Hasanudin

Publications (16)5.69 Total impact

• Article: Infrared study on pressure-induced charge delocalization in Cs2TCNQ3

  Hasanudin, N Kuroda, T Kagayama, T Sugimoto
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  ABSTRACT: Pressure dependence of several molecular vibration modes in Cs2TCNQ3 has been observed through infrared absorption measurements. The behaviour of the C–CN and C–H stretching modes suggests that a phase transition takes place at around 3.6 GPa. The π*-electrons, which are localized on TCNQ− molecules in the low-pressure phase, are delocalized significantly in the high-pressure phase. However, the radical-like and neutral-like molecules still coexist in the high-pressure phase indicating that the electrons are not completely delocalized. The electron–molecular-vibration coupled mode disappears in the high-pressure phase in coincidence with the disappearance of the inter-radical charge-transfer band S1, proving the strong coupling between them.
  Journal of Physics Condensed Matter 10/2002; 14(44):10419. · 2.55 Impact Factor
• Article: High Pressure Optical Absorption in Cs 2 TCNQ 3 Complexes Grown Under the Influence of Magnetic Field

  Hasanudin, N. Kuroda, T. Kagayama, T. Sugimoto, I. Mogi, K. Watanabe, M. Motokawa
  International Journal of High Pressure Research. 01/2002; 22(2):251-255.
• Article: High Pressure Optical Absorption in Organic Semiconductors (NMe4)2TCNQ3 and Cs2TCNQ3

  Hasanudin, T. Kagayama, N. Kuroda, T. Sugimoto
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  ABSTRACT: The pressure dependence of the optical absorption spectra of (NMe4)2TCNQ3 and Cs2TCNQ3 has been measured at room temperature in the spectral range from mid-infrared to the visible. At ambient pressure the optical energy gap is observed at around 0.5 and 0.3 eV in (NMe4)2TCNQ3 and Cs2TCNQ3, respectively. The energy gap in (NMe4)2TCNQ3 decreases by 0.05 eV with increasing pressure up to 2 GPa, followed by an abrupt decrease towards 0.2 eV between 2 and 3 GPa. At higher pressures up to 5.5 GPa the gap remains almost unchanged. The intra- and inter-molecular optical absorption bands in the near-infrared to visible region are intensified by pressure and broaden out at 2.5 GPa. The absorption spectrum in Cs2TCNQ3 exhibits a similar behavior under pressure. These results suggest that an electronic phase transition is induced by pressure at around 2.5 GPa in both substances. This transition resembles the charge order–disorder (Verwey) transition in Fe3O4.
  physica status solidi (b) 01/2001; 223(1):337 - 342. · 1.32 Impact Factor
• Article: Pressure dependence of charge distribution along TCNQ columns in Cs2TCNQ3

  Hasanudin, Noritaka Kuroda, Tomoko Kagayama, Toyonari Sugimoto, Michihiro Kobayashi, ハサヌディン, ノリタカ クロダ, トモコ カガヤマ, トヨナリ スギモト, ミチヒロ コバヤシ, 規敬 黒田, 朋子 加賀山, 豊成 杉本, 融弘 小林
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  ABSTRACT: Pressure dependence of the charge distribution along the columns of tetracyanoquinodimethane (TCNQ) molecules in Cs2TCNQ3, which is a semiconducting 1/3-filled Hubbard system with the optical energy gap of 0.3 eV at ambient conditions, has been studied by the infrared and visible absorption experiments. An electronic phase transition is found to occur at around 3.5 GPa, in accordance with the previously reported insulator-to-metal transition. Our result suggests that this phase transition accompanies a symmetry change in the relative position of the TCNQ− radical molecules sandwiching the TCNQ0 neutral molecule. In addition, the π* electrons, which are localized on the TCNQ− molecules in the low-pressure phase, are delocalized significantly in the high-pressure phase. However, in the high-pressure phase the π* electrons still maintain the localizing character. The charge-transfer degree of the neutral-like and radical-like molecules of the high-pressure phase is estimated to be ρ = 0.46-0.50 and 0.75-0.77, respectively.
  00319015.
• Source

  Available from: kumamoto-u.ac.jp

  Article: Infrared characterization of GaN films grown on sapphire by MOCVD

  Noritaka Kuroda, Kazuya Saiki, Hasanudin, Junji Watanabe, Meoungwham Cho, ノリタカ クロダ, カズヤ サエキ, ハサヌディン, ジュンヤ ワタナベ, ミョンファン チョ, 規敬 黒田, 和也 佐伯, 純二 渡邉, 明煥 曺, 明煥 曹
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  ABSTRACT: Reststrahlen reflection and attenuated total reflection due to the surface phonon-polariton waves have been measured for 2 µm-thick films of n-GaN deposited on the (0001) surface of sapphire. It has emerged that the lattice of the top 1 µm-thick portion has a high quality while a large strain remains in the inner half of the films. 半導体薄膜内部の結晶品位を非破壊・非接触で評価する技術の開発を目的として、斜入射赤外反射の手法を青色発光ダイオードのためのn-GaN膜に適用し、併せて赤外減衰全反射により結果を検証した。試料には金属有機化学気相堆積法でサファイアの(0001)面上に2 ミクロンの厚さに堆積させた薄膜を用いた。得られた赤外フォノン残留線と表面フォノン波のスペクトルより、膜の上部1 ミクロンは良好な結晶品位を有するが下部の1 ミクロンにはサファイア基板との格子定数差による大きな歪みが残存していることが観測された。これにより、斜入射赤外反射が半導体極薄膜の内部品位評価に大変有効であることが初めて実証された。
• Source

  Available from: reposit.lib.kumamoto-u.ac.jp

  Article: Electronic properties of Cs2TCNQ3 crystals grown under magnetic field

  N. Kuroda, T. Sugimoto, M. Hagiwara, Hasanudin, K. Ueda, T. Tada, H. Uozaki, N. Toyota, I. Mogi, K. Watanabe, M. Motokawa
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  ABSTRACT: The influence of magnetic field on the crystallization process has been examined in Cs2TCNQ3 (TCNQ=tetracyanoquinodimethane), a strongly Coulomb-correlated organic semiconductor. The crystal structure is unaffected by the magnetic field, while the electric, magnetic and optical properties change markedly if the magnetic field higher than a threshold (∼4 T) is applied during the crystal growth. The high-field crystals exhibit a very weak but distinct spontaneous magnetization with the exceedingly high Curie temperature of ∼420 K. The infrared and visible spectroscopy data show that this novel ferromagnetism concurs with the renormalization of the π∗ state of TCNQ radical anions, TCNQ−.
  Synthetic Metals · 1.83 Impact Factor
• Article: High-pressure infrared absorption in Cs2TCNQ3 crystals grown under magnetic field

  Hasanudin, Noritaka Kuroda, Toyonari Sugimoto, Iwao Mogi, Kazuo Watanabe, ハサヌディン, ノリタカ クロダ, トヨナリ スギモト, イワオ モギ, カズオ ワタナベ, 規敬 黒田, 豊成 杉本, 巌 茂木, 和雄 渡辺
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  ABSTRACT: Pressure dependence of infrared absorption has been measured in Cs2TCNQ3 single crystals grown under magnetic field of 5 T (5 T crystals). The behavior of the C-CN as well as C-H stretching modes suggest that there occurs a phase transition which resembles to the one related to the insulator to metal transition in the crystals grown without magnetic field (0 T crystals). This transition, however, takes place at 4.1 GPa, slightly higher than the case of 0 T crystals. The charge transfer degree of the neutral and radical molecules are found to be ρ = 0.30-0.37 and 0.81-0.85, respectively, which are significantly different from that of 0 T crystals. These differences are suggested to arise from the changes in the relative positions of the TCNQ molecules, as indicated from the behavior of the EMV mode.
  03796779.
• Article: Temperature dependence of electronic optical absorption in (NMe4+· TCNQ-·)2TCNQ

  Noritaka Kuroda, Hasanudin, Toyonari Sugimoto, Kazumasa Ueda, Masayoshi Kohama, Naoki Toyota, ノリタカ クロダ, ハサヌディン, トヨナリ スギモト, カズマサ ウエダ, マサヨシ コハマ, ナオキ トヨタ, 規敬 黒田, 豊成 杉本, 一正 植田, 雅圭 小浜, 直樹 豊田
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  ABSTRACT: The temperature dependence of the linearly polarized optical absorption spectrum has been measured in single crystals of (NMe4+·TCNQ−·)2TCNQ, where NMe4 and TCNQ are tetramethylammonium and tetracyanoqui nodi methane, respectively, in the temperature range between −100 and +150 ℃. In addition to intense TCNQ−· dimer bands, strongly temperature-dependent satellite bands appear at around 1.3 eV and 1.9 eV. The singular behavior of the intensity and peak position of the 1.3 eV band shows that a second order phase transition takes place at 126 ℃. The origin of this band is discussed in relation to the mechanism of the phase transition.
  03796779.
• Source

  Available from: Masateru Taniguchi

  Article: Infrared spectroscopy on poly(dG)-poly(dC) DNA at low hydration

  Hasanudin, Kenji Tajiri, Hiroyuki Yokoi, Noritaka Kuroda, Hiroshi Matsui, Takeshi Yanagimachi, Masateru Taniguchi, Tomoji Kawai, Naoki Toyota, ハサヌディン, [......], トモジ カワイ, ナオキ トヨタ, 健治 田尻, 裕之 横井, 規敬 黒田, 広志 松井, 武志 柳町, 正輝 谷口, 知二 川合, 直樹 豊田
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  ABSTRACT: Infrared absorption measurements have been made on dry samples of poly(dG)-poly(dC) DNA at various relative humidity and temperatures. The water content, controlled by the relative humidity, reduces as temperature increases and reaches a very low value of ～ 0.1 wpn above 120℃. This minimum water content is maintained when the samples are brought back to room temperature as long as they are kept at the relative humidity of ～0 %. The molecular vibrations, which characterize the backbone structure as well as the base stacking and pairing, indicate that our samples maintain an A-form double helical structure at all the values of water content. The disorder in the base stacking is observed as the result of the decrease of the water content. Additionally the denaturation appears at high temperatures above 100℃, which reversibly disappears with decreasing temperature.
  00319015.
• Article: Infrared study on pressure-induced charge delocalization in Cs2TCNQ3

  Hasanudin, Noritaka Kuroda, Tomoko Kagayama, Toyonari Sugimoto, ハサヌディン, ノリタカ クロダ, トモコ カガヤマ, トヨナリ スギモト, 規敬 黒田, 朋子 加賀山, 豊成 杉本
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  ABSTRACT: Pressure dependence of several molecular vibration modes in Cs2TCNQ3 has been observed through the infrared absorption measurements. The behavior of the C-CN and C-H stretching modes suggests that phase transition takes place at around 3.6 GPa. The π* electrons, which are localized on TCNQ- molecules in the low-pressure phase, are delocalized significantly in the high-pressure phase. However, the radical-like and neutral-like molecules still coexist in the high-pressure phase indicating that the electrons are not completely delocalized. The electron-molecular-vibration (emv) coupled mode disappears in the high-pressure phase in coincident with the disappearance of the inter-radical charge transfer band S1, proving the strong coupling between them.
  09538984.
• Article: Pressure dependence of electron distribution along the TCNQ columns in (TEDA)2TCNQ3

  Hasanudin, Noritaka Kuroda, Toyonari Sugimoto, ハサヌディン, ノリタカ クロダ, トヨナリ スギモト, 規敬 黒田, 豊成 杉本
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  ABSTRACT: High-pressure infrared absorption has been measured in the single crystals of (TEDA)2TCNQ3 at room temperature. An energy gap of a direct type with the size of approximately 0.23 eV is observed at ambient pressure. In the molecular vibration region, the absorption peaks due to the C=C stretching are observed at 1518 and 1504 cm-1, suggesting that the excess electrons are less localized in this substance compared to other 2:3 TCNQ complexes. The behavior of these peaks suggests that a phase transition takes place at 1.0 GPa. In the high-pressure phase the excess electrons tend to be more localized instead of being delocalized as indicated by the increasing of the energy spacing of those modes. The charge transfer degrees of the TCNQ molecules are estimated to be 0.60 and 0.80 (low pressure) and 0.56 and 0.88 (high-pressure phase).
  15421406.
• Article: Infrared study on structural phase transition in (NMe4)2TCNQ3

  Hasanudin, Noritaka Kuroda, Toyonari Sugimoto, ハサヌディン, ノリタカ クロダ, トヨナリ スギモト, 規敬 黒田, 豊成 杉本
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  ABSTRACT: Temperature dependence of linearly polarized infrared absorption spectrum has been measured in (NMe4)2TCNQ3 single crystals. Strongly temperature dependent electron-molecular-vibration coupled bands are observed at 2173, 1576, 1351, and 1170 cm-1. The singular behaviour of the intensity of these bands is discussed in relation to the structural phase transition observed previously by visible to near-infrared optical absorption and X-ray measurements, where the slipped TCNQ radical dimers in the low-temperature phase tend to be eclipsed in the high-temperature phase.
  03796779.
• Article: High pressure optical absorption in Cs2TCNQ3 complexes grown under the influence of magnetic field

  Hasanudin, Noritaka Kuroda, Tomoko Kagayama, Toyonari Sugimoto, Iwao Mogi, Kazuo Watanabe, Mitsuhiro Motokawa, ハサヌディン, ノリタカ クロダ, トモコ カガヤマ, トヨナリ スギモト, イワオ モギ, カズオ ワタナベ, ミツヒロ モトカワ, 規敬 黒田, 朋子 加賀山, 豊成 杉本, 巌 茂木, 和雄 渡辺, 光博 本河
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  ABSTRACT: Crystals of the organic semiconductor Cs2TCNQ3 have been grown under the influence of magnetic field of 5 T and their optical properties have been compared with the crystals grown without magnetic field. The magnetic field effect manifests itself as the enhancement of the intradimer charge transfer band S1, which appears at around 1.3 eV in the E//a polarization. The high-pressure optical absorption measurements have shown that the S1 band of the crystal grown at 5 T contains a new component, which is significantly intensified with increasing pressure up to 1 GPa, but diminishes as pressure increases further up to 4 GPa, and remains constant at higher pressures. This new component is additional to the component of S1 band which has similar properties to that of the crystals grown without magnetic filed, which continuously grows up to 3 GPa and abruptly broadens out at higher pressures. The new component of S1 is strongly linked to the ferromagnetism in this substance.
  08957959.
• Article: High pressure optical absorption in organic semiconductors (NMe4)2TCNQ3 and Cs2TCNQ3

  Hasanudin, Tomoko Kagayama, Noritaka Kuroda, Toyonari Sugimoto, ハサヌディン, トモコ カガヤマ, ノリタカ クロダ, トヨナリ スギモト, 朋子 加賀山, 規敬 黒田, 豊成 杉本
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  ABSTRACT: The pressure dependence of the optical absorption spectra of (NMe4)2TCNQ3 and Cs2TCNQ3 has been measured at room temperature in the spectral range from mid-infrared to the visible. At ambient pressure the optical energy gap is observed at around 0.5 and 0.3 eV in (NMe4)2TCNQ3 and Cs2TCNQ3, respectively. The energy gap in (NMe4)2TCNQ3 decreases by 0.05 eV with increasing pressure up to 2 GPa, followed by an abrupt decrease towards 0.2 eV between 2 and 3 GPa. At higher pressures up to 5.5 GPa the gap remains almost unchanged. The intra- and inter-molecular optical absorption bands in the near-infrared to visible region are intensified by pressure and broaden out at 2.5 GPa. The absorption spectrum in Cs2TCNQ3 exhibits a similar behavior under pressure. These results suggest that an electronic phase transition is induced by pressure at around 2.5 GPa in both substances. This transition resembles the charge order-disorder (Verwey) transition in Fe3O4.
  03701972.
• Article: Modification of electronic structure of Cs2TCNQ3 with magnetic field

  Hasanudin, Noritaka Kuroda, Toyonari Sugimoto, Masayuki Hagiwara, Kazumasa Ueda, Toshiji Tada, Hiroshi Uozaki, Naoki Toyota, Iwao Mogi, Kazuo Watanabe, [......], カズオ ワタナベ, 規敬 黒田, 豊成 杉本, 政幸 萩原, 一正 植田, 俊治 多田, 寛 夘尾崎, 直樹 豊田, 巌 茂木, 和雄 渡辺
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  ABSTRACT: The crystals of the organic semiconductor Cs2TCNQ3 have been successfully grown under strong external magnetic field, and their properties are compared with those of the crystals grown without magnetic field. The crystals grown under magnetic field higher than a certain temperature-dependent threshold field show remarkable change in electric, magnetic, and optical properties, despite no significant change in the crystal morphology and structure. Electric conductance data suggest the increasing of acceptors in the crystals grown under magnetic field, which is accompanied by the increasing of the Curie temperature by the amount of 100 K., and the intensification of the absorption band arises from inter-radical charge transfer transition. These results suggest that some newly electronic states have been induced by the applied field during the crystal growth.
  00235334.
• Article: Electronic properties of Cs2TCNQ3 crystals grown under magnetic field

  Noritaka Kuroda, Toyonari Sugimoto, Masayuki Hagiwara, Hasanudin, Kazumasa Ueda, Toshiji Tada, Hiroshi Uozaki, Naoki Toyota, Iwao Mogi, Kazuo Watanabe, [......], 規敬 黒田, 豊成 杉本, 政幸 萩原, 一正 植田, 俊治 多田, 崎寛 夘尾, 直樹 豊田, 巌 茂木, 和雄 渡辺, 光博 本河
  [show abstract] [hide abstract]
  ABSTRACT: The influence of magnetic field on the crystallization process has been examined in Cs2TCNQ3 (TCNQ = tetracyaniquinodimethane), a strongly Coulomb-correlated organic semiconductor. The crystal structure is unaffected by the magnetic field, while the electric, magnetic and optical properties change markedly if the magnetic field higher than a threshold (～ 4 T) is applied during the crystal growth. The high-field crystals exhibit a very weak but distinct spontaneous magnetization with the exceedingly high Curie temperature of ～ 420 K. The infrared and visible spectroscopy data show that this novel ferromagnetism concurs with the renormalization of the π* state of TCNQ radical anions, TCNQ-.
  03796779.