奥野 剛史

基盤理工学専攻教授
Ⅲ類(理工系)教授
社会連携センター教授
  • プロフィール:

    新規ナノ光材料や半導体微細構造における光物性実験を専門としています。 量子ドットやナノワイヤ等の量子閉じ込め構造の光学的性質、および、 それらと発光中心との相互作用を明らかにするための研究を行っています。 大きさがナノメートル(10-9 m)領域になった半導体微細構造では、 その中の電子のもつ波としての性質が顕著になってきます。 そのため、発光する色や応答速度等が、通常の大きさの半導体とは変わってきて、 自由に制御できる可能性がでてきます。また、そこに蛍光イオンを導入することにより、 通常とは異なる強度や色で発光させることができます。 このような新規ナノ光材料を創出し、その構造や発光メカニズムを解明しようとしています。


    低消費エネルギーに資しかつ環境に調和した新物質および新現象を探索しています。 これまでの研究において得た結果の例を記します。 LED電球でエネルギー蓄積可能な赤色の硫化物残光蛍光体を得ました。残光(蓄光)蛍光体は、安全標識や時計の文字盤等に緑色のものが実用化されています。しかしその性能は発展途上で、暗がりで電気スイッチの位置を示す残光シールが翌朝まで十分な明るさで光り続けることはありません。そして現状の残光蛍光体は、紫外光でエネルギーを蓄積します。現在普及がすすんでいるLED電球は紫外光成分を含まないため、残光の強度は小さく時間は短くなってしまいます。そこで、赤色に発光するイオンとエネルギー蓄積に寄与するイオンを選び、ヨウ素蒸気を援用するという独自の蛍光体作製手法により、実用化にいたっていない赤色残光を得ることに成功しました。微弱光を注意深く検出する実験により、可視光によって、赤色残光をもたらすエネルギー蓄積が生じることを明瞭に示しました。残光の強度と時間をさらに伸長するための研究を継続しています。昼間の太陽光をうけて夜中じゅう翌朝まで光り続ける残光シールが実現したとすると、街灯のない道路のガードレールにはれば昼間の太陽エネルギーを夜間に光として使用できることになります。省エネルギーおよび安全安心な社会のためにおおいに資することになります。  


    シリコンを構成元素に含む新しい黄色蛍光体を見い出しました。 蛍光体の母体材料としてGd4(SiS4)3およびY4(SiS4)3を 発光ダイオードなどの青色光で励起すると、 3価のセリウムイオンが黄色で発光します。効率は最高で62%に達します。 これまでの蛍光体では、セリウムイオン自身を青色光で励起する ことが多いのですが、この蛍光体では 母体を励起してもセリウムイオンまでほぼ100%の効率でエネルギーが 伝達されることがわかりました。 様々なイオンを用いて様々な発光色を得る、 母体の材料を制御して変更することにより様々な励起光源が 使用可能になる、などの利点が考えられます。  


    Ca2SiS4:Eu2+などの新しいチオシリケート蛍光体材料は、粉末体の作製報告がいくつかなされていました。それらをシリコン基板上に作製することに成功しています。LSIを用いた光源などに 応用できる可能性があります。バリウムやカルシウム、ユーロピウムといった 材料を適切に選んでやることにより、緑色、黄色、および赤色に対応する発光スペクトルを 得ました。

学位

  • 博士(理学), 東京大学

研究キーワード

  • 蛍光体科学
  • 光物性実験

研究分野

  • ナノテク・材料, 無機材料、物性
  • ナノテク・材料, 応用物性

経歴

  • 2004年04月 - 2015年03月
    電気通信大学 電気通信学部, 助教授、准教授
  • 2001年08月 - 2004年03月
    筑波大学 物理学系, 講師
  • 1995年04月 - 2001年07月
    筑波大学 物理学系, 助手

学歴

  • 1995年03月
    東京大学, 理学系研究科, 物理学専攻
  • 1990年03月
    東京大学, 理学部, 物理学科

委員歴

  • 2012年04月 - 現在
    評議員, 日本物理教育学会, 学協会
  • 2019年04月 - 2021年03月
    光源・照明システム分科会幹事, 照明学会, 学協会
  • 2017年04月 - 2021年03月
    大学の物理教育編集委員会委員, 日本物理学会, 学協会
  • 2017年04月 - 2019年03月
    固体光源分科会幹事, 照明学会, 学協会
  • 2013年04月 - 2017年03月
    物理教育委員, 日本物理学会, 学協会
  • 2012年04月 - 2014年03月
    プログラム編集委員(中分類14.4半導体B 光物性・発光デバイス), 応用物理学会, 学協会
  • 2005年09月 - 2008年08月
    会誌編集委員, 日本物理学会, 学協会

論文

  • The decay curves of luminescence from Eu2+ in β-SiAlON are effectively analyzed using the general-order kinetics formula
    Yoriko Suda; Tsuyoshi Okuno; Takashi Takeda; Kohsei Takahashi; Naoto Hirosaki
    Journal of Physics D: Applied Physics, IOP Publishing, 57巻, 18号, 掲載ページ 185101-1-185101-11, 出版日 2024年02月07日, 査読付, Abstract

    Defects in phosphors affect not only luminescence intensity but also emission peak width, decay time, and afterglow. The green phosphor β-SiAlON:Eu2+ exhibits the green emission of Eu2+ at 520 nm and the blue emission of nitrogen vacancies at 460 nm in time-resolved fluorescence measurements. The decay time of the intrinsic Eu2+ transition is 0.7 μs, but afterglow is detected from 50 μs to 0.01 s. This afterglow decay curve is the same for the green emission of Eu2+ and the blue emission of nitrogen vacancies, suggesting that the defect levels of the nitrogen vacancies affect the Eu2+ transition. The afterglow decay curves were analyzed using the formula of the general-order kinetics, ${\left( {1 + t/{\tau _{\text{B } } } } \right)^{ - n } }$, where $n$ is the decay power and ${\tau _{\text{B } } }$ is the decay time. This equation is generally used when analyzing afterglow on the order of seconds to hours but has not been examined systematically applied in samples with different concentrations of Eu2+ and temperatures on the order of nanoseconds to milliseconds. The decay power $n$ is approximately 1 for all Eu2+ concentrations (x = 0.001–0.3) and undoped β-SiAlON. The decay time ${\tau _{\text{B } } }$ is correlated with the density of the nitrogen vacancies determined by electron spin resonance. Furthermore, the value of $n$ is approximately 1 for 50 μs to 0.01 s and 0.3 for 1–1000 s. Thus, the luminescence mechanism of Eu2+ can be discussed by comparing $n$ and ${\tau _{\text{B } } }$ obtained from the decay curves. In addition, several different Eu2+-doped phosphors, namely SrAl2O4:Eu2+, Dy3+, CaAlSiN3:Eu2+, and CaS:Eu2+, Tm3+, are studied.
    研究論文(学術雑誌), 英語
  • Red photostimulated luminescence and afterglow in CaS:Eu2+, Mn2+ phosphors
    Kazuaki Iguchi; Yuta Nishigawa; Yoriko Suda; Yasushi Nanai; Tsuyoshi Okuno
    責任著者, Journal of Physics D: Applied Physics, IOP Publishing, 57巻, 7号, 掲載ページ 075301-1-075301-11, 出版日 2023年11月16日, 査読付, Abstract

    In afterglow phosphors, luminescence appears and can be observed with the naked eye for minutes to hours or more, even after photoexcitation ceases. Red afterglow and photostimulated luminescence (PSL) at 650 nm are studied in CaS:Eu2+, Mn2+ phosphors. Infrared light at 980 nm from a laser diode induces the red PSL for 990 s. Two types of trap states are found to be present in the phosphors by using thermoluminescence (TL). Deep trap states are reflected in a TL peak in the temperature region of 520 K, and are related to PSL. Shallow trap states reflected in the other TL peak at 250 K are related to afterglow. The intensity dependence of photoexcitation on PSL shows that carriers are more easily accumulated in the deep trap states than shallow trap states. Experiments of electron paramagnetic resonance are conducted to discuss the possible origins of PSL and the afterglow.
    研究論文(学術雑誌), 英語
  • Observation of infrared interband luminescence in magnesium by femtosecond spectroscopy
    Tohru Suemoto; Shota Ono; Akifumi Asahara; Tsuyoshi Okuno; Takeshi Suzuki; Kozo Okazaki; Shuntaro Tani; Yohei Kobayashi
    Journal of Applied Physics, 134巻, 掲載ページ 163105-1-163105-8, 出版日 2023年10月, 査読付
    研究論文(学術雑誌), 英語
  • 照明年報 第1章 光関連材料・デバイス 1.5 その他の光源材料・デバイス
    奥野剛史
    責任著者, 照明学会誌, 107巻, 5号, 掲載ページ 194-195, 出版日 2023年09月
    研究論文(大学,研究機関等紀要)
  • 東外大農工大電通大で開く3大学協働基礎ゼミ
    奥野剛史; 黒田立; 小泉憲裕; 小林義男
    筆頭著者, 電気通信大学紀要, 35巻, 1号, 掲載ページ 36-41, 出版日 2023年02月, 査読付
    研究論文(大学,研究機関等紀要), 日本語
  • Photostimulated luminescence excited by infrared LEDs in CaS:Eu2+ red afterglow phosphors
    Syota Yamaguchi; Yoriko Suda; Yasushi Nanai; Tsuyoshi Okuno
    ラスト(シニア)オーサー, Journal of Physics D: Applied Physics, IOP Publishing, 56巻, 1号, 掲載ページ 015301-015301, 出版日 2022年12月22日, 査読付, Abstract

    Red photostimulated luminescence (PSL) at 650 nm appears under the excitation by using an infrared (IR) light-emitting diode at 940 nm in CaS:Eu2+ afterglow phosphors. The effect of doping of Dy3+ ions, alkali metal ions or Cl ions in CaS:Eu2+ on afterglow or photostimulation is investigated. Afterglow temporal decays and thermoluminescence glow curves suggest that Dy3+ ions and alkali metal ions induce different types of defects in the phosphor, and enhance the afterglow independently. Doping of Cl ions is found to enhance the photostimulation by the IR excitation. Even if the phosphor is irradiated with IR light for some seconds, the afterglow decay curve is the same as when it is not irradiated with IR light. Trap states responsible for the photostimulation are different from those responsible for the afterglow. The red photostimulation appears under the excitation at 940 nm, after the phosphor is left in the dark for 60 min. Its intensity is 68% of the red PSL generated after being left in the dark for 10 min. It is considered that the PSL decreases little, when the sample is kept in the dark.
    研究論文(学術雑誌), 英語
  • 照明年報 第1章 光関連材料・デバイス 1.7 その他の光源材料・デバイス
    奥野剛史
    責任著者, 照明学会誌 Journal of the Illuminating Engineering Institute of Japan, 一般社団法人 照明学会, 106巻, 5号, 掲載ページ 207-207, 出版日 2022年09月01日
    研究論文(大学,研究機関等紀要), 日本語
  • 5年目を迎えたサイエンスカフェChofu
    奥野剛史; 君島龍太朗; 水戸和幸; 宮嵜武
    筆頭著者, 電気通信大学紀要 vol34, no1 (2022.2) pp.48-52, 34巻, 4号, 掲載ページ 48-52, 出版日 2022年02月, 査読付
    研究論文(大学,研究機関等紀要), 日本語
  • VBAとGASを用いたシフト表自動化アプリの作成とシフト組合せ最適化用の遺伝的アルゴリズムの検討
    富田一光; 佐藤寛之; 奥野剛史
    責任著者, 進化計算学会論文誌, 進化計算学会, 12巻, 3号, 掲載ページ 88-97, 出版日 2021年12月, 査読付
    研究論文(学術雑誌), 日本語
  • 照明年報 第1章 光関連材料・デバイス 1.7 その他の光源材料・デバイス
    奥野剛史
    責任著者, 照明学会誌 Journal of the Illuminating Engineering Institute of Japan, 一般社団法人 照明学会, 105巻, 5号, 掲載ページ 222-222, 出版日 2021年09月01日
    研究論文(学術雑誌), 日本語
  • Red afterglow and luminescence arising from defects in CaS:Eu2+,Tm3+
    Yoriko Suda; Yuki Tamura; Syota Yamaguchi; Yasushi Nanai; Tsuyoshi Okuno
    J. Phys. D: Appl. Phys., Institute of Physics, 54巻, 掲載ページ 415103(11pp), 出版日 2021年07月30日, 査読付, 700sの蓄光を生じる赤色残光蛍光体CaS:Eu2+,Tm3+において、母体CaSに起因する欠陥が残光の起源と考えられることを議論した。15Kおよび300Kにおけるナノ秒の時間分解発光スペクトルおよび寿命の測定を詳細に調べることによって、ナノ秒という光パルス励起直後のみにCaS母体欠陥からの青色発光が生じることを検出した。
    研究論文(学術雑誌), 英語
  • 東京都と電通大による高大連携:課題探究教室
    須田順子; 須子雅好; 奥野剛史; 中村仁; 鈴木勝
    大学の物理教育, 日本物理学会, 27巻, 2号, 掲載ページ 118-120, 出版日 2021年07月, 査読付
    研究論文(学術雑誌), 日本語
  • 青色励起赤色発光リン酸塩蛍光体の発光特性
    志村佳熙; 久島大輝; 田村祐樹; 奥野剛史
    映像情報メディア学会技術報告 ITE Technical Report, 一般社団法人 映像情報メディア学会, 45巻, 2号, 掲載ページ 33-36, 出版日 2021年01月
    研究論文(学術雑誌), 日本語
  • VBAとGASを用いたシフト表自動化アプリの作成とシフト組合せ最適化用の遺伝的アルゴリズムの検討
    富田一光; 奥野剛史
    第14回進化計算シンポジウム2020 講演論文集, 進化計算学会, 掲載ページ 101-106, 出版日 2020年12月
    研究論文(研究会,シンポジウム資料等), 日本語
  • 照明年報 第1章 光関連材料・デバイス 1.7 その他の光源材料・デバイス
    奥野剛史
    責任著者, 照明学会誌 Journal of the Illuminating Engineering Institute of Japan, 一般社団法人 照明学会, 104巻, 6号, 掲載ページ 265-266, 出版日 2020年09月
    研究論文(学術雑誌), 日本語
  • 新規固体光源のための光材料研究ー半導体、ナノ材料、蛍光体-
    奥野剛史
    責任著者, 照明学会誌 Journal of the Illuminating Engineering Institute of Japan, 一般社団法人 照明学会, 104巻, 3号, 掲載ページ 116-119, 出版日 2020年03月, 査読付
    研究論文(学術雑誌), 日本語
  • Red persistent luminescence excited by visible light in CaS:Eu2+,Tm3+
    Yuki Tamura; Tsuyoshi Okuno; Yoriko Suda; Yasushi Nanai
    Journal of Physics D: Applied Physics, 53巻, 掲載ページ 155101, 出版日 2020年02月, 査読付
    研究論文(学術雑誌), 英語
  • シリコン上に膜形成可能なシリコン硫化物蛍光体の研究
    中村裕貴; 青野瑞樹; 奥野剛史; 七井靖
    映像情報メディア学会技術報告 ITE Technical Report, 一般社団法人 映像情報メディア学会, 44巻, 1号, 掲載ページ 33-36, 出版日 2020年01月
    研究論文(学術雑誌), 日本語
  • 低速電子線励起用新規橙赤色硫化物蛍光体の開発
    奥野剛史; 中川康弘; 志村佳煕; 七井靖; 佐藤義孝; 御園生敏行
    信学技報 IEICE Technical Report, 一般社団法人 電子情報通信学会, EID2018-12(2019-01)巻, 掲載ページ 89-82, 出版日 2019年01月
    研究論文(学術雑誌), 日本語
  • ブレッドボードを用いた光通信実験の回路工作授業
    奥野剛史; 菅野敦史
    物理教育, 日本物理教育学会, 66巻, 3号, 掲載ページ 184-187, 出版日 2018年09月, 査読付
    研究論文(学術雑誌), 日本語
  • Broad luminescence of Ce3+ in multiple sites in (La,Ce,Y)6Si4S17
    Yasushi Nanai; Hayato Kamioka; Tsuyoshi Okuno
    Journal of Physics D: Applied Physics, Institute of Physics Publishing, 51巻, 13号, 掲載ページ 135103(8pp), 出版日 2018年03月08日, 査読付, We have developed novel broad luminescent phosphors (La,Ce,Y)6Si4S17 including multiple substituted sites of Ce3+ . They have formed a triclinic structure (P - 1) with three kinds of coordination structures around Ce3+ ions. The broad photoluminescence (PL) spectra at the range from 430 nm to 700 nm were observed, and they can be respectively decomposed into three PL bands. Moreover, the correlation between the three PL bands and the three substitution sites for Ce3+ was confirmed through the PL spectra at 78 K and Van Uitert's universal equation.
    研究論文(学術雑誌), 英語
  • Efficient host excitation in thiosilicate phosphors of lanthanide(III)-doped Y-4(SiS4)(3)
    Yasushi Nanai; Yousuke Suzuki; Tsuyoshi Okuno
    JOURNAL OF PHYSICS D-APPLIED PHYSICS, IOP PUBLISHING LTD, 49巻, 10号, 掲載ページ 105103(8pages), 出版日 2016年03月, 査読付, Lanthanide (Ln)-doped yttrium thiosilicate (Y1-x,Ln(x))(SiS4)(3) is synthesized, and its optical properties are studied. In (YI,Tb-x)(4)(SiS4)(3), the green photoluminescence band corresponding to the intra 4f transition of D-5(4) -> F-7(5) appears at 545 nm and becomes the maximum for x. = 02 in the range x = 0,01 to 1. The internal quantum efficiency is higher (11% for x = 0,01) for the thiosilicate host excitation (360nm) than for the direct excitation (1,6%) of the intra 4f transition of D-5(4) <- F-7(6) (489nm). A time -resolved photoluminescence study shows that the luminescence of defect states of thiosilicate hosts decays faster (typically 10-30 ns) for higher Tb3+ concentration x, In addition, the rise time of Tb3+ photoluminescence is shorter (10-40 ns) for greater x, Energy transfer from the thiosilicate host to Tb3+ is discussed using these results. For all of (Y1-x,-Ln(x))(4)(SiS4)(3) = 0.01, Ln = Pr, Nd, Dy, Er or Tin), the internal quantum efficiency is higher for the host excitation (11-21%) than for the direct excitation of intra 4f transitions (1,1-12%) A photoluminescence excitation study reveals broad host absorption in 300 100 tun for Ln luminescence. These results show the promising characteristics of the host absorption of (Y(1-x)Ln(x))(4)(SiS4)(3) phosphors and their optical properties.
    研究論文(学術雑誌), 英語
  • Effect of defects in TiO2 nanotube thin film on the photovoltaic properties of quantum dot-sensitized solar cells
    Masaya Akimoto; Taro Toyoda; Tsuyoshi Okuno; Shuji Hayase; Qing Shen
    THIN SOLID FILMS, ELSEVIER SCIENCE SA, 590巻, 掲載ページ 90-97, 出版日 2015年09月, 査読付, In the liquid-phase-deposition (LPD) method, the deposition temperature is considered to be one of the most important factors in TiO2 nanotube crystal growth. We investigated the effects of the deposition temperature on the surface morphology and defects in TiO2 nanotube (NT-TiO2) thin film electrodes utilizing scanning-electron-microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL), together with the effects of these on the photovoltaic characteristics of CdSe quantum dot (QD)-sensitized NT-TiO2 solar cells. In addition, we studied the effect of these defects on the physical properties, such as the carrier recombination and electron transport at the TiO2 and TiO2/QD interface. NT-TiO2 electrodes prepared at low temperatures have a more uniform surface and lower defects than those prepared at high temperatures. From the PL measurements and the photovoltaic characterization such as shunt resistance (R-sh) and open circuit voltage decay (OCVD), these defects can act as carrier recombination centers. The defect density increases with increasing deposition temperature, leading to an increase in carrier recombination. Series resistances (R-s) of the solar cells with NT-TiO2 electrodes prepared at high temperatures were larger than those of the solar cells with NT-TiO2 electrodes prepared at low temperatures, suggesting that the defects can also affect the carrier transport characteristics. Eventually, CdSe QD-sensitized NT-TiO2 solar cells employing NT-TiO2 prepared at low temperatures showed higher conversion efficiencies than those prepared at high temperatures. (C) 2015 Elsevier B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Crystal structure and photoluminescence of (Gd,Ce)(4)(SiS4)(3) and (Y,Ce)(4)(SiS4)(3)
    Yasushi Nanai; Katsuhiro Suzuki; Tsuyoshi Okuno
    MATERIALS RESEARCH EXPRESS, IOP PUBLISHING LTD, 2巻, 3号, 掲載ページ 036203(11pages), 出版日 2015年03月, 査読付, Structural and photoluminescence (PL) properties of undoped and Ce3+-doped rare-earth thiosilicate (Gd1-xCex)(4)(SiS4)(3) (0 <= x <= 0.1) and (Y1-xCex)(4)(SiS4)(3) (0 <= x <= 0.3) are reported. They maintain a monoclinic structure (P2(1)/n) for the whole range of x. Increases in lattice constants appear with the increase in x because of the replacement of Gd3+ and Y3+ by larger Ce3+. Yellow-orange PL originating from the 5d(1)-4f(1) (F-2(J), J = 5/2, 7/2) transition of Ce3+ is obtained. From the measurement of PL spectra at 20 K, red shifts of the peak wavelength with the increase in x would be understood by the change of relative intensity for two luminescent centers of Ce3+ in PL bands. The maximum internal quantum efficiency is 62% for (Y0.85Ce0.15)(4)(SiS4)(3). These phosphors have higher water-resistance than alkaline-earth metal thiosilicate phosphors such as Ba2SiS4.
    研究論文(学術雑誌), 英語
  • Electronic structures of two types of TiO2 electrodes: inverse opal and nanoparticulate cases
    Taro Toyoda; Witoon Yindeesuk; Tsuyoshi Okuno; Masaya Akimoto; Keita Kamiyama; Shuzi Hayase; Qing Shen
    RSC ADVANCES, ROYAL SOC CHEMISTRY, 5巻, 61号, 掲載ページ 49623-49632, 出版日 2015年, 査読付, We present a comparison between the electronic structures of inverse opal (IO) and nanoparticulate (NP)-TiO2 electrodes. The electronic structure details were obtained from optical absorption, fluorescence, and valence band studies in order to clarify the nature of the higher photovoltaic performance observed in sensitized solar cells using IO-TiO2 electrodes. We used photoacoustic (PA) and photoluminescence (PL) spectroscopy to characterize the optical absorption and fluorescence properties, respectively. Photoelectron yield (PY) spectroscopy was applied to characterize the position of the valence band maximum (VBM) of the IO- and NP-TiO2 electrodes. The PA spectrum for IO-TiO2 is different to that for NP-TiO2, indicating differences in the exciton-phonon interactions and the density of states in the conduction band. PL measurements showed that the curvature of the valence band structure of IO-TiO2 is different to that of NP-TiO2. Also, PL measurements showed that the oxygen vacancy in IO-TiO2 is different to that in NP-TiO2. Moreover, PY measurements showed VBM in IO-TiO2 to be at a higher position than that in NP-TiO2, suggesting a correlation with the increased open circuit voltage (V-oc) in sensitized solar cells.
    研究論文(学術雑誌), 英語
  • Correlation between photoluminescence and structure in silicon nanowires fabricated by metal-assisted etching
    Kotaro Oda; Yasushi Nanai; Toshiyuki Sato; Seiji Kimura; Tsuyoshi Okuno
    PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, WILEY-V C H VERLAG GMBH, 211巻, 4号, 掲載ページ 848-855, 出版日 2014年04月, 査読付, Structural and optical properties of silicon nanowires synthesized by metal-assisted chemical etching are investigated. Macroscopic properties of nanowire arrays as well as microscopic photoluminescence (PL) and Raman scattering spectra of single nanowires are studied. The morphology of silicon nanowires changes depending on etching duration and concentration of H2O2 in the etching solution. In thick nanowires having small length and large diameter, red PL appears. Typical length and diameter are 90m and 600nm, respectively. The PL spectrum is composed of two bands with the peaks at 635 and 705nm. In thin nanowires having large length and small diameter with their ratio larger than 210, no PL appears. Clear correlation between the morphology of nanowires and the PL appearance is demonstrated. Transmission electron microscopy reveals the presence of porous structures of silicon at the top of nanowires. In the middle part of nanowires, the interface between silicon crystalline core and surrounding silicon oxide is smooth and no nanocrystal is present. Optical Raman microscopy for a single nanowire with the space resolution of approximate to 1m clarifies positions where the red PL appears. At the top of nanowires where porous structures of silicon are present, the red PL appears. At these positions, the Raman peak of the optical phonon mode of crystalline silicon becomes broad and shifted. These Raman spectra reflect silicon nanocrystals present at the top of the nanowire. The origin of the red PL in silicon nanowires is considered to be silicon nanocrystals present at the top of nanowires.
    研究論文(学術雑誌), 英語
  • Glycothermal synthesis and photoluminescent properties of Ce3+-doped YBO3 mesocrystals
    Hiroki Hara; Satoru Takeshita; Tetsuhiko Isobe; Yasushi Nanai; Tsuyoshi Okuno; Tomohiro Sawayama; Seiji Niikura
    JOURNAL OF ALLOYS AND COMPOUNDS, ELSEVIER SCIENCE SA, 577巻, 掲載ページ 320-326, 出版日 2013年11月, 査読付, We report a glycothermal synthesis of Ce3+-doped YBO3 mesocrystals and their Ce3+-concentration dependence of particulate and photoluminescent properties. Submicrometer-sized YBO3:Ce3+ disk-like particles with Ce3+ concentrations of 0-3 at.% were formed from trimethyl borate and acetates of yttrium and cerium(III) via a glycothermal reaction at 300 degrees C for 2 h in 1,4-butanediol. The size of the particles decreased from similar to 1.5 mu m to similar to 150 nm with increasing the Ce3+ concentration up to 1 at.%. Selected area electron diffraction revealed that each disk-like particle was a mesoaystal, i.e., an assembly of nanocrystals with a uniform crystallographic orientation, irrespective of the Ce3+ concentration. The particles showed blue emission through 5d-4f transitions of Ce3+ under near-UV excitation. Concentration quenching of the Ce3+ emission for the glycothermally-prepared YBO3:Ce3+ started from a lower Ce3+ concentration than that of solid-state-prepared bulk YBO3:Ce3+, indicating an inhomogeneous distribution of Ce3+ ions in the mesocrystals. (C) 2013 Elsevier B.V. All rights
    研究論文(学術雑誌), 英語
  • Luminescence Properties of Rare-Earth-Doped Thiosilicate Phosphors on Silicon Substrate
    Yasushi Nanai; Yu Sakamoto; Tsuyoshi Okuno
    JAPANESE JOURNAL OF APPLIED PHYSICS, IOP PUBLISHING LTD, 52巻, 4号, 掲載ページ 04CG15(5pages), 出版日 2013年04月, 査読付, The luminescence properties of rare-earth-doped thiosilicate phosphors are reported. These thiosilicate materials are fabricated in phosphor layers on silicon substrates. For Eu2+-doped calcium thiosilicate, yellow (560 nm) and red (650 nm) bands are obtained in the photoluminescence spectrum, which is almost the same as that for the corresponding powder sample. The energy transfer efficiency from Eu2+ to Er3+ in Eu2SiS4:Er3+ on Si substrates is improved by optimization of the annealing conditions. In addition, the insulation of electroluminescence devices using BaSi2S5:Eu2+ on silicon-on-insulator substrates is improved using a high-dielectric-constant polymer as a transparent insulating layer. (C) 2013 The Japan Society of Applied Physics
    研究論文(学術雑誌), 英語
  • 先進理工学科における2年次専門実験(電気・電子回路実験)の準備と実施について
    奥野剛史; 大家明広; 山崎典昌; 高橋光生; 早川義彦; 矢崎和幸; 和田紀子; 藁科崇; 坂本克好; Choo Cheow Keong; 永井豊; 守屋雅隆; 沈青; 島田宏; 林茂雄
    電気通信大学紀要 vol25, no1 (2013.2) pp.73-78, 電気通信大学, 25巻, 1号, 掲載ページ 73-78, 出版日 2013年02月, 査読付, The new laboratory class of Electric and Electronic Circuit Laboratory has been conducted. All of the second year students at the Department of gineering Science are required to take this class. An example of preparation for new classes in the new department is shown. Academic engineers and faculties formerly belonging to dif ferent depar tments are cooperatively involved in the preparation and teaching for the laboratory class. The class has been successfully completed in 2011 for the first time after the reorganization of the Faculty of Informatics and Engineering in April 2010. The results concerning report scores of students, answers of students' questionnaires, and e-Learning are shown and discussed.
    研究論文(大学,研究機関等紀要), 日本語
  • Red luminescence of Eu3+ doped ZnO nanoparticles fabricated by laser ablation in aquepus solution
    K. Katsuki; T. Sato; R. Suzuki; Y. Nanai; S. Kimura; T. Okuno
    Applied Physics A, 108巻, 掲載ページ 321-327, 出版日 2012年07月, 査読付
    研究論文(学術雑誌), 英語
  • Crystal structure, photoluminescence and electroluminescence of (Ba,Eu)Si2S5
    Y. Nanai; Y. Sakamoto; T. Okuno
    Journal of Physics D: Applied Physics, 45巻, 掲載ページ 265102(8pages), 出版日 2012年06月, 査読付
    研究論文(学術雑誌), 英語
  • Fabrication of ZnO nanoparticles by laser ablation of sintered ZnO in aquepus solution
    K. Kawabata; Y. Nanai; S. Kimura; T. Okuno
    Applied Physics A, 107巻, 掲載ページ 213-220, 出版日 2012年01月, 査読付
    研究論文(学術雑誌), 英語
  • 赤外線リモコン受信モジュールを用いた赤外線検出器
    奥野剛史; 中村仁; 鈴木勝
    物理教育, 日本物理教育学会, 59巻, 2号, 掲載ページ 120-121, 出版日 2011年06月, 査読付
    研究論文(学術雑誌), 日本語
  • Photoluminescence properties of erbium-doped europium thiosilicate
    Mitsuharu Sugiyama; Yasushi Nanai; Yuu Okada; Tsuyoshi Okuno
    JOURNAL OF PHYSICS D-APPLIED PHYSICS, IOP PUBLISHING LTD, 44巻, 9号, 掲載ページ 095404(5pages), 出版日 2011年03月, 査読付, Photoluminescence properties of erbium-doped europium thiosilicate (Eu(2)SiS(4) : Er) are reported. The material is fabricated in powder and on silicon substrates. The luminescence at 1.54 mu m corresponding to the (4)I(13/2)-(4)I(15/2) transition of Er(3+) is observed. Broad absorption of the 4f(7)-4f(6)5d transition of Eu(2+) in the host matrix in 350-500 nm region is used for the excitation of Er(3+). Efficient energy transfer from the host to erbium is realized.
    研究論文(学術雑誌), 英語
  • Crystal structure and optical properties of (Ba,Eu)2SiS 4
    Yasushi Nanai; Chiharu Sasaki; Yu Sakamoto; Tsuyoshi Okuno
    Journal of Physics D: Applied Physics, 44巻, 40号, 掲載ページ 405402(6pages), 出版日 2011年, 査読付, Structural and optical properties of europium-doped barium thiosilicate are reported. The whole range of the Eu concentration x in Ba 2(1-x)Eu2xSiS4 is studied. The lattice constants continuously decrease with the increase in x in the orthorhombic (0 ≤ x ≤ 0.6) or in the monoclinic (0.7 ≤ x ≤ 1) structures. This decrease changes the strength of the crystal field for Eu2+ and thus shifts the wavelength of photoluminescence (PL) (490-570 nm). For Eu-doped Ba2SiS4 (x = 0.01 and 0.02), the PL efficiency is 40%, and the decay time of its single exponential profile is obtained to be 240 ns. The decrease in the PL efficiency and the change in the decay profile (0.05 ≤ x ≤ 0.9) are explained by the enhancement of the cross relaxation among Eu 2+ ions. © 2011 IOP Publishing Ltd.
    研究論文(学術雑誌), 英語
  • Optical Properties of Silicon Nanowires Fabricated by Electroless Silver Deposition
    Satoru Toda; Tetsuji Oishi; Takuma Yoshioka; Tsuyoshi Okuno
    JAPANESE JOURNAL OF APPLIED PHYSICS, IOP PUBLISHING LTD, 49巻, 9号, 掲載ページ 095002-1-7, 出版日 2010年, 査読付, Vertically aligned silicon nanowires are fabricated on silicon substrates by electroless silver deposition, and their optical properties are investigated. The diameter of the nanowires ranges from 100 to 500 nm and their length ranges from 30 to 100 mm. Red photoluminescence appears at approximately 700 nm at room temperature. Its peak and intensity vary along the wire positions in Raman microscopy measurements. The photoluminescence intensity is high at the top of the wire. In this region, oxidation is enhanced and the Raman scattering spectra of the optical phonon mode tend to be broadened. The origin of the red photoluminescence is assumed to be defect states located at the interface between the core of the silicon nanowires and the surrounding silicon oxide. (C) 2010 The Japan Society of Applied Physics
    研究論文(学術雑誌), 英語
  • Effective Inclusion of e-Learning in a Subject of Physics Experiments: Introductory Electronics Laboratory
    T. Okuno; K. Abe; N. Yamazaki; A. Ooe; K. Igarashi; S. Hayashi; M. Suzuki
    INTERNATIONAL CONFERENCE ON PHYSICS EDUCATION, AMER INST PHYSICS, 1263巻, 掲載ページ 130-+, 出版日 2010年, 査読付, A Web-based e-Learning homework system was introduced in the undergraduate subject of the introductory electronics experiment; "Introductory Electronics Laboratory". This homework is appended to practical trainings and face-to-face guidance in the laboratory (blended-type e-Learning). The e-Learning is mainly prepared to teach basic electronics and to guide necessary apparatus before the practical training. The overall impression about this subject in students' questionnaires has improved from 3.5 for 2005/2006 (e-Learning not introduced) to 3.9 2007/2008 (e-Learning introduced) (5 for good, 3 for average, and 1 for bad). Students' understanding of the experiments has also improved from 3.43 for 2005/2006 to 3.45 for 2007/2008 (5, 4, 3, 2 for S, A, B, C grade). This subject is compulsory for all second-year students in our department (similar to 120 students). The e-Learning system in our case is considered to be effective especially for required subjects of experiments and large classes.
    研究論文(国際会議プロシーディングス), 英語
  • Yellow Photoluminescence of Europium Thiosilicate on Silicon Substrate
    Masumi Nishimura; Yasushi Nanai; Takayuki Bohda; Tsuyoshi Okuno
    JAPANESE JOURNAL OF APPLIED PHYSICS, JAPAN SOCIETY APPLIED PHYSICS, 48巻, 7号, 掲載ページ 072301-1-4, 出版日 2009年07月, 査読付, We report the fabrication of europium thiosilicate (Eu(2)SiS(4)) on a silicon substrate. Europium sulfide (EuS) is thermally evaporated on a silicon substrate. It is sealed in a vacuum with sulfur and then heated at 650 degrees C. Eu(2)SiS(4) shows intense yellow photoluminescence, and its wavelength (peak 570 nm) and width (60 nm) are reproducible. This corresponds to the 4f(6)5d-4f(7) transition of Eu(2+). The photoluminescence efficiency of Eu(2)SiS(4) is measured and estimated to be 0.5%. (C) 2009 The Japan Society of Applied Physics DOI: 10.1143/JJAP.48.072301
    研究論文(学術雑誌), 英語
  • 電子回路学実験(量子・物質工学科)におけるeラーニング実施について
    奥野剛史; 阿部浩二; 山崎典昌; 大家明広; 五十嵐清; 林茂雄
    電気通信大学紀要 vol21, no1&2 (2009.1) pp.59-66, 電気通信大学, 21巻, 1&2号, 掲載ページ 59-66, 出版日 2009年01月, 査読付, We have started e-Learning homework system in Introductory Electronics Laboratory at theDepartment of Applied Physics and Chemistry. WebClass in the Center for Developing e-Learningis used. Students are required to do this e-Learning homework before doing electronicsexperiments in the laboratory class. They would acquire basic knowledge on each theme of theexperiment every two weeks. This e-Learning homework system seemed to be effective andinterest most of the students. This is one of the subjects in "Learning support project for coresubjects by using Student Cards." This is also an example showing WebClass system from a user.
    研究論文(大学,研究機関等紀要), 日本語
  • Photoluminescence properties of Eu3+-doped ZnO nanoneedles
    Katsuyuki Ebisawa; Tsuyoshi Okuno; Kohji Abe
    JAPANESE JOURNAL OF APPLIED PHYSICS, JAPAN SOC APPLIED PHYSICS, 47巻, 9号, 掲載ページ 7236-7238, 出版日 2008年09月, 査読付, Eu3+-doped ZnO nanoneedles were fabricated by thermal evaporation. In order to include Eu in ZnO nanostructures, europium nitrate was used to produce starting droplets from which ZnO nanoneedles were grown. Photoluminescence spectra included a sharp blue peak corresponding to the ZnO band gap and a broad red band due to defect states. In addition, sharp intra-4f transitions of Eu3+ ions were observed. Energy transfer from the ZnO matrix to Eu3+ was also observed. Study of the photoluminescence excitation revealed absorption tail states below the ZnO band gap induced by the inclusion of Eu ions in the ZnO nanoneedles. The location of Eu ions was assumed to be near the surfaces of the ZnO nanoneedles.
    研究論文(学術雑誌), 英語
  • Intense green luminescence from Eu2+ -doped ZnO microstructures
    Hideo Sugimoto; Katsuyuki Ebisawa; Tsuyoshi Okuno
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS, INST PURE APPLIED PHYSICS, 46巻, 33-35号, 掲載ページ L839-L841, 出版日 2007年09月, 査読付, We fabricated Eu2+-doped ZnO microstructures by thermal evaporation. Their structures were micrometer-size grains with smooth surfaces or nanometer-size needles. Morphology depended on the temperature region where structures were grown. A strong green luminescence at room temperature is demonstrated. This is attributed to the efficient energy transfer from the ZnO matrix to Eu2+ ions and their 5d-4f transitions.
    研究論文(学術雑誌), 英語
  • Optical spin polarization and exchange interaction in doubly charged InAs self-assembled quantum dots
    VK Kalevich; IA Merkulov; AY Shiryaev; KV Kavokin; M Ikezawa; T Okuno; PN Brunkov; AE Zhukov; VM Ustinov; Y Masumoto
    PHYSICAL REVIEW B, AMERICAN PHYSICAL SOC, 72巻, 4号, 掲載ページ 045325-1-8, 出版日 2005年07月, 査読付, The work is an experimental study of optical spin polarization in InAs/GaAs quantum dots (QDs) with two resident electrons or holes. A capture of a photogenerated electron-hole pair into such a QD creates a negative or positive tetron (doubly charged exciton). Spin polarization was registered by the circular polarization of the QD photoluminescence (PL). The spin state was found to be radically different in the dots with the opposite sign of the charge. Particularly, under excitation in a GaAs barrier, the polarization of the ground-state PL is negative (relative to the polarization of exciting light) in the negatively charged QDs and positive in the positively charged QDs. With increasing excitation intensity, the negative polarization rises from zero up to a saturation level, while the positive polarization decreases. The negative polarization increases in weak magnetic fields applied in Faraday geometry; however, it is suppressed in strong fields. The positive polarization always increases as a function of magnetic field. We propose a theoretical model that qualitatively explains the experimental results.
    研究論文(学術雑誌), 英語
  • Crosshatch observation in MBE-grown be-doped InGaAs epilayer on InP
    H Bando; M Kosuge; K Ban; H Yoshino; R Takahashi; H Okamoto; T Okuno; Y Masumoto
    JOURNAL OF CRYSTAL GROWTH, ELSEVIER SCIENCE BV, 278巻, 1-4号, 掲載ページ 610-613, 出版日 2005年05月, 査読付, Misfit dislocation was investigated by observing crosshatch over surfaces of InxGa1-xAs-In0.52Al0.48As strained multiple quantum wells (MQWs) and InxGa1-xAs bulk-like thin epifilms grown on InP substrates. It was found that no crosshatch was observed on surfaces of non-doped InxGa1-xAs-In0.52Al0.48As strained MQW over an In composition range of 0.32 < x < 0.78 and that Be-doped InxGa1-xAs bulk-like thin films were also crosshatch free over a wide range of 0.42 < x &LE; 1.0, which clearly exceeds the critical thickness limit. Surface and cross-sectional diagnostics and a preliminary result on the electron mobility of the crosshatch-free InAs bulk-like thin films were presented. © 2005 Elsevier B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Optical spin polarization in double charged InAs self-assembled quantum dots
    VK Kalevich; IA Merkulov; AY Shiryaev; KV Kavokin; M Ikezawa; T Okuno; PN Brunkov; AE Zhukov; VM Ustinov; Y Masumoto
    PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, WILEY-V C H VERLAG GMBH, 202巻, 3号, 掲載ページ 387-391, 出版日 2005年02月, 査読付, The work is an experimental study of optical spin polarization in InAs/GaAs quantum dots (QDs) with 2 resident electrons or holes. A capture of a photo-generated electron-hole pair into such a QD creates a negative or positive tetron (double-charged exciton). Spin polarization was registered by the circular polarization of the QD photoluminescence (PL). The spin state was found to differ radically in the dots with opposite in sign charge. Particularly, under excitation in a GaAs barrier, the ground state PL polarization is negative (relative to the polarization of an exciting light) in the negatively charged QDs and positive in the positively charged QDs. With increasing excitation intensity, the negative polarization rises from zero up to a saturation level, while the positive polarization decreases. The negative polarization increases in weak magnetic fields applied in Faraday geometry, but strong fields suppress it. The positive polarization always increases as a function of magnetic field. We propose a theoretical model that qualitatively explains the experimental results.
    研究論文(学術雑誌), 英語
  • Spin relaxation in CdTe quantum dots
    Y Chen; T Okuno; Y Masumoto; Y Terai; S Kuroda; K Takita
    PHYSICAL REVIEW B, AMER PHYSICAL SOC, 71巻, 3号, 掲載ページ 033314-1-4, 出版日 2005年01月, 査読付, We have measured photoluminescence (PL) spectra and time-resolved PL in CdTe quantum dots under the longitudinal magnetic field up to 10 T. Circular polarization of PL increases with increasing magnetic field, while its linear polarization remains zero under linearly polarized excitation. This behavior cannot be explained by the anisotropic exchange interaction of excitons. Time-resolved PL measurements clarified that this behavior is caused by the suppression of spin relaxation induced by the longitudinal magnetic field. We believe that this behavior is related to the hyperfine interaction of electron spin with magnetic momenta of lattice nuclei.
    研究論文(学術雑誌), 英語
  • Absorption saturation energy density of InGaAs-InAIAs multiple quantum well under tensile and compressive strain
    T Okuno; Y Masumoto; A Higuchi; H Yoshino; H Bando; H Okamoto
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS, INST PURE APPLIED PHYSICS, 44巻, 16-19号, 掲載ページ L558-L560, 出版日 2005年, 査読付, Optical absorption saturation density I-s was measured for InxGa1-xAs-In0.52Al0.48As multiple quantum well structures grown on InP (100) substrates by molecular beam epitaxy. Indium composition x was varied from 0.32 to 0.70 so that the quantum well layer was under tensile strain (x < 0.53), lattice matched (x = 0.53), or compressive strain (x > 0.53). Optical measurement was carried out using femtosecond light pulses from the optical parametric amplifier of a mode-locked Ti-sapphire laser amplifier. The density I-s in a sample changed as a function of photon energy and exhibited a minimum value at the band-edge exciton energy. This minimum, showed the smallest value at x = 0.46 (under tensile strain) of all the samples with different x. This was in marked contrast to the results reported in the literature. Degenerate pump-probe measurement was also carried out, and the results showed that the relative transmission change Delta T/T measured at zero delay between the pump and probe pulses exhibited the largest value at x = 0.46, confirming the result of I-s measurement.
    研究論文(学術雑誌), 英語
  • Indirect optical absorption of single crystalline beta-FeSi2
    H. Udono; I. Kikuma; T. Okuno; Y. Masumoto; H. Tajima
    Applied Physics Letters, 85巻, 11号, 掲載ページ 1937-1939, 出版日 2004年09月, 査読付
    研究論文(学術雑誌), 英語
  • Optical properties of beta-FeSi2 single crystals grown from solutions
    H Udono; Kikuma, I; T Okuno; Y Masumoto; H Tajima; S Komuro
    THIN SOLID FILMS, ELSEVIER SCIENCE SA, 461巻, 1号, 掲載ページ 182-187, 出版日 2004年08月, 査読付, We studied the optical absorption, polarized reflectance (PR) and photoluminescence (PL) of beta-FeSi2 single crystals grown from solution. In low-absorption measurements, we found a phonon emission and absorption structure, which suggests an indirect transition. The exciton energy gap of 0.814 eV was determined from the absorption spectrum at 3.5 K. We also found a direct transition with the gap energy of 0.939 eV. PR measurements for E//a, E//b and E//c revealed the anisotropy of reflectivity of beta-FeSi2. We observed the PL with a peak wavelength of about 1.56 mum at 20 K. (C) 2004 Elsevier B.V All rights reserved.
    研究論文(学術雑誌), 英語
  • Quantum beats in semiconductor quantum dots
    Y Masumoto; Ignatiev, IV; K Nishibayashi; T Okuno; SY Verbin; IA Yugova
    JOURNAL OF LUMINESCENCE, ELSEVIER SCIENCE BV, 108巻, 1-4号, 掲載ページ 177-180, 出版日 2004年06月, 査読付, This paper reports observation of four kinds of luminescence quantum beats (QBs) in semiconductor quantum dots (QDs). QBs of Zeeman-split bright heavy-hole excitons under a longitudinal magnetic field and QBs coming from the electron spin Larmor precession under a transverse magnetic field were observed for strain-induced GaAs QDs. Another type of QB between bright and dark heavy-hole excitons was observed in neutralized self-assembled InP QDs in a tilted magnetic field. Trionic QBs were observed in negatively charged InP QDs possessing only one excess electron in the absence of the magnetic field. Analysis of QBs gives us fine energy splittings of exchange energy and Zeeman splittings of exciton. electron and hole with an accuracy of 10 mueV despite the broad inhomogeneous linewidth of 20-50 meV. (C) 2004 Elsevier B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Quantum beats in semiconductor quantum dots
    Y Masumoto; Ignatiev, IV; K Nishibayashi; T Okuno; SY Verbin; IA Yugova
    JOURNAL OF LUMINESCENCE, ELSEVIER SCIENCE BV, 108巻, 1-4号, 掲載ページ 177-180, 出版日 2004年06月, 査読付, This paper reports observation of four kinds of luminescence quantum beats (QBs) in semiconductor quantum dots (QDs). QBs of Zeeman-split bright heavy-hole excitons under a longitudinal magnetic field and QBs coming from the electron spin Larmor precession under a transverse magnetic field were observed for strain-induced GaAs QDs. Another type of QB between bright and dark heavy-hole excitons was observed in neutralized self-assembled InP QDs in a tilted magnetic field. Trionic QBs were observed in negatively charged InP QDs possessing only one excess electron in the absence of the magnetic field. Analysis of QBs gives us fine energy splittings of exchange energy and Zeeman splittings of exciton. electron and hole with an accuracy of 10 mueV despite the broad inhomogeneous linewidth of 20-50 meV. (C) 2004 Elsevier B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • MBE growth and optical properties of self-organized dots of CdTe and (Cd,Mn)Te
    S Kuroda; N Itoh; Y Terai; K Takita; T Okuno; M Nomura; Y Masumoto
    JOURNAL OF ALLOYS AND COMPOUNDS, ELSEVIER SCIENCE SA, 371巻, 1-2号, 掲載ページ 31-36, 出版日 2004年05月, 査読付, MBE growth of self-organized dots of CdTe and (Cd,Mn)Te on the lattice-mismatched ZnTe surface and their optical properties are reported. The formation of nano-scale dots was confirmed when CdTe or Cd1-xMnxTe with the Mn composition x less than or equal to 0.1 was deposited on the ZnTe (001) surface beyond the critical thickness of 1.5-2 monolayers (MLs). In the PL measurement on CdTe dots, the zero-dimensional (OD) excitonic luminescence from the dots was observed. Though the emission from the wetting layer was not observed in the PL spectra, the existence of the wetting layer state was confirmed in the PLE measurement. The PL spectra from (Cd,Mn)Te dots were split into two lines in low temperatures less than 20 K. The lower-energy line showed anomalous behaviors in the dependences on temperature and magnetic field. This is considered due to the magnetic polaron effect enhanced by the OD confinement. (C) 2003 Elsevier B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Optical spin polarization of holes in negatively charged InAs/GaAs self-assembled quantum dots
    VK Kalevich; M Ikezawa; T Okuno; KV Kavokin; AY Shiryaev; PN Brunkov; AE Zhukov; VM Ustinov; Y Masumoto
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, ELSEVIER SCIENCE BV, 21巻, 2-4号, 掲載ページ 1018-1021, 出版日 2004年03月, 査読付, We report an observation of the optical polarization of hole spins in the negatively charged self-assembled InAs/GaAs quantum dots when the dot is occupied by 2 or 5 electrons on average. It was found that the spin relaxation time of holes is comparable with their lifetime. It was demonstrated that the hole spin polarization can be destroyed by both the transverse magnetic field (the Hanle effect) and the electric bias. (C) 2003 Elsevier B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Optical spin polarization in negatively charged InAs self-assembled quantum dots under applied electric field
    VK Kalevich; M Ikezawa; T Okuno; AY Shiryaev; AE Zhukov; VM Ustinov; PN Brunkov; Y Masumoto
    PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, WILEY-V C H VERLAG GMBH, 238巻, 2号, 掲載ページ 250-253, 出版日 2003年07月, We have studied the influence of an external electric field on the optical spin polarization of initially negatively charged InAs/GaAs quantum dots (QDs). The spin polarization of the carriers was controlled by measuring the photoluminescence (PL) circular polarization. We have found that the PL polarization of the QD is negative under an excitation above the GaAs barrier, and that it becomes positive under an excitation below the barrier. An applied negative electric field destroys both positive and negative polarization. The time decay of the negative polarization was found from time-resolved measurements to exceed strongly the QD radiative lifetime. This fact indicates a long-living spin memory in the dots under study.
    研究論文(学術雑誌), 英語
  • Luminescence quantum beats of strain-induced GaAs quantum dots
    K Nishibayashi; T Okuno; Y Masumoto; HW Ren
    PHYSICAL REVIEW B, AMERICAN PHYSICAL SOC, 68巻, 3号, 掲載ページ 035333-1-6, 出版日 2003年07月, Quantum beats of the strain-induced GaAs quantum dots were observed in the time-resolved photoluminescence in the magnetic field parallel and perpendicular to the growth direction. Quantum beats observed under the longitudinal magnetic field are caused by quantum interference of bright excitons showing Zeeman splitting. The oscillation period depends on the angle between the growth direction of the crystal and the magnetic field. Analysis based on the spin Hamiltonian for excitons explains the observed data and gives g factors 0.51, 0.17, and 0.34 to the exciton, electron, and heavy hole, respectively. Quantum beats coming from electron Larmor precession were observed under the transverse magnetic field. The isotropic electron g factor is observed in contrast to the anisotropic electron g factor for the corresponding quantum well and is ascribed to the strain-induced opposite energy shift of heavy- and light-hole bands.
    研究論文(学術雑誌), 英語
  • Spin quantum beats in charged and neutral InP quantum dots
    Ignatiev, IV; T Okuno; SY Verbin; IA Yugova; Y Masumoto
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, ELSEVIER SCIENCE BV, 17巻, 1-4号, 掲載ページ 365-366, 出版日 2003年04月, We report on several types of quantum beats observed in the photoluminescence kinetics of InP self-assembled quantum dots (QDs) in a magnetic field. It is shown that the charge state of the QDs crucially affects the possibility to observe the beats. (C) 2002 Elsevier Science B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • 1.5-mu m intraband transitions in PbSe quantum dots
    T Okuno; M Ikezawa; Y Masumoto; GR Hayes; B Deveaud; AA Lipovskii
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS, INST PURE APPLIED PHYSICS, 42巻, 2A号, 掲載ページ L123-L125, 出版日 2003年02月, 査読付, Intraband transitions around 1.5 mum are studied in PbSe quantum dots at room temperature. Femtosecond pump-probe measurements reveal induced absorption by photoexcited carriers up to higher energy levels and its relaxation. A dominant decay component has a decay time of 10-40 ps, which is determined by the relaxation of carriers at the lowest absorption peak. The induced absorption is observed in a broad spectral range between 0.77 and 2.5 eV.
    研究論文(学術雑誌), 英語
  • Highest-order optical phonon-mediated relaxation in CdTe/ZnTe quantum dots(jointly worked)
    Journal of Luminescence, 102-103巻, 掲載ページ 623-628, 出版日 2003年
    英語
  • Spin relaxation in InP quantum dots
    Y Masumoto; Gerlovin, I; M Ikezawa; Ignatiev, I; T Okuno; S Verbin; Yugova, I
    2ND INTERNATIONAL CONFERENCE ON SEMICONDUCTOR QUANTUM DOTS, WILEY-VCH, INC, 0巻, 掲載ページ 1368-1371, 出版日 2003年, 査読付, Spin dynamics in the self-assembled InP quantum dots is studied experimentally. The spin coherence relaxation is analyzed by studying two types of quantum beats observed in photoluminescence kinetics in an external magnetic field. It is found that the spin coherency in the quantum dots rapidly decays due to the reversible phase relaxation related to a spread of the exchange and Zeeman splittings of the electron-hole levels.
    研究論文(国際会議プロシーディングス), 英語
  • Optical Study of Phonon-Mediated Carrier Relaxation in CdTe/ZnTe Self-Assembled Quantum Dots
    Tsuyoshi Okuno; Mitsuhiro Nomura; Yasuaki Masumoto; Yoshikazu Terai; Shinji Kuroda; Kôki Takita
    Journal of the Physical Society of Japan, 71巻, 12号, 掲載ページ 3052-3058, 出版日 2002年12月, 査読付, We report the photoluminescence and excitation spectra of CdTe self-assembled quantum dots grown by molecular beam epitaxy in ZnTe. In photoluminescence excitation spectra, multiple longitudinal-optical (LO) phonon structures up to the 19th order are observed even above ZnTe-matrix energy, and the wetting layer was clarified. Photoluminescence spectra of CdTe quantum dots having LO phonon structures under quasi-resonant excitation show that CdTe dots are surrounded by ZnxCd1-xTe (x ∼ 0.8, where x ranges from 0.5 to 1). Phonon-mediated carrier relaxation is discussed. Photoexcited carriers forming excitons are relaxed by emitting multiple LO phonons of the ZnTe matrix successively from the higher energy state of the matrix to the wetting layer. At the wetting layer, involved LO phonons are transformed to those of ZnxCd1-xTe surrounding the CdTe dots. ZnTe-like and CdTe-like LO phonons and, lastly, acoustic phonons, are emitted in relaxation to the CdTe-dot state.
    研究論文(学術雑誌), 英語
  • PbSe量子ドットの光物性
    池沢, 道男; 奥野, 剛史; 舛本, 泰章; A.A.Lipovskii
    ナノ学会会報, ナノ学会, 1巻, 1号, 掲載ページ 27-32, 出版日 2002年10月
    研究論文(その他学術会議資料等), 日本語
  • Ultrafast and wideband response in optical nonlinearity of molecular-beam-epitaxy-grown GaAs
    T Okuno; Y Masumoto; S Kadono; S Kitade; H Bando; H Okamoto
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS, INST PURE APPLIED PHYSICS, 41巻, 7A号, 掲載ページ L745-L747, 出版日 2002年07月, 査読付, In order to obtain ultrafast responses with no additional slow component, we have investigated optical nonlinearity in molecular-beam-epitaxy(MBE)-grown GaAs at various excitation wavelengths L The slow response component decreases in magnitude and almost disappears when undoped GaAs is excited deep inside the energy band of GaAs. For beryllium-doped low-temperature-grown GaAs, fast responses of less than I ps response time with a negligible slow component are obtained from the bandedge to 230 meV or more above it. Measurement of saturation energy density I, of the optical absorption shows that the increase in I-s at lambda = 780 nm as compared to I, at the bandedge is only by a factor of 3-4 for undoped GaAs and it is very small for beryllium-doped low-temperature MBE-grown GaAs.
    研究論文(学術雑誌), 英語
  • Complementary detection of confined acoustic phonons in quantum dots by coherent phonon measurement and Raman scattering
    M Ikezawa; T Okuno; Y Masumoto; AA Lipovskii
    PHYSICAL REVIEW B, AMER PHYSICAL SOC, 64巻, 20号, 掲載ページ / 201315-1-4, 出版日 2001年11月, Coherent acoustic phonon oscillation is observed in PbSe quantum dots embedded in phosphate glass by femtosecond pump-and-probe. The size dependence of the oscillation is investigated. Distinct low-frequency peaks are observed in Raman spectrum for the same samples. The size-dependence of the frequencies is well explained by elastic sphere model, but the observed modes are different to each other for coherent phonon and Raman scattering. Coherent phonon measurement and Raman scattering are found to give complementary information on confined acoustic phonons in this system.
    研究論文(学術雑誌), 英語
  • Femtosecond response time in beryllium-doped low-temperature-grown GaAs/AlAs multiple quantum wells
    T Okuno; Y Masumoto; Y Sakuma; Y Hayasaki; H Okamoto
    APPLIED PHYSICS LETTERS, AMER INST PHYSICS, 79巻, 6号, 掲載ページ 764-766, 出版日 2001年08月, 査読付, We have investigated optical nonlinearity in beryllium-doped low-temperature (LT) molecular-beam-epitaxy-grown GaAs/AlAs multiple quantum wells (MQWs). The response time of the nonlinearity is reduced by Be doping in the MQW. While the undoped LT MQW shows a 0.7-0.9 ps response, the response time of the Be-doped LT MQW is as short as 0.25 ps. The saturation density of the Be-doped MQW is almost the same as that of the undoped MQW, and is smaller than that of bulk GaAs. These results demonstrate that the Be-doped LT MQW exhibits a faster response than the undoped LT MQW, and a faster response as well as larger nonlinearity than LT bulk GaAs. (C) 2001 American Institute of Physics.
    研究論文(学術雑誌), 英語
  • Optical study of strain-induced GaAs quantum dots
    K Nishibayashi; T Okuno; T Mishina; S Sugou; HW Ren; Y Masumoto
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, INST PURE APPLIED PHYSICS, 40巻, 3B号, 掲載ページ 2084-2086, 出版日 2001年03月, The excitation-intensity-dependent nonlinear luminescence as well as the luminescence of strain-induced GaAs quantum dots (SIQDs) was studied. The luminescence spectrum of SlQDs was composed of three well-resolved transitions and each transition had a different saturation excitation intensity. The increase and saturation of luminescence was more clearly seen in the nonlinear luminescence, where the saturation excitation intensities for each energy level were demonstrated to be proportional to the degeneracies of each level. The nonlinear luminescence spectra were simulated by rate equations, taking account of the relaxation rate, the recombination rate. and the state-filling effect caused by Pauli blocking. As a result of fitting. the relaxation rate was estimated to be about 30 ps.
    研究論文(学術雑誌), 英語
  • Optical nonlinearity and response time in beryllium-doped standard temperature MBE grown GaAs/AlAs MQW
    T Okuno; Y Masumoto
    CLEO(R)/PACIFIC RIM 2001, VOL I, TECHNICAL DIGEST, IEEE, 掲載ページ 528-529, 出版日 2001年, 査読付, Dynamics of optical absorption saturation in Be-doped standard-temperature MBE gown GaAs/AlAs MQW was studied by using 200fs laser pulses. Response time becomes less than 1ps at doping [Be] > 1 x 10(19) cm(-3) which is in marked contrast to InGaAs/InAlAs MQW.
    研究論文(国際会議プロシーディングス), 英語
  • Large optical nonlinearity and fast response time in low-temperature grown GaAs/AlAs multiple quantum wells
    T Okuno; Y Masumoto; M Ito; H Okamoto
    APPLIED PHYSICS LETTERS, AMER INST PHYSICS, 77巻, 1号, 掲載ページ 58-60, 出版日 2000年07月, We have investigated optical nonlinearity in low-temperature (LT) molecular-beam-epitaxy-grown GaAs/AlAs multiple quantum wells (MQWs). Minimum saturation intensity, that is, maximum optical nonlinearity, is observed at around the excitonic absorption peak. The saturation intensity of the LT MQW is smaller by an order of magnitude than that of LT bulk GaAs. The response time of the LT MQW is 1/4-1/2 of the LT GaAs, and becomes less than 1 ps, corresponding to similar to 1/400 of the standard-temperature-grown MQW. These results demonstrate a clear advantage of the room-temperature excitons in the LT MQW having large optical nonlinearity as well as fast response time. (C) 2000 American Institute of Physics. [S0003-6951(00)03627-5].
    研究論文(学術雑誌), 英語
  • Size-dependent picosecond energy relaxation in PbSe quantum dots
    T Okuno; Y Masumoto; M Ikezawa; T Ogawa; AA Lipovskii
    APPLIED PHYSICS LETTERS, AMER INST PHYSICS, 77巻, 4号, 掲載ページ 504-506, 出版日 2000年07月, 査読付, We measured the size dependence of the energy relaxation time of PbSe quantum dots at room temperature. The radius of the dots was evaluated by small-angle x-ray scattering. We found a monotonic decrease of the relaxation time from 25 to 1 ps with a decrease of the radius r from 2.9 to 1.4 nm. The 1/r(3) dependence of the relaxation rate was indicated. (C) 2000 American Institute of Physics. [S0003- 6951(00)00230-8].
    研究論文(学術雑誌), 英語
  • Strong confinement of PbSe and PbS quantum dots
    T Okuno; AA Lipovskii; T Ogawa; Amagai, I; Y Masumoto
    JOURNAL OF LUMINESCENCE, ELSEVIER SCIENCE BV, 87-9巻, 掲載ページ 491-493, 出版日 2000年05月, We synthesized PbSe and PbS quantum dots in strong-confinement regime, and measured energy relaxation time by using pump-and-probe experiments. Energy relaxation time of PbSe dots in phosphate glasses showed clear correlation with the average radius. Smaller dots were shown to have shorter decay times. This dependence is ascribed to the relaxation to the surface of the dots. (C) 2000 Elsevier Science B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Imaging and single dot spectroscopy of InP self-assembled quantum dots
    M Sugisaki; HW Ren; SV Nair; JS Lee; S Sugou; T Okuno; Y Masumoto
    JOURNAL OF LUMINESCENCE, ELSEVIER SCIENCE BV, 87-9巻, 掲載ページ 40-45, 出版日 2000年05月, Optical properties of InP self-assembled quantum dots (SADs) embedded in Ga0.5In0.5P were studied under various conditions by means of the micro-spectroscopy. A strong optical anisotropy of the InP SADs was found in the macro-photoluminescence spectra and micro-photoluminescence (mu-PL) images showing two-fold symmetry, which reflects the anisotropic structure of the Ga0.5In0.5P matrix. Successive red-shifts of the mu-PL peaks and a recovery of the PL intensity with the increase of the temperature were clearly observed. The fluorescence intermittency from a single quantum dot was also investigated. The on-off switching rate is drastically enhanced by a weak near-IR laser beam irradiation. The influence of the matrix on the optical properties of the SADs is discussed. (C) 2000 Elsevier Science B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Confinement effects in strain-induced InGaAs/GaAs quantum dots
    HW Ren; SV Nair; JS Lee; S Sugou; T Okuno; K Nishbayashi; Y Masumoto
    PHYSICA E, ELSEVIER SCIENCE BV, 7巻, 3-4号, 掲載ページ 403-407, 出版日 2000年05月, The effects of both lateral and vertical confinements in strain-induced InGaAs/GaAs quantum dots were investigated by varying the InP stressor size, the width and composition of the quantum well as well as the GaAs caplayer thickness. The energy-level spacing decreases with increasing the stressor diameter and very large stressor leads to a barrel-shaped lateral confining potential rather than a parabolic one. The hydrostatic strain along the central axis of the stressor decays exponentially with a characteristic depth of about 25 nm. The quantum-dot state energies can be tuned easily by the quantum-well width and composition. If the QW is thin or the indium composition is small, the quantum dot states may be leaky due to weak vertical confinement. (C) 2000 Elsevier Science B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Systematic control of spectral hole burning and homogeneous linewidth by disorder in Y2O3 : Pr3+ crystalline systems
    T Okuno; T Suemoto
    PHYSICAL REVIEW B, AMER PHYSICAL SOC, 59巻, 14号, 掲載ページ 9078-9087, 出版日 1999年04月, We investigated the hole-burning phenomena and homogeneous Linewidth in Pr3+-doped Y2O3-based crystals under the systematic control of disorder in the crystal. When divalent ions are doped into an Y2O3:Pr3+ crystal, holes due to rearrangement of local structure around Pr3+ ions are burned. The burning curves are successfully analyzed in terms of a distributed tunneling rate model for hole formation. The burning efficiency from this analysis and the homogeneous linewidth. become larger as the crystal includes a larger amount of divalent ions. The interaction of Pr3+ ions with oxygen vacancies is thought to be one of the origins of the hole production and the Line broadening. The interaction length between Pr3+ ions and oxygen vacancies is discussed. [S0163-1829(99)01214-X].
    研究論文(学術雑誌), 英語
  • Excitonic luminescence from self-organized quantum dots of CdTe grown by molecular beam epitaxy
    S Kuroda; Y Terai; K Takita; T Okuno; Y Masumoto
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, JAPAN J APPLIED PHYSICS, 38巻, 4B号, 掲載ページ 2524-2528, 出版日 1999年04月, Self-organized quantum dots (QDs) of CdTe were successfully grown on a ZnTe (100) surface by molecular beam epitaxy. Atomic force microscopy measurements of the uncapped samples revealed the formation of CdTe QDs with typical dot diameters of 20 +/- 2 nm and heights of 2.7 +/- 0.3 nm when a 3.5 monolayer-thick CdTe was deposited. In the photoluminescence (PL) measurements of the capped QDs, an intensive excitonic luminescence was observed at 4.2 K, the intensity of which was higher than the CdTe/ZnTe single quantum wells (SQWs) by 2-4 orders of magnitude. The temperature dependence of the intensity showed thermal quenching with an activation energy of 110 meV, which was about twice as large as those of SQWs. The PL dt fay time in QDs exhibited a different temperature dependence from SQWs - a temperature-independent decay time below 20 K. These results are interpreted as features of zero-dimensional confinement of excitons in QDs.
    研究論文(学術雑誌), 英語
  • Temperature dependence of luminescence decay time of InP quantum disks
    T Okuno; HW Ren; M Sugisaki; K Nishi; S Sugou; Y Masumoto
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, JAPAN J APPLIED PHYSICS, 38巻, 2B号, 掲載ページ 1094-1097, 出版日 1999年02月, We measured temperature dependence of luminescence decay time of self-assembled InP dots in GaInP lattice-matched to GaAs. The radiative lifetime of InP-dot luminescence is independent of temperature below similar to 40 K and is linear with temperature between similar to 40 and similar to 120 K. These two features in the two temperature regimes are characteristic of zero-dimensional and two-dimensional structures, respectively. This temperature behavior of the lifetime is thought to be caused by the disklike shape of the InP dots; the dot lateral widths are longer than their heights, and thus they have an intermediate character between zero-dimension and two-dimensions.
    研究論文(学術雑誌), 英語
  • Optical anisotropy in self-assembled InP quantum dots
    M Sugisaki; HW Ren; SV Nair; K Nishi; S Sugou; T Okuno; Y Masumoto
    PHYSICAL REVIEW B, AMER PHYSICAL SOC, 59巻, 8号, 掲載ページ R5300-R5303, 出版日 1999年02月, Strong optical anisotropy is observed in the photoluminescence (PL) bands of both the InP self-assembled quantum dots and the Ga0.5In0.5P matrix. From the linearly polarized PL spectra measured under weak excitation, we found that large size quantum dots show strong anisotropy. The luminescence from a single quantum dot observed by the micro-FL technique revealed a doublet fine structure of the exciton levels that obey the linear polarization selection rule. The observed fine structure is shown to arise from an interplay of the electron-hole exchange interaction and the asymmetric crystal structure of the InP/Ga0.5In0.5P system.
    研究論文(学術雑誌), 英語
  • Zero-dimensional excitonic properties of self-organized quantum dots of CdTe grown by molecular beam epitaxy
    Y Terai; S Kuroda; K Takita; T Okuno; Y Masumoto
    APPLIED PHYSICS LETTERS, AMER INST PHYSICS, 73巻, 25号, 掲載ページ 3757-3759, 出版日 1998年12月, The successful growth of self-organized quantum dots (QDs) of CdTe on ZnTe (100) surface by molecular beam epitaxy is reported. Atomic force microscope measurements on the uncapped samples revealed the formation of CdTe QDs with typical dot diameters of 20+/-2 nm and heights of 2.7 +/- 0.3 nm at 3.5-ML-thick CdTe deposited. The intensity of photoluminescence (PL) from the capped QDs was higher than CdTe/ZnTe single quantum wells (SQWs) by a few orders of magnitude at 4.2 K, and exhibited a thermal quenching with an activation energy of 110 meV, which is about twice as large as those in SQWs. In time-resolved PL measurements, the decay time was almost independent of temperature below 20 K. This is interpreted as due to the zero-dimensional excitonic properties in QDs. (C) 1998 American Institute of Physics. [S0003-6951(98)03851-0].
    研究論文(学術雑誌), 英語
  • Magnetic field effects in InP self-assembled quantum dots
    M Sugisaki; HW Ren; K Nishi; S Sugou; T Okuno; Y Masumoto
    PHYSICA B-CONDENSED MATTER, ELSEVIER SCIENCE BV, 256巻, 掲載ページ 169-172, 出版日 1998年12月, Optical properties of InP self-assembled quantum dots (SADs) were investigated in the presence of a magnetic field up to 10 T. By using a mu m-sized InP/GaInP mesa, we succeeded in observing sharp photoluminescence (PL) lines from a single InP quantum dot. With the increase of the magnetic field, the diamagnetic shift and the Zeeman splitting were clearly observed in the Faraday configuration. The diamagnetic coefficient and the effective g-value of the confined excitons show fluctuations reflecting dispersion in the size and the shape of the quantum dots. The estimated g-value of the InP quantum dot is about half of that of the bulk InP because of the heavy-hole light-hole band mixing. (C) 1998 Elsevier Science B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Time-resolved luminescence study of InP quantum dots in GaInP matrix
    T Okuno; HW Ren; M Sugisaki; K Nishi; S Sugou; Y Masumoto
    SOLID-STATE ELECTRONICS, PERGAMON-ELSEVIER SCIENCE LTD, 42巻, 7-8号, 掲載ページ 1319-1323, 出版日 1998年07月, We performed time-resolved luminescence spectroscopy on self-assembled InP dots in GaInP lattice-matched to GaAs. The radiative lifetime of InP-dot luminescence is independent of temperature below 20 K, and is linear with temperature between 20 and 160 K. These two features in two temperature regimes are characteristic of zero-dimensional and two-dimensional structures, respectively. This temperature behavior of the lifetime is thought to be caused by the disk-like shape of the InP dots having an intermediate character between the zero-dimensional and the two-dimensional. Ar a low temperature of 2 K where the zero-dimensional feature is revealed, the carrier injection time from the GaInP matrix to the InP dots is estimated to be similar to 100 ps. This time is determined by carrier diffusion in the matrix. (C) 1998 Elsevier Science Ltd. All rights reserved.
    研究論文(学術雑誌), 英語
  • Self-organized quantum dots of zinc-blend MnTe grown by molecular beam epitaxy
    S Kuroda; Y Terai; K Takita; T Okuno; Y Masumoto
    JOURNAL OF CRYSTAL GROWTH, ELSEVIER SCIENCE BV, 184巻, 掲載ページ 274-278, 出版日 1998年02月, The successful growth by molecular beam epitaxy (MBE) of self-organized quantum dots (QDs) of zinc-blende (ZB) MnTe onto CdTe(100) is reported. Mn and Te fluxes were supplied either simultaneously (conventional MBE) or alternately (atomic layer epitaxy - ALE) onto the surface to form MnTe. Atomic-force microscope measurements for uncapped samples revealed that cone-shaped dots were formed in both of the two growth methods, however with different sizes. The diameter and the height are, respectively, given typically by D = 140 +/- 10 nm and h = 70 +/- 10 nm in QDs grown by conventional MBE, and by D = 60 +/- 5 nm and h = 8 +/- 1 nm in QDs grown by ALE, In photoluminescence (PL) and time-resolved PL measurements, a broad emission band due to the Mn2+ d-d transition was observed at 2.02 eV. Its decay time was found to be of the order of several tens to hundreds of nanoseconds, which is shorter than those from ZB-MnTe films by two or three orders. (C) 1998 Elsevier Science B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Temperature dependence of luminescence decay time of InP quantum disks
    T Okuno; HW Ren; M Sugisaki; K Nishi; S Sugou; Y Masumoto
    1998 INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE AND RELATED MATERIALS - CONFERENCE PROCEEDINGS, IEEE, 掲載ページ 147-150, 出版日 1998年, 査読付, We measured temperature dependence of luminescence decay time of self-assembled InP dots in GaInP lattice-matched to GaAs. The radiative lifetime of InP-dot luminescence is independent of temperature below similar to 40 K, and is linear with temperature between similar to 40 and similar to 120 K. These two features in the two temperature regimes are characteristic of zero-dimensional and two-dimensional structures, respectively. This temperature behavior of the lifetime is thought to be caused by disk-like shape of the InP dots; they have longer lateral widths than their heights, and thus have the intermediate character between the zero-dimension and the two-dimension.
    研究論文(国際会議プロシーディングス), 英語
  • Fine splitting in the optical spectra of InP self-assembled single quantum dot
    M Sugisaki; HW Ren; SV Nair; K Nishi; S Sugou; T Okuno; Y Masumoto
    PROCEEDINGS OF THE THIRD INTERNATIONAL CONFERENCE ON EXCITONIC PROCESSES IN CONDENSED MATTER - EXCON '98, ELECTROCHEMICAL SOCIETY INC, 98巻, 25号, 掲載ページ 298-303, 出版日 1998年, 査読付, Strong optical anisotropy of the photoluminescence (PL) spectra in InP self-assembled quantum dots is observed in the luminescence bands of both the quantum dots and the Ga0.5In0.5P matrix. By comparing the linear polarized PZ spectra, we found that large size quantum dots show strong anisotropy. The luminescence from a single quantum dot observed by the micro-FL technique revealed a, doublet line structure of the exciton levels which obey linear polarization selection rule. The observed fine structure is shown to arise from an interplay of the electron-hole exchange interaction and the asymmetric crystal structure of the InP/GaInP system.
    研究論文(国際会議プロシーディングス), 英語
  • Time-resolved luminescence of InP quantum dots in a Ga0.5In0.5P matrix: Carrier injection from the matrix
    T Okuno; HW Ren; M Sugisaki; K Nishi; S Sugou; Y Masumoto
    PHYSICAL REVIEW B, AMER PHYSICAL SOC, 57巻, 3号, 掲載ページ 1386-1389, 出版日 1998年01月, 査読付, We conducted time-resolved luminescence spectroscopy on self-assembled InP dots in a Ga0.5In0.5P matrix at different photon excitation energies. In comparison with results on Ga0.5In0.5P without dots, the influence of the Ga0.5In0.5P matrix on luminescence-decay profiles of InP dots was clarified, By excitation at the Ga0.5In0.5P matrix, the long-decay component (similar to 50 ns), as well as the 400 ps radiative-decay component, was observed in luminescence of InP dots. This long-decay component reflects carrier lifetime in the Ga0.5In0.5P matrix, Carrier injection time from the Ga0.5In0.5P matrix to InP dots is estimated to be similar to 100 ps, and is determined by carrier diffusion in the matrix.
    研究論文(学術雑誌), 英語
  • Defect-induced persistent hole burning in MgO-doped Pr3+: YAG systems
    T Suemoto; T Okuno; D Nakano
    OPTICS COMMUNICATIONS, ELSEVIER SCIENCE BV, 145巻, 1-6号, 掲載ページ 113-118, 出版日 1998年01月, Persistent spectral holes have been found in Pr3+:YAG, when a small amount of MgO was co-doped. The holes are stable against temperature cycling up to 100 K. The initial hole burning rate shows a roughly linear dependence on the concentration of Mg2+ ions in the matrix. This suggests that the persistent hole is induced by the defects associated with the co-doping of the Mg2+ ions. (C) 1998 Elsevier Science B.V.
    研究論文(学術雑誌), 英語
  • Reconsideration of relaxation processes of excitons in CuCl nanocrystals
    T Okuno; A Satake; Y Masumoto
    JOURNAL OF LUMINESCENCE, ELSEVIER SCIENCE BV, 72-4巻, 掲載ページ 383-385, 出版日 1997年06月, 査読付, We report temporal changes of luminescence and induced absorption of excitons in nanometer-size semiconductor crystals (nanocrystals) of CuCl embedded in NaCl or in glass, and discuss relaxation mechanisms of the excitons. In CuCl nanocrystals in NaCl, luminescence-decay or -rise is observed at ''free''- or ''localized''-state luminescence, respectively. This indicates nonradiative relaxation from the ''free'' exciton to the ''localized'' state. In CuCl nanocrystals in glass, the temporal changes of the induced absorption have a longer decay component, in addition to a fast decay component which agrees with the luminescence decay. This result suggests exciton decomposition and existence of an electron remainder in the nanocrystals.
    研究論文(学術雑誌), 英語
  • Exciton localization and decomposition dynamics in cuprous halide nanocrystals
    T Okuno; H Miyajima; A Satake; Y Masumoto
    PHYSICAL REVIEW B, AMERICAN PHYSICAL SOC, 54巻, 23号, 掲載ページ 16952-16957, 出版日 1996年12月, 査読付, We report temporal changes of luminescence and absorption (differential transmission) of excitons in nanometer-size semiconductor crystals (nanocrystals) of CuCl embedded in NaCl or in glass, and CuBr nanocrystals embedded in glas. In CuCl nanocrystals in NaCl, an exciton relaxes nonradiatively to some localized state. In CuCl and CuBr nanocrystals in glass, the temporal changes of the differential transmission have a longer decay component in addition to the fast decay component which agrees with the luminescence decay. This result suggests exciton decomposition and the existence of an electron or a hole remainder in the nanocrystals. The decay time of the longer decay component increases by the accumulation of photoexcitation. This phenomenon indicates persistent trapping of carriers in the glass matrix, which is concerned with persistent spectral hole burning in nanocrystals.
    研究論文(学術雑誌), 英語
  • Observation of two types of spectral holes in MgO-doped Y2O3:Pr3+ crystals
    T Okuno; K Tanaka; T Suemoto
    OPTICS COMMUNICATIONS, ELSEVIER SCIENCE BV, 123巻, 4-6号, 掲載ページ 512-516, 出版日 1996年02月, 査読付, In addition to a narrow spectral hole due to optical pumping to hyperfine sublevels in the ground state, an anomalously broad persistent spectral hole was burned in Y2O3:Pr3+ crystals which contain a small amount of MgO. This broad hole was stable against 300 K-annealing. Burning of this broad hole is ascribed to the rearrangement of local structure around optical centers.
    研究論文(学術雑誌), 英語
  • Two types of spectral holes in Y2O3:Pr3+ crystalline systems
    Tsuyoshi Okuno; Tohru Suemoto
    Journal of Luminescence, Elsevier Science B.V., 66-67巻, 1-6号, 掲載ページ 179-183, 出版日 1995年, 査読付, In Y2O3:Pr3+, we found a crossover of the hole-burning mechanism between particular temperature ranges
    narrow holes due to the optical pumping were burned at low temperature (4.2 K), while broader holes with higher thermal stability (stable hole) were burned at higher temperature (11-20 K). We can understand this temperature behavior by using a simple 3-level model for the optical pumping process. On the contrary, in Y2O3-MO (M2+ = Mg2+, Ca2+, or Ba2+):Pr3+ systems, the stable broad hole was burned at all temperatures below 40 K.
    研究論文(学術雑誌), 英語
  • LUMINESCENCE SIDE BANDS DUE TO DISTRIBUTED STARK LEVELS IN PR3+-ZRO2-Y2O3(YSZ)
    T OKUNO; K TANAKA; K KOYAMA; T SUEMOTO
    JOURNAL OF LUMINESCENCE, ELSEVIER SCIENCE BV, 60-1巻, 掲載ページ 85-88, 出版日 1994年04月, 査読付, In Pr3+:ZrO2-Y2O3, luminescence side bands are observed around resonant fluorescence under excitation at 6142 angstrom. The behavior of the side bands with changing temperature is successfully explained by assuming that the lower state of the transition splits into three Stark levels which are in thermal equilibrium.
    研究論文(学術雑誌), 英語
  • The role of divalent ions in persistent hole-burning mechanism in Y2O3 : Pr3+ crystals(jointly worked)
    1994 OSA Technical Digest Series, 15巻, 掲載ページ 242-245, 出版日 1994年
    英語
  • HOMOGENEOUS LINE-WIDTH OF PRASEODYMIUM IONS IN VARIOUS INORGANIC MATERIALS
    T OKUNO; K TANAKA; K KOYAMA; M NAMIKI; T SUEMOTO
    JOURNAL OF LUMINESCENCE, ELSEVIER SCIENCE BV, 58巻, 1-6号, 掲載ページ 184-187, 出版日 1994年01月, 査読付, Persistent spectral hole burning and fluorescence line narrowing spectroscopy was applied to Pr3+ doped silicate glass, yttria stabilized zirconia, and yttria, to investigate homogeneous line width (GAMMA). In the temperature (T) dependence of GAMMA, T-linear components are commonly found below 10 K in these three materials, and their magnitudes are found to become larger as the degree of disorder increases.
    研究論文(学術雑誌), 英語
  • PERSISTENT SPECTRAL HOLE-BURNING OF PR-3+ IONS IN YTTRIA STABILIZED ZIRCONIA - A NEW HOLE-BURNING MATERIAL
    K TANAKA; T OKUNO; H YUGAMI; M ISHIGAME; T SUEMOTO
    OPTICS COMMUNICATIONS, ELSEVIER SCIENCE BV, 86巻, 1号, 掲載ページ 45-50, 出版日 1991年10月, 査読付, Persistent spectral hole-burning has been observed in Pr3+ doped yttria stabilized zirconia (YSZ) and used to measure the homogeneous linewidth (GAMMA-h). Holes can be burned only in the lowest crystal field component of the H-3(4) --> 1D2 transition of Pr3+ ions (6115 angstrom, inhomogeneous linewidth: approximately 100 cm-1) and observed below 25 K. Homogeneous linewidth of the transition is found to be 155 MHz at 4.2 K and to have a T1.20 +/- 0-1-dependence. Such a temperature dependence is quite similar to that usually observed in organic-molecules-doped polymers and coupling of electrons to the two level system (TLS) is suggested for the phase relaxation process.
    研究論文(学術雑誌), 英語

MISC

  • 巻頭言 四半世紀をむかえる「大学の物理教育」誌
    奥野剛史
    一般社団法人 日本物理学会, 出版日 2019年03月, 日本物理学会誌 BUTSURI, 74巻, 3号, 掲載ページ 125, 日本語, 査読付, 招待, その他, 0029-0181
  • Eu2+含有シリコン硫化物からの黄色発光 = シリコンウェーハ上に形成されるEu2+蛍光体物質 =
    奥野剛史
    日本工業出版, 出版日 2009年01月, 光アライアンス, 20巻, 1号, 掲載ページ 29-32, 日本語, 記事・総説・解説・論説等(その他), 0917-026X, 40016404640, AA11758790
  • Absorption saturation intensity of InGaAs-InAlAs MQW under tensile and compressive strain
    T Okuno; Y Masumoto; A Higuchi; H Yoshino; H Bando; H Okamoto
    Optical absorption saturation intensity Is was measured by using femtosecond light pulse for InxGa1-xAs-In(0.52)Al(0.48)AS MQW grown on InP (100) substrates. Is showed minimum at x=0.46 (under tensile strain). This was in marked contrast to the previous results., IEEE, 出版日 2004年, 2004 International Conference on Indium Phosphide and Related Materials, Conference Proceedings, 掲載ページ 560-561, 英語, 1092-8669, WOS:000228291000147

講演・口頭発表等

  • beta-SiAlONに添加したEu2+ による発光の減衰曲線解析
    須田順子; 奥野剛史; 武田隆史; 高橋向星; 広崎尚登
    口頭発表(一般), 日本語, (2024.3)71回応用物理学会春季学術講演会 講演予稿集24a-12J-8
    発表日 2024年03月24日
  • アップコンバージョン蛍光体Y4(SiS4)3:Er3+ の発光特性
    山中遥翔; 奥野剛史
    ポスター発表, 日本語, (2024.3)71回応用物理学会春季学術講演会 講演予稿集23p-P04-18
    発表日 2024年03月23日
  • 金属における発光寿命と強度の系統的な理解に向けて
    末元徹; 森野春樹; 奥野剛史; 小野頌太; 鈴木剛; 岡崎浩三; 谷峻太郎; 小林洋平
    口頭発表(一般), 日本語, (2024.3)第71回応用物理学会春季学術講演会 講演予稿集23a-13N-5
    発表日 2024年03月23日
  • CaS:Yb2+ における熱蛍光および近赤外光励起赤色発光
    西川優大; 奥野剛史
    (2023.9)第84回応用物理学会秋季学術講演会 講演予稿集23p-A305-7
    発表日 2023年09月23日
  • 銅ニッケル合金の近赤外領域における超高速発光の組成比依存性
    森野春樹; 末元徹; 奥野剛史; 小野頌太; 鈴木剛; 岡崎浩三; 小林洋平; 谷峻太郎
    (2023.9) 日本物理学会第78回年次大会 講演概要集16a-B104-2
    発表日 2023年09月16日
  • 金属におけるフェムト秒赤外発光の特性と状態密度の相関
    末元徹; 小野頌太; 森野春樹; 奥野剛史; 鈴木剛; 岡崎浩三; 小林洋平; 谷峻太郎
    (2023.9) 日本物理学会第78回年次大会 講演概要集16a-B104-1
    発表日 2023年09月16日
  • CaS:Yb2+ における近赤外光励起による赤色光刺激発光
    西川優大; 奥野剛史; 井口一秋
    ポスター発表, 日本語, (2023.3)第70回応用物理学会春季学術講演会 上智大学 講演予稿集16a-PB06-2
    発表日 2023年03月16日
    開催期間 2023年03月16日
  • 金属における超高速発光特性と電子比熱の相関
    末元徹; 森野春樹; 奥野剛史; 小野頌太; 鈴木剛; 岡崎浩三; 谷峻太郎; 小林洋平
    ポスター発表, 日本語, (2023.3)第70回応用物理学会春季学術講演会 上智大学 講演予稿集16a-PA04-5
    発表日 2023年03月16日
    開催期間 2023年03月16日
  • 銅ニッケル合金における近赤外超高速発光の組成依存
    森野春樹; 末元徹; 奥野剛史; 小野頌太; 鈴木剛; 岡崎浩三; 谷峻太郎; 小林洋平
    ポスター発表, 日本語, (2023.3)第70回応用物理学会春季学術講演会 上智大学 講演予稿集16a-PA04-6
    発表日 2023年03月16日
    開催期間 2023年03月16日
  • ミリ秒残光を示すEu2+ 添加蛍光体の残光特性
    須田順子; 奥野剛史
    ポスター発表, 日本語, (2023.3)第70回応用物理学会春季学術講演会 上智大学 講演予稿集16a-PB06-2
    発表日 2023年03月16日
    開催期間 2023年03月
  • CaS:Eu2+,Mn2+ 赤色残光蛍光体の発光特性
    井口一秋、奥野剛史、田村祐樹、山口翔太
    ポスター発表, 日本語, (2022.3)応用物理学会 青山学院大学相模原キャンパス(神奈川県)オンラインハイブリッド開催第69回春季学術講演会予稿集23a-P02-4, 応用物理学会(2022.3), 青山学院大学相模原キャンパス(神奈川県)・オンラインハイブリッド開催
    発表日 2022年03月
    開催期間 2022年03月23日
  • Cs2Cu2I5 の発光に関する研究
    西原睦喜、奥野剛史
    ポスター発表, 日本語, (2022.3)応用物理学会 青山学院大学相模原キャンパス(神奈川県)オンラインハイブリッド開催第69回春季学術講演会予稿集23a-P02-3, 応用物理学会(2022.3), 青山学院大学相模原キャンパス(神奈川県)・オンラインハイブリッド開催
    発表日 2022年03月
    開催期間 2022年03月23日
  • CaS:Eu2+,Tm3+ の欠陥による発光の特徴と赤色残光
    須田順子、田村祐樹、山口翔太、七井靖、奥野剛史
    口頭発表(一般), 日本語, (2022.3)応用物理学会 青山学院大学相模原キャンパス(神奈川県)オンラインハイブリッド開催第69回春季学術講演会予稿集22a-D316-6, 応用物理学会(2022.3), 青山学院大学相模原キャンパス(神奈川県)・オンラインハイブリッド開催
    発表日 2022年03月
    開催期間 2022年03月22日
  • CaAl2O4:Ce3+,Dy3+の白色発光および残光特性
    磯部英智香、渡部勇太、奥野剛史、木村浩丈、山口翔太
    ポスター発表, 日本語, 応用物理学会(2021春) オンライン開催 2021年第68回応用物理学会春季学術講演会, 応用物理学会(2021.3), オンライン開催
    開催期間 2021年03月19日
  • 赤色残光蛍光体CaS:Eu2+,Dy3+のアルカリ金属イオン添加効果
    山口翔太、奥野剛史、田村祐樹、須田順子
    ポスター発表, 日本語, 応用物理学会(2021春) オンライン開催 2021年第68回応用物理学会春季学術講演会, 応用物理学会(2021.3), オンライン開催
    開催期間 2021年03月19日
  • 3価のサマリウム原料を用いた蛍光体SrFCl:Sm2+の作製
    木村浩丈、奥野剛史、黒川郁弥、富田一光
    ポスター発表, 日本語, 応用物理学会(2021春) オンライン開催 2021年第68回応用物理学会春季学術講演会, 応用物理学会(2021.3), オンライン開催
    開催期間 2021年03月19日
  • 青色励起赤色発光リン酸塩蛍光体の発光特性
    志村佳熙、久島大輝、田村祐樹、奥野剛史
    口頭発表(一般), 日本語, 映像情報メディア学会 発光型/非発光型ディスプレイ合同研究会 オンライン 2021年1月28日-29日 (発表は29日) ITE Technical Report vol45,no2 IDY2021-1(Jan.2020) pp.33-36, 映像情報メディア学会, オンライン
    開催期間 2021年01月29日
  • VBAとGASを用いたシフト表自動化アプリの作成とシフト組合せ最適化用の遺伝的アルゴリズムの検討
    富田一光、奥野剛史
    口頭発表(一般), 日本語, 進化計算学会 第14回進化計算シンポジウム2020 講演論文集p101-106 2020年12月19日-20日(発表は20日)オンライン開催 Z3-02, 進化計算学会, オンライン
    開催期間 2020年12月20日
  • 可視光励起可能な赤色残光蛍光体CaS:Eu2+,Tm3+の発光特性
    田村祐樹、奥野剛史、須田順子、七井靖
    ポスター発表, 日本語, 応用物理学会(2020春) 上智大学四谷キャンパス、千代田区(東京都)2020年第67回応用物理学会春季学術講演会, 応用物理学会(2020.3), 上智大学 四谷キャンパス、千代田区(東京都)
    開催期間 2020年03月13日
  • 青色励起赤色発光リン酸塩蛍光体の発光および残光特性
    志村佳熙、奥野剛史、久島大輝
    ポスター発表, 日本語, 応用物理学会(2020春) 上智大学四谷キャンパス、千代田区(東京都)2020年第67回応用物理学会春季学術講演会, 応用物理学会(2020.3), 上智大学 四谷キャンパス、千代田区(東京都)
    開催期間 2020年03月13日
  • 希土類フリー蛍光体Zn3(PO4)2:Mn2+,Si4+とZn3(PO4)2:Mn2+,Ga3+の評価
    富田 一光、奥野 剛史
    ポスター発表, 日本語, 応用物理学会(2020春) 上智大学四谷キャンパス、千代田区(東京都)2020年第67回応用物理学会春季学術講演会, 応用物理学会(2020.3), 上智大学 四谷キャンパス、千代田区(東京都)
    開催期間 2020年03月13日
  • シリコン上に膜形成可能なシリコン硫化物蛍光体の研究
    中村裕貴、青野瑞樹、奥野剛史、七井靖
    口頭発表(一般), 日本語, 映像情報メディア学会 発光型/非発光型ディスプレイ合同研究会 鳥取大学 鳥取キャンパス 鳥取市(鳥取県) 2020年1月23日-24日 (発表は23日) ITE Technical Report vol44,no1 IDY2020-10(Jan.2020) pp.33-36, 映像情報メディア学会, 鳥取大学 鳥取キャンパス 鳥取市(鳥取県)
    開催期間 2020年01月23日
  • 新規固体光源のための光材料研究ー半導体、ナノ材料、蛍光体ー
    奥野剛史
    口頭発表(招待・特別), 日本語, 2019年度(第52回)照明学会全国大会, 招待, 照明学会, 九州大学伊都キャンパス, 光源・照明システム分科会が主催するシンポジウム。テーマは「光源・照明システムの未来」。4個の分科会が合併して光源・照明システム分科会が今回発足したのにあたって開かれたシンポジウム。旧固体光源分科会から、発表者の研究内容および旧分科会で行われていたいくつかの研究例を紹介した。, 国内会議
    発表日 2019年09月11日
  • Zn3(PO4)2:Mn2+,Ga3+ の熱蛍光特性と燐光減衰曲線の評価
    富田 一光、奥野 剛史
    口頭発表(一般), 日本語, 応用物理学会(2019春) 東京工業大学大岡山キャンパス、目黒区(東京都)2019年第66回応用物理学会春季学術講演会, 応用物理学会(2019.3), 東京工業大学大岡山キャンパス、目黒区(東京都)
    開催期間 2019年03月12日
  • CaAl2O4:M,Ga3+ (M=Ce3+,Eu2+) 蛍光体の発光特性
    渡部 勇太、奥野 剛史
    口頭発表(一般), 日本語, 応用物理学会(2019春) 東京工業大学大岡山キャンパス、目黒区(東京都)2019年第66回応用物理学会春季学術講演会, 応用物理学会(2019.3), 東京工業大学大岡山キャンパス、目黒区(東京都)
    開催期間 2019年03月12日
  • ボールミルを用いたBaMoO4:Eu3+ の作製
    柿野 良太郎、奥野 剛史
    口頭発表(一般), 日本語, 応用物理学会(2019春) 東京工業大学大岡山キャンパス、目黒区(東京都)2019年第66回応用物理学会春季学術講演会, 応用物理学会(2019.3), 東京工業大学大岡山キャンパス、目黒区(東京都)
    開催期間 2019年03月12日
  • 青色励起可能な赤色発光リン酸塩蛍光体の発光特性
    久島 大輝、奥野 剛史
    口頭発表(一般), 日本語, 応用物理学会(2019春) 東京工業大学大岡山キャンパス、目黒区(東京都)2019年第66回応用物理学会春季学術講演会, 応用物理学会(2019.3), 東京工業大学大岡山キャンパス、目黒区(東京都)
    開催期間 2019年03月12日
  • II-Y2S4蛍光体の発光波長制御
    黒川 郁弥、奥野 剛史
    口頭発表(一般), 日本語, 応用物理学会(2019春) 東京工業大学大岡山キャンパス、目黒区(東京都)2019年第66回応用物理学会春季学術講演会, 応用物理学会(2019.3), 東京工業大学大岡山キャンパス、目黒区(東京都)
    開催期間 2019年03月12日
  • 亜鉛を含むシリコン硫化物蛍光体膜の作製と評価
    中村 裕貴、奥野 剛史
    口頭発表(一般), 日本語, 応用物理学会(2019春) 東京工業大学大岡山キャンパス、目黒区(東京都)2019年第66回応用物理学会春季学術講演会, 応用物理学会(2019.3), 東京工業大学大岡山キャンパス、目黒区(東京都)
    開催期間 2019年03月12日
  • 低速電子線励起用新規橙赤色硫化物蛍光体の開発
    奥野剛史、中川康弘、志村佳熙、七井靖、佐藤義孝、御園生敏行
    口頭発表(一般), 日本語, 電子情報通信学会 発光型/非発光型ディスプレイ合同研究会 鹿児島大学 群元キャンパス 鹿児島市(鹿児島県) 2019年1月24日-25日 (発表は25日) EID24 信学技報 IEICE Technical Report EID2018-12(2019-1) pp.89-92, 電子情報通信学会, 鹿児島大学 群元キャンパス 鹿児島市(鹿児島県)
    開催期間 2019年01月25日
  • 赤色蛍光体CaAlSiN3:Eu2+の低Eu2+濃度における青色発光の検討
    須田 順子、神垣 良昭、奥野 剛史
    口頭発表(一般), 日本語, 応用物理学会(2018春) 早稲田大学西早稲田キャンパス・ベルサール高田馬場、新宿区(東京都)2018年 2018年第65回応用物理学会春季学術講演会, 応用物理学会(2018.3), 早稲田大学西早稲田キャンパス・ベルサール高田馬場、新宿区(東京都)
    開催期間 2018年03月19日
  • La2S3:Ce3+の赤色カソードルミネッセンスおよびフォトルミネッセンス
    中川 康弘、奥野 剛史、七井 靖
    口頭発表(一般), 日本語, 応用物理学会(2018春) 早稲田大学西早稲田キャンパス・ベルサール高田馬場、新宿区(東京都)2018年 2018年第65回応用物理学会春季学術講演会, 応用物理学会(2018.3), 早稲田大学西早稲田キャンパス・ベルサール高田馬場、新宿区(東京都)
    開催期間 2018年03月19日
  • 発光色の調整可能なCaM2O4:Eu3+ (M = Sc,In)蛍光体の発光特性
    佐々木 智徳、奥野 剛史、極檀 紘希
    口頭発表(一般), 日本語, 応用物理学会(2018春) 早稲田大学西早稲田キャンパス・ベルサール高田馬場、新宿区(東京都)2018年 2018年第65回応用物理学会春季学術講演会, 応用物理学会(2018.3), 早稲田大学西早稲田キャンパス・ベルサール高田馬場、新宿区(東京都)
    開催期間 2018年03月19日
  • Ca2SiS4:Eu2+,Er3+蛍光体の残光特性
    保木 渉馬、奥野 剛史、青野 瑞樹、七井 靖
    口頭発表(一般), 日本語, 応用物理学会(2018春) 早稲田大学西早稲田キャンパス・ベルサール高田馬場、新宿区(東京都)2018年 2018年第65回応用物理学会春季学術講演会, 応用物理学会(2018.3), 早稲田大学西早稲田キャンパス・ベルサール高田馬場、新宿区(東京都)
    開催期間 2018年03月17日
  • Broad luminescence of Ce3+ in multiple sites in (La,Ce,Y)6Si4S17 phosphor
    Yasushi Nanai, Hayato Kamioka and Tsuyoshi Okuno
    ポスター発表, 英語, International Symposium on Novel Energy Nanomaterials, Catalysts and Surfaces for Future Earth, The University of Electro-Communications, Tokyo, Japan
    開催期間 2017年10月28日
  • 青色蛍光体SrAl2O4:Ce3+ におけるGa添加による発光向上
    極檀紘希、奥野剛史、七井靖
    口頭発表(一般), 日本語, 応用物理学会(2017春) パシフィコ横浜、横浜市(神奈川)2017年 2017年第64回応用物理学会春季学術講演会, 応用物理学会(2017.3), パシフィコ横浜、横浜市(神奈川)
    開催期間 2017年03月16日
  • Y4(SiS4)3:Ln3+ 蛍光体の温度特性およびエネルギー緩和過程
    満澤隆太郎、鈴木洋介、奥野剛史、七井靖
    口頭発表(一般), 日本語, 応用物理学会(2017春) パシフィコ横浜、横浜市(神奈川)2017年 2017年第64回応用物理学会春季学術講演会, 応用物理学会(2017.3), パシフィコ横浜、横浜市(神奈川)
    開催期間 2017年03月16日
  • Sr2SiS4:Eu2+,Ln3+ 蛍光体の発光および残光特性
    青野瑞樹、奥野剛史、七井靖
    口頭発表(一般), 日本語, 応用物理学会(2017春) パシフィコ横浜、横浜市(神奈川)2017年 2017年第64回応用物理学会春季学術講演会, 応用物理学会(2017.3), パシフィコ横浜、横浜市(神奈川)
    開催期間 2017年03月16日
  • 2価、4価イオン共添加Y2O2S:Eu3+ 蛍光体の熱蛍光特性
    滝沢健太、奥野剛史、七井靖
    口頭発表(一般), 日本語, 応用物理学会(2017春) パシフィコ横浜、横浜市(神奈川)2017年 2017年第64回応用物理学会春季学術講演会, 応用物理学会(2017.3), パシフィコ横浜、横浜市(神奈川)
    開催期間 2017年03月16日
  • 逆オパール構造とナノ粒子構造を有する増感太陽電池用TiO2 電極の光吸収・発光・光電子収量特性評価
    豊田太郎、奥野剛史、神山慶太、早瀬修二、沈青
    口頭発表(一般), 日本語, 応用物理学会(2017春) パシフィコ横浜、横浜市(神奈川)2017年 2017年第64回応用物理学会春季学術講演会, 応用物理学会(2017.3), パシフィコ横浜、横浜市(神奈川)
    開催期間 2017年03月14日
  • (La,Ce,Y)6Si4S17 蛍光体の時間分解発光特性
    七井靖,上岡隼人,奥野剛史
    口頭発表(一般), 日本語, 応用物理学会(2016秋) 新潟朱鷺メッセ、新潟市 2016年 2016年第77回応用物理学会秋季学術講演会, 応用物理学会(2016.9), 新潟朱鷺メッセ、新潟市
    開催期間 2016年09月15日
  • 新規シリコン硫化物蛍光体の母体励起発光
    七井靖、奥野剛史
    口頭発表(招待・特別), 日本語, 第363回蛍光体同学会, 蛍光体同学会, 講演予稿集p7-14, 国内会議
    開催期間 2016年06月03日
  • (La,Ce,Y)6Si4S17 蛍光体の発光帯とCe3+ 置換サイトとの関係
    七井靖,花輪有紀,上岡隼人,奥野剛史
    口頭発表(一般), 日本語, 応用物理学会(2016春) 東京工業大学、目黒区(東京)2016年 2016年第63回応用物理学会春季学術講演会, 応用物理学会(2016.3), 東京工業大学、目黒区(東京)
    開催期間 2016年03月21日
  • Y4(SiS4)3:Ce3+ 蛍光体の粒径および均一性の評価
    片柳賢祐,奥野剛史,七井靖,御園生敏行,佐藤義孝
    ポスター発表, 日本語, 応用物理学会(2016春) 東京工業大学、目黒区(東京)2016年 2016年第63回応用物理学会春季学術講演会, 応用物理学会(2016.3), 東京工業大学、目黒区(東京)
    開催期間 2016年03月20日
  • 黄色から赤色の残光蛍光体 Ca2SiS4:Eu におけるNd3+, Gd3+ 添加の影響
    清水裕介,奥野剛史,七井靖
    ポスター発表, 日本語, 応用物理学会(2016春) 東京工業大学、目黒区(東京)2016年 2016年第63回応用物理学会春季学術講演会, 応用物理学会(2016.3)
    開催期間 2016年03月20日
  • イットリウムチオシリケート蛍光体の温度特性に関する研究
    満澤隆太郎、鈴木洋介、奥野剛史、七井靖
    口頭発表(一般), 日本語, 応用物理学会(2016春) 東京工業大学、目黒区(東京)2016年 2016年第63回応用物理学会春季学術講演会, 応用物理学会(2016.3), 東京工業大学、目黒区(東京)
    開催期間 2016年03月20日
  • 添加物による Y4(SiS4)3 蛍光体の発光特性の研究
    鈴木智大,奥野剛史,七井靖
    ポスター発表, 日本語, 応用物理学会(2016春) 東京工業大学、目黒区(東京)2016年 2016年第63回応用物理学会春季学術講演会, 応用物理学会(2016.3), 東京工業大学、目黒区(東京)
    開催期間 2016年03月20日
  • 新規シリコン硫化物蛍光体の探索
    七井靖、奥野剛史
    口頭発表(招待・特別), 日本語, 第358回蛍光体同学会, 蛍光体同学会, 講演予稿集p9-15, 国内会議
    開催期間 2015年06月05日

所属学協会

  • 2017年03月 - 現在
    照明学会
  • 2012年05月 - 現在
    蛍光体同学会
  • 2010年10月 - 現在
    日本物理教育学会
  • 1997年01月 - 現在
    応用物理学会
  • 1991年01月 - 現在
    日本物理学会

共同研究・競争的資金等の研究課題

  • 可視光から近赤外光の波長可変励起による微弱光検出を利用した蓄光蛍光体の研究
    奥野剛史
    日本学術振興会, 科学研究費助成事業, 電気通信大学, 基盤研究(C), 研究代表者, 本研究は、蓄光蛍光体に光をあてた際に、そのエネルギーを蓄えている実体とエネルギーの深さを、さまざまな色の光をあてて、生じる微弱な蓄光の強さを検出することによって明らかにしようとするものである。, 22K04682
    研究期間 2022年04月 - 2025年03月
  • 母体の光吸収波長を利用した低温焼成新規高演色蛍光体材料の開拓
    奥野剛史
    研究代表者, 本研究の目的は、母体の光吸収波長を最大限に利用することのできる新規高演色蛍光体材料を開拓することである。吸収波長領域の幅は350nmから450nmの間に20nm以上、室温での内部量子効率が60%以上、発光波長は630nm以上670nm以下のものを得る。これを実現するために、母体で光励起された電子および正孔が、蛍光イオンへ捕獲されてエネルギー移動が良好に生じるための機構を解明する。エネルギー移動の効率が高まるために母体がもつべき不純物準位の条件を明らかにする。 本研究では、650Cから1050C程度の低温かつ硫黄蒸気下で作製可能な硫化物、および、そこから派生する物質群や作製方法を利用する。エネルギー移動を促進する新しい不純物準位や、さまざまな蛍光イオンの導入を試みる。母体の光励起波長、赤色の発光波長、母体に含まれる不純物準位、これらを制御して新規蛍光体を開拓する。
    研究期間 2016年04月01日 - 2019年03月31日

産業財産権

  • 蛍光体、その製造方法及び発光装置
    特許権, 七井靖, 奥野剛史, 特願2012-272083, 出願日: 2012年12月13日, 国立大学法人電気通信大学, 特開2014-118421, 公開日: 2014年06月30日, 6099126, 発行日: 2017年03月03日
  • 発光素子とその製造方法、並びにErSi2ナノワイヤーとその製造方法
    特許権, 大田直樹, 奥野剛史, 特願2007-142044, 出願日: 2007年05月29日
  • 半導体素子
    特許権, 岡本紘, 坂東弘之, 高橋了, 吉野英生, 舛本泰章, 奥野剛史, 特願2004-249408, 出願日: 2004年08月30日, 国立大学法人千葉大学、国立大学法人筑波大学、国立大学法人電気通信大学, 特許公開2006-065133