline Diamond/Hydrogenated Amorphous Carbon Composite Films Prepared by Pulsed Laser Deposition, Appl. Phys. Express, 10.1143/APEX.3.115102, Vol. 3, No. 11 (2010) 115102., 2010.11, [URL], Nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/a-C:H) films were deposited by pulsed laser deposition. The film doped with a nitrogen content of 7.9 at.% possessed n-type conduction with an electrical conductivity of 181cm1 at 300 K. A heterojunction with p-type Si exhibited typical rectifying action. The UNCD grain size was estimated to be 2.5nm from X-ray diffraction measurement. Near-edge X-ray absorption fine-structure and Fourier transform infrared spectroscopies revealed the preferential formations of C¼N and C–N bonds and an enhanced amount of sp2 bonds in the films..
62.	Kenji Hanada, Tsuyoshi Yoshitake, Takashi Nishiyama, and Kunihito Nagayama, Time-Resolved Spectroscopic Observation of Deposition Processes of Ultrananocrystalline Diamond/Amorphous Carbon Composite Films by Using a Coaxial Arc Plasma Gun, Jpn. J. Appl. Phys., 10.1143/JJAP.49.08JF09, Vol. 49, No. 8 (2010) 08JF09., 2010.08, [URL].
63.	吉武 剛, 超ナノ微結晶ダイヤモンド/水素化アモルファスカーボン混相膜の化学結合構造と機械物性, まてりあ, 第49巻 第7号 (2010) pp. 317-319., 2010.07.
64.	Kenji Hanada, Takashi Nishiyama, Tsuyoshi Yoshitake, and Kunihito Nagayama, Optical Emission Spectroscopic of Deposition Process of Ultrananocrystalline Diamond/Hydrogenated Amorphous Carbon Composite Films by Using a Coaxial Arc Plasma Gun, Diamond Relat. Mater., in press, 2010.05.
65.	Kazushi Sumitani, Ryota Ohtani, Tomohiro Yoshida, You Nakagawa, Satoshi Mohri, Tsuyoshi Yoshitake, Influences of repetition rate of laser pulses on growth of crystalline AlN films on sapphire(0001) substrates by pulsed laser deposition, Diamond Relat. Mater., Vol. 19 (2010) pp. 618-620., 2010.04.
66.	Sausan Al-Riyami, Shinya Ohmagari, and Tsuyoshi Yoshitake, X-ray Photoemission Spectroscopy of Nitrogen-Doped UNCD /a-C:H Films Prepared by Pulse Laser Deposition, Diamond Relat. Mater., 10.1016/j.diamond.2010.01.023, Vol. 19 (2010) pp. 510-513., 2010.04.
67.	Shinya Ohmagari, Tsuyoshi Yoshitake, Akira Nagano, Ryota Ohtani, Hiroyuki Setoyama, Eiichi Kobayashi, and Kunihito Nagayama, X-ray photoemission spectroscopy study of ultrananocrystalline diamond/hydrogenated amorphous carbon films prepared by pulsed laser deposition, Diamond Relat. Mater., in press, 2010.04.
68.	Shinya Ohmagari, Tsuyoshi Yoshitake , Akira Nagano, Ryota Ohtani, Hiroyuki Setoyama, Eiichi Kobayashi, Takeshi Hara, and Kunihito Nagayama, Formation of p-Type Semiconducting Ultrananocrystalline Diamond/Hydrogenated Amorphous Carbon Composite Films by Boron Doping, Jpn. J. Appl. Phys., 10.1143/JJAP.49.031302, Vol. 49, No. 3 (2010) 031302, 2010.03, [URL].
69.	Kazushi Sumitani , Ryota Ohtani, Tomohiro Yoshida, You Nakagawa, Satoshi Mohri, and Tsuyoshi Yoshitake, Synchrotron X-ray Diffraction Study of Single-Phase β-AlN Thin Film Heteroepitaxially Grown on a Sapphire(0001) Substrate by Pulsed Laser Deposition, Jpn. J. Appl. Phys. , Vol. 49, No. 2 (2010) 020212., 2010.02.
70.	Tsuyoshi Yoshitake, You Nakagawa, Akira Nagano, Ryota Ohtani, Hiroyuki Setoyama, Eiichi Kobayashi, Kazushi Sumitani, Yoshiaki Agawa, and Kunihito Nagayama, Structural and physical characteristics of ultrananocrystalline diamond/hydrogenated amorphous carbon composite films deposited using a coaxial arc-plasma gun, Jpn. J. Appl. Phys., 10.1143/JJAP.49.015503, Vol. 49, No. 1, 015503, 2010.01, [URL].
71.	Mahmoud Shaban, Shota Izumi, Keita Nomoto, and Tsuyoshi Yoshitake, "n-Type β-FeSi2/intrinsic-Si/p-type Si heterojunction photodiodes for near-infrared light detection at room temperature", Appl. Phys. Lett., 10.1063/1.3250171 , Vol.95 (2009) 162102., 2009.10, [URL].
72.	Mahmoud Shaban, Keita Nomoto, Shota Izumi, and Tsuyoshi Yoshitake, "Characterization of near-infrared n-type β-FeSi2/p-type Si heterojunction photodiodes at room temperature", Appl. Phys. Lett., 10.1063/1.3151915 , 94 (2009) 222113., 2009.06, [URL].
73.	Shinya Ohmagari, Tsuyoshi Yoshitake, Akira Nagano, Sausan AL-Riyama, Ryota Ohtani, Hiroyuki Setoyama, Eiichi Kobayashi and Kunihito Nagayama, "Near-edge X-ray absorption fine-structure of ultrananocrystalline diamond/amorphous carbon films prepared by pulsed laser deposition", J. Nanomater., in press, 2009.03.
74.	Tsuyoshi YOSHITAKE , Akira NAGANO, Shinya OHMAGARI, Masaru ITAKURA, Noriyuki KUWANO, Ryota OHTANI, Hiroyuki SETOYAMA, Eiichi KOBAYASHI, and Kunihito NAGAYAMA, "Near-edge X-ray absorption fine-structure, X-ray photoemission, Fourier transfer infrared spectroscopies of ultrananocrystalline diamond/hydrogenated amorphous carbon composite films" , Jpn. J. Appl. Phys., 10.1143/JJAP.48.020222, Vol. 48, No. 2 (2009) 020222., 2009.02, [URL].
75.	Kenji Hanada, Takashi Nishiyama, Tsuyoshi Yoshitake, and Kunihito Nagayama, "Time-resolved Observation of Deposition Process of Ultrananocrystalline Diamond/Hydrogenated Amorphous Carbon Composite Films in Pulsed Laser Deposition", J. Nanomater., 2009 (2009) 901241., 2009.01.
76.	Akira NAGANO and Tsuyoshi YOSHITAKE, Takeshi HARA and Kunihito NAGAYAMA, "Optical properties of ultrananocrystalline diamond/amorphous carbon composite films prepared by pulsed laser deposition", Diamond Rel. Mater., 17, pp. 1199-1202., 2008.08.
77.	Satoshi MOHRI, Tsuyoshi YOSHITAKE, Takeshi HARA, and Kunihito NAGAYAMA, "Growth of metastable cubic AlN by reactive pulsed laser deposition", Diamond Rel. Mater., 17, pp. 1796-1799, 2008.08.
78.	Mahmoud SHABAN, Haruhiko KONDO, Kazuhiro NAKASHIMA, and Tsuyoshi YOSHITAKE, "Electrical and Photovoltaic Properties of n-Type Nanocrystalline FeSi2/p-Type Si Heterojunctions Prepared by Facing Target Direct-current Sputtering at Room Temperature", Jpn. J. Appl. Phys, 10.1143/JJAP.47.5420, Vol. 47, No. 7, pp. 5420-5422., 2008.07, [URL].
79.	Mahmoud SHABAN, Keita NOMOTO, Kazuhiro NAKASHIMA, and Tsuyoshi YOSHITAKE, "Low-temperature Annealing of n-type β-FeSi2/p-type Si Heterojunctions" , Jpn. J. Appl. Phys, Vol. 47, No. 5, pp. 3444-3446., 2008.05.
80.	Tsuyoshi YOSHITAKE , Satoshi MOHRI, Takeshi HARA, and Kunihito NAGAYAMA, "Growth of metastable β-AlN by pulsed laser deposition", Jpn. J. Appl. Phys, Vol. 47, No. 5, pp. 3600-3602, 2008.05.
81.	Kaoru TAKEDA, Tsuyoshi YOSHITAKE , Yoshiki SAKAMOTO, Tetsuya OGAWA, Daisuke HARA, Masaru ITAKURA, Noriyuki KUWANO, Toshinori KAJIWARA, and Kunihito NAGAYAMA, "Enhanced interlayer coupling and magnetoresistance ratio in Fe3Si/FeSi2 superlattices", Appl. Phys. Express, Vol. 1, No. 2 (2008) 021302., 2008.02.
82.	Mahmoud SHABAN, Kazuhiro NAKASHIMA, and Tsuyoshi YOSHITAKE, "Substrate Temperature Dependence of Photovoltaic Properties of β-FeSi2/Si Heterojunctions Prepared by Facing-target DC Sputtering" , Jpn. J. Appl. Phys. Part 1, Vol. 46, No. 12, pp. 77087710, 2007.12.
83.	Kaoru TAKEDA, Tsuyoshi YOSHITAKE, Dai NAKAGAUCHI, Tetsuya OGAWA, Daisuke HARA, Masaru ITAKURA, Noriyuki KUWANO, Yoshitsugu TOMOKIYO, Toshiyuki KAJIWARA, and Kunihito Nagayama, "Epitaxy in Fe3Si/FeSi2 superlattices prepared by facing target direct-current sputtering at room tempertaure", Jpn. J. Appl. Phys. Part 1, Vol. 46, No. 12, pp. 78467848., 2007.12.
84.	Tsuyoshi YOSHITAKE, Akira NAGANO, Masaru ITAKURA, Noriyuki KUWANO, Takeshi HARA, and Kunihito NAGAYAMA, "Spectral absorption properties of ultrananocrystalline diamond/amorphous carbon composite thin films prepared by pulsed laser deposition", Jpn. J. Appl. Phys. Part 2, 10.1143/JJAP.46.L936, Vol.46, No.38, pp.L936 - L938, 2007.10, [URL].
85.	Mahmoud SHABAN, Kazuhiro NAKASHIMA, Wataru YOKOYAMA, and Tsuyoshi YOSHITAKE, "Photovoltaic Properties of n-type β-FeSi2/p-type Si Heterojunctions", Jpn. J. Appl. Phys. Part2, 10.1143/JJAP.46.L667, Vol.　46,　No.27,　pp.　L667-L669, 2007.07, [URL].
86.	T. Yoshitake, T. Ogawa, D. Nakagauchi, D. Hara, M. Itakura, N. Kuwano, Y. Tomokiyo, K. Takeda, T. Kajiwara, M. Ohashi, G. Oomi and K. Nagayama, "Interlayer coupling in ferromagnetic epitaxial Fe3Si/FeSi2 superlattices", Appl. Phys. Lett., 10.1063/1.2410222 , 89, 253110, 2006.12, [URL].
87.	T. Yoshitake, Y. Inokuchi, A. Yuri, and K. Nagayama, "Direct epitaxial growth of semiconducting beta-FeSi2 thin films by facing targets direct-current sputtering", Appl. Phys. Lett., 10.1063/1.2200153 , 88, 182104, 2006.06, [URL].
88.	K. Takarabe, H. Doi, Y. Mori, K. Fukui, T. Yoshitake, K. Nagayama, "Enhanced optical absorption in nano crystalline FeSi2 and hydrogenation effect on its characteristic energy", Appl. Phys. Lett., 88, 061911, 2006.02.
89.	T. Yoshitake, D. Nakagauchi, T. Ogawa, M. Itakura, N. Kuwano, Y. Tomokiyo, T. Kajiwara, and K. Nagayama, "Room-temperature epitaxial growth of ferromagnetic Fe3Si films on Si(111) by facing target direct-current sputtering", Appl. Phys. Lett., 10.1063/1.1978984, 86, 26, 86, 262505, 2005.09.
90.	Tsuyoshi Yoshitake, Takeshi Hara, Tomohito Fukugawa, Ling yun Zhu, Masaru Itakura, Noriyuki Kuwano, Yoshitsugu Tomokiyo and Kunihito Nagayama, "Low-Temperature Growth of Nanocrystalline Diamond by Reactive Pulsed Laser Deposition under a Hydrogen Atmosphere", Jpn. J. Appl. Phys. Part2, 10.1143/JJAP.43.L240, 43, 2B, L240-L242, Vol. 43, pp. L 240–L 242, 2004.06.
91.	T. Yoshitake, M. Yatabe, M. Itakura, N. Kuwano, Y. Tomokiyo, and K. Nagayama, "Semiconducting nanocrystalline iron disilicide thin films prepared by pulsed-laser ablation", Appl. Phys. Lett., 10.1063/1.1617374, 83, 15, 3057-3059, Vol. 83,　3057-3059., 2003.10.
92.	Tsuyoshi Yoshitake, Takashi Nishiyama and Kunihito Nagayama, "Homo-Growth of Diamond Single Phase Thin Films by Pulsed Laser Ablation of Graphite", Jpn. J. Appl. Phys. Part2, Vol.40,　No.6A pp.L573 - L575., 2001.06.
93.	Tsuyoshi Yoshitake, Gousuke Shiraishi, and Kunihito Nagayama, "Droplet-free thin films deposited by pulsed laser deposition using a mechanical filter", Jpn. J. Appl. Phys. Part1, Vol. 41,　836-837, 2001.02.

主要総説, 論評, 解説, 書評, 報告書等

主要学会発表等

1.	Tsuyoshi Yoshitake, Nanodiamond film formation by physical vapor deposition and their applications, Campus Asia EEST Asia 2020 Summer School, 2020.08.
2.	Tsuyoshi Yoshitake, Mohamed Egiza, Kouki Murasawa, Ali M. Ali, Yasuo Fukui, Hidenobu Gonda, and Masatoshi Sakurai, Boron Doping Effects on Mechanical Properties of Ultrananocrystalline Diamond/Amorphous Carbon Composite Films Deposited on Cemented Carbide Substrates by Coaxial Arc Plasma Deposition, 2019年第80回応用物理学会秋季学術講演会, 2019.09.
3.	吉武 剛、エギザ モハメド、村澤 功基、アリ アリ モハメド、福井 康夫、権田 英修、櫻井 正俊, 同軸型アークプラズマ堆積法により超硬合金上に堆積される超ナノ微結晶ダイヤモンド膜の機械特性への成膜時のバイアス印加効果, 2018年第79回応用物理学会秋季学術講演会, 2018.09.
4.	吉武 剛，アブバクル エスラム，ゼクリア アブデルラーマン，片宗 優貴，大曲 新矢，池上 浩, ドーパントを含む溶液中におけるレーザー照射ドーピングのダイヤモンドへの適用, 2018年第79回応用物理学会秋季学術講演会, 2018.09.
5.	Tsuyoshi Yoshitake, Eslam Abubakr, Hiroshi Ikenoue, Application of laser-induced doping in liquids containing dopants to diamond, OIST Diamond Workshop, 2017.10.
6.	Tsuyoshi Yoshitake, Widely-variable electrical conductivity of ultrananocrystalline diamond/hydrogenated amorphous carbon composite films prepared by PVD, 3rd French-Japanese Workshop on Diamond Power Devices, 2015.07.
7.	Tsuyoshi Yoshitake, Preparation of Ultrananocrystalline Diamond/Hydrogenated Amorphous Carbon Composite Films Prepared by Physical Vapor Deposition and Their Application to Photodiodes and Hard Coating, Hasselt Diamond Workshop 2015 SBDD XX, 2015.02.
8.	Tsuyoshi Yoshitake, Yuki Katamune, Takanori Hanada, Satoshi takeichi, Shinya Ohmagari, Application of Ultrananocrystalline Diamond/Hydrogenated Amorphous Carbon Composite Films to Photodiodes, Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2014), 2014.12.
9.	Tsuyoshi Yoshitake, Yuki Katamune, Takanori Hanada, Hiroki Gima, Abdelrahman M. Ahmed, Shinya Ohmagari, Sausan Al-Riyami, Kenji Hanada, Growth of UNCD/a-C:H composite films by PVD and their electrical conductivity control, Japan-France Workshop on Diamond Power Devices, 2014.10.
10.	Tsuyoshi Yoshitake, Present state of research on photodiodes comprising iron disilicides and problems awaiting solution, International conference and summer school on advanced silicide technology 2014, 2014.07, Semiconducting iron disilicide is a new candidate applicable to near-infrared-wavelength photoelec-tronic devices [1-3], because it possesses features such as a direct optical band gap of 0.85 eV above an indirect gap (0.76 eV) and a large absorption coefficient, which is 10^5 cm1 at 1.0 eV[4]. Since beta-FeSi2 can be epitaxially grown on Si due to small lattice mismatches, a heterojunction diode comprising a beta-FeSi2 thin film and singlecrystalline Si substrate is a device that can be briefly formed by employing vapor deposition. For near-infrared light detection in the Si/beta-FeSi2 heterojunction diodes, near-infrared light transmitted through the front-side Si substrate can be absorbed in the depletion region of the back-side beta-FeSi2 thin film. In our previous works, we have progresses researches on p-type Si/n-type beta-FeSi2 heterojunction diodes, totally from the epitaxially growth of beta-FeSi2 thin film on Si(111) by sputtering [5] to the evaluation of p-type Si/n-type beta-FeSi2 heterojunctions as photodetectors [6,7]. It was confirmed that beta-FeSi2 in the heterojunction evidently con-tributes to the photodetection of near-infrared light from the photoresponse spectrum of the heterojunction, as shown in Fig. 1. In addition, as shown in Fig.2, the heterojunction clearly exhibited current due to photogenerated carriers for 1.33 micrometer monochromatic light in the I-V curves in comparison with that in the dark. The detectivity at temperatures lower than 100 K reach approximately 2*10^11 cmHz^1/2 /W, which is comparable with that of existing near infrared photodiodes comprising PbS and InAs at the same temperature. However, the external quantum efficiency is less than 10 % [6,7]. In this presentation, the progress thus far of our research and recent problems that we are facing and should be solved for the next step will be introduced. A serious problem for p-type Si/n-type beta-FeSi2 heterojunctions is that a barrier due to a band offset appears in the valence band and it prevents from the flow of photogenerated carriers from the n-type beta-FeSi2 layer to the p-type Si layer. The opposite combination, namely n-type Si/p-type beta-FeSi2, is structurally ideal because of it has no barriers due to the band offset. In order to form p-type -FeSi2, the residual carrier density should be reduced for controlling the conduction type. Carbon doping, which might be effective for a reduction in the carrier density, will be introduced. [1] D. Leong, M. Harry, K. J. Reeson, and K. P. Homewood, Nature (London) 387 (1997) 686. [2] Y. Maeda, T. Akita, K. Umezawa, K. Miyake, M. Sagawa, SPIE Proc. 3419 (1998) 341916. [3] T. Ootsuka, Y. Fudamoto, M. Osamura, T. Suemasu, Y. Makita, Y. Fukuzawa, and Y. Nakayama, Appl. Phys. Lett. 91 (2007) 142114. [4] H. Udono, I. Kikuma, T. Okuno, Y. Matsumoto, and H. Tajima: Appl. Phys. Lett. 85 (2004) 1937. [5] .M. Shaban, S. Izumi, K. Nomoto, and T. Yoshitake, Appl. Phys. Lett. 95 (2009) 162102. [6] N. Promros, K. Yamashita, S. Izumi, R. Iwasaki, M. Shaban, and T. Yoshitake, Jpn. J. Appl. Phys. 51 (2012) 09MF02. [7] S. Izumi, M. Shaban, N. Promros, K. Nomoto, and T. Yoshitake, Appl. Phys. Lett. 102 (2013) 032107..
11.	Tsuyoshi Yoshitake, Ecologically Friendly Semiconductors: Iron Disilicides and Ultrananocrystalline Diamond/Hydrogenated Amorphous Carbon, IUMRS-International Conference on Electronic Materials (IUMRS-ICEM 2012), 2012.09.

特許出願・取得

所属学会名

学協会役員等への就任

学会大会・会議・シンポジウム等における役割

学術論文等の審査

海外渡航状況, 海外での教育研究歴

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