Research activity information

• Apr. 2016 公益社団法人応用物理学会, APEX/JJAP編集貢献賞

  北村 雅季

• Identification of exfoliated monolayer hexagonal boron nitride films with a digital color camera under white light illumination

  Yoshiaki Hattori, Takashi Taniguchi, Kenji Watanabe, Masatoshi Kitamura

  Abstract Optical microscopy with white light illumination has been employed when obtaining exfoliated monolayer hexagonal boron nitride (1L hBN) films from a large number of randomly placed films on a substrate. However, real-time observation of 1L hBN using a color camera under white light illumination remains challenging since hBN is transparent in the visible wavelength range. The poor optical constant of 1L hBN films in microphotographs is significantly improved using a Si substrate coated with a SiNx thin-film (SiNx/Si). When observing hBN thin films on SiNx/Si using a color digital camera in an optical microscope under white light illumination, the clarity of the captured images depends on the thickness of the SiNx film (d). For direct real-time observation, the d was optimized based on quantitative chromatic studies tailored to Bayer filters of a color image sensor. Through image simulation, it was determined that the color difference between 1L hBN and the bare substrate is maximized at d = 59 or 70 nm, which was experimentally verified. The SiNx/Si with optimized d values visualized 1L hBN films without requiring significant contrast enhancement via image processing under white light illumination in real-time. Furthermore, the captured color photographs facilitate the reliable determination of the number of layers in few-layer hBN films using the contrast of the green channel of the images.

  Last, IOP Publishing, Jun. 2024, Nanotechnology, English

  [Refereed]

  Scientific journal


• Surface properties of an InGaZnO₄ layer with a monolayer formed using a phosphonic acid: wettability, work function, and thermal stability

  Yudai Kitano, Yoshiaki Hattori, Masatoshi Kitamura

  Abstract The surface properties of an InGaZnO₄ (IGZO) layer with a monolayer formed on the surface using octadecyl phosphonic acid (ODPA) or (1H, 1H, 2H, 2H-heptadecafluorodecyl) phosphonic acid (FDPA) were investigated. Surface roughness, wettability, and work function were investigated using atomic force microscopy, water contact angle measurement, and photoelectron yield spectroscopy, respectively. The reaction time of monolayer formation on an IGZO layer was discussed based on the measured contact angle. An ODPA-monolayer formed at a slightly higher rate than an FDPA-monolayer. The work function measurement provided an estimate of the density of the molecule in the monolayer. Furthermore, the measured contact angle was used to evaluate the thermal stability of a monolayer. The evaluation suggested that annealing above 500 K causes monolayer desorption for both ODPA- and FDPA-monolayers.

  IOP Publishing, Dec. 2023, Japanese Journal of Applied Physics, 63(1) (1), 01SP32 - 01SP32, English

  [Refereed]

  Scientific journal


• Antireflection Substrates for Determining the Number of Layers of Few-Layer Hexagonal Boron Nitride Films and for Visualizing Organic Monolayers

  Yoshiaki Hattori, Takashi Taniguchi, Kenji Watanabe, Masatoshi Kitamura

  Last, American Chemical Society (ACS), Oct. 2023, ACS Applied Nano Materials, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Identification of the monolayer thickness difference in a mechanically exfoliated thick flake of hexagonal boron nitride and graphite for van der Waals heterostructures

  Yoshiaki Hattori, Takashi Taniguchi, Kenji Watanabe, Masatoshi Kitamura

  Abstract Exfoliated flakes of layered materials, such as hexagonal boron nitride (hBN) and graphite with a thickness of several tens of nanometers, are used to construct van der Waals heterostructures. A flake with a desirable thickness, size, and shape is often selected from many exfoliated flakes placed randomly on a substrate using an optical microscope. This study examined the visualization of thick hBN and graphite flakes on SiO₂/Si substrates through calculations and experiments. In particular, the study analyzed areas with different atomic layer thicknesses in a flake. For visualization, the SiO₂ thickness was optimized based on the calculation. As an experimental result, the area with different thicknesses in a hBN flake showed different brightness in the image obtained using an optical microscope with a narrow band-pass filter. The maximum contrast was 12% with respect to the difference of monolayer thickness. In addition, hBN and graphite flakes were observed by differential interference contrast (DIC) microscopy. In the observation, the area with different thicknesses exhibited different brightnesses and colors. Adjusting the DIC bias had a similar effect to selecting a wavelength using a narrow band-pass filter.

  Last, IOP Publishing, May 2023, Nanotechnology, 34(29) (29), 295701 - 295701, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Orthogonal electric and ionic conductivities in the thin film of thiophene–thiophene block copolymer

  Sonoka Yamamoto, Ryutaro Yamashita, Chihiro Kubota, Kentaro Okano, M. Kitamura, Masahiro Funahashi, SyuCheng Ye, Yung-Tin Pan, Masaki Horie, Takuji Shintani, Hironori Murata, Hideto Matsuyama, Atsunori Mori

  Thiophene–thiophene block copolymer composed of hydrophilic and hydrophobic side chain functionalities was designed and synthesized. Deprotonative metalation nickel-catalyzed polymerization protocol successfully afforded the block copolymer, which side chains are derived...

  Royal Society of Chemistry (RSC), Jan. 2023, Journal of Materials Chemistry C, 11(7) (7), 2484 - 2493, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Reflected light microscopy of a gold oxide layer formed on a Au film by ultraviolet/ozone treatment

  Yoshiaki Hattori, Masatoshi Kitamura

  Last, Elsevier BV, Jan. 2023, Thin Solid Films, 764, 139631 - 139631, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Enhancement of the contrast for a hexagonal boron nitride monolayer placed on a silicon nitride/silicon substrate

  Yoshiaki Hattori, Takashi Taniguchi, Kenji Watanabe, Masatoshi Kitamura

  Abstract We propose a visualization technique for identifying an exfoliated monolayer hexagonal boron nitride (hBN) flake placed on a SiN_x/Si substrate. The use of a Si substrate with a 63 nm thick SiN_x film enhanced the contrast of monolayer hBN at wavelengths of 480 and 530 nm by up to 12% and −12%, respectively. The maximum contrast for the Si substrate with SiN_x is more than four times as large as that for a Si substrate with a ∼90 or ∼300 nm SiO₂ film. Based on the results of the reflectance spectrum measurement and numerical calculations, the enhancement is discussed.

  Last, IOP Publishing, Aug. 2022, Applied Physics Express, 15(8) (8), 086502 - 086502, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Organic monolayers modified by vacuum ultraviolet irradiation for solution-processed organic thin-film transistors

  Satoshi Inoue, Yoshiaki Hattori, Masatoshi Kitamura

  A trimethylsilyl-monolayer modified by vacuum ultraviolet (VUV) light has been investigated for use in solution-processed organic thin-film transistors (OTFTs). The VUV irradiation changed a hydrophobic trimethylsilyl-monolayer formed from hexamethyldisilazane vapor into a hydrophilic surface suitable for solution processing. The treated surface was examined via water contact angle measurement and X-ray photoelectron spectroscopy. An appropriate irradiation of VUV light enabled the formation of a dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C₈-BTBT) film on a modified monolayer by spin-coating. Consequently, the C₈-BTBT-based OTFT with a monolayer modified for an optimal VUV irradiation time exhibited a field-effect mobility up to 4.76 cm² V⁻¹ s⁻¹. The partial monolayer modification with VUV can be adapted to a variety of solution-processes and organic semiconductors for prospective printed electronics.

  Corresponding, IOP Publishing, Jun. 2022, Japanese Journal of Applied Physics, 61(SE) (SE), SE1012 - SE1012, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Visualization of a hexagonal born nitride monolayer on an ultra-thin gold film via reflected light microscopy

  Yoshiaki Hattori, Takashi Taniguchi, Kenji Watanabe, Masatoshi Kitamura

  Hexagonal boron nitride (h-BN) is an important insulating layered material for two-dimensional heterostructure devices. Among many applications, few-layer h-BN films have been employed as superior tunneling barrier films. However, it is difficult to construct a heterostructure with ultra-thin h-BN owing to the poor visibility of flakes on substrates, especially on a metallic surface substrate. Since reflectance from a metallic surface is generally high, a h-BN film on a metallic surface does not largely influence reflection spectra. In the present study, a thin Au layer with a thickness of ∼10 nm deposited on a Si substrate with a thermally grown SiO₂ was used for visualizing h-BN flakes. The thin Au layer possesses conductivity and transparency. Thus, the Au/SiO₂/Si structure serves as an electrode and contributes to the visualization of an ultra-thin film according to optical interference. As a demonstration, the wavelength-dependent contrast of exfoliated few-layer h-BN flakes on the substrate was investigated under a quasi-monochromatic light using an optical microscope. A monolayer h-BN film was recognized in the image taken by a standard digital camera using a narrow band-pass filter of 490 nm, providing maximum contrast. Since the contrast increases linearly with the number of layers, the appropriate number of layers is identified from the contrast. Furthermore, the insulating property of a h-BN flake is examined using a conductive atomic force microscope to confirm whether the thin Au layer serves as an electrode. The tunneling current through the h-BN flake is consistent with the number of layers estimated from the contrast.

  Last, IOP Publishing, Feb. 2022, Nanotechnology, 33(6) (6), 065702 - 065702

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Chain-Length Dependence of Optical Properties for an Alkanethiol Monolayer on an Ultrathin Gold Film Revealed via Reflected Light Microscopy

  Yoshiaki Hattori, Hayato Takahashi, Naoki Ikematsu, Masatoshi Kitamura

  American Chemical Society (ACS), Jul. 2021, The Journal of Physical Chemistry C, 125(27) (27), 14991 - 14999

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Polarization Raman Imaging of Organic Monolayer Islands for Crystal Orientation Analysis

  Toki Moriyama, Takayuki Umakoshi, Yoshiaki Hattori, Koki Taguchi, Prabhat Verma, Masatoshi Kitamura

  American Chemical Society (ACS), Apr. 2021, ACS Omega, 6(14) (14), 9520 - 9527

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Energy distribution of interface states generated by oxygen plasma treatment for control of threshold voltage in pentacene thin-film transistors

  Yoshinari Kimura, Yoshiaki Hattori, Masatoshi Kitamura

  IOP Publishing, Sep. 2020, Journal of Physics D: Applied Physics

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Crystal Orientation Imaging of Organic Monolayer Islands by Polarized Light Microscopy

  Yoshiaki Hattori, Masatoshi Kitamura

  American Chemical Society ({ACS}), Aug. 2020, ACS Applied Materials & Interfaces, 12(32) (32), 36428 - 36436

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• A 42 mV startup ring oscillator using gain-enhanced self-bias inverters for extremely low voltage energy harvesting

  Ryo Matsuzuka, Tatsuya Terada, Kaori Matsumoto, Masatoshi Kitamura, Tetsuya Hirose

  IOP Publishing, Apr. 2020, Japanese Journal of Applied Physics, 59(SG) (SG), SGGL01 - SGGL01, English

  [Refereed]

  Scientific journal


• Formation of a mixed monolayer on a gold surface using fluorobenzenethiol and alkanethiol

  Naoki Ikematsu, Hayato Takahashi, Yoshiaki Hattori, Masatoshi Kitamura

  Corresponding, IOP Publishing, Mar. 2020, Japanese Journal of Applied Physics, 59(SD) (SD), SDDA09 - SDDA09, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Formation of a monolayer on a gold surface with high thermal stability using benzenedithiol

  Hayato Takahashi, Naoki Ikematsu, Yoshiaki Hattori, Masatoshi Kitamura

  Corresponding, IOP Publishing, Mar. 2020, Japanese Journal of Applied Physics, 59(SD) (SD), SDDA03 - SDDA03, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Evaluation of organic metal-oxide-semiconductor capacitors based on a distributed constant circuit

  Yoshinari Kimura, Yoshiaki Hattori, Masatoshi Kitamura

  Corresponding, IOP Publishing, Mar. 2020, Japanese Journal of Applied Physics, 59(3) (3), 036503 - 036503, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Wide-range work function tuning in gold surfaces modified with fluorobenzenethiols toward application to organic thin-film transistors

  Takumi Yoshioka, Hiroki Fujita, Yoshinari Kimura, Yoshiaki Hattori, Masatoshi Kitamura

  {IOP} Publishing, Feb. 2020, Flexible and Printed Electronics

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Nucleation Density and Shape of Submonolayer Two-Dimensional Islands of Diphenyl Dinaphthothienothiophene in Vacuum Deposition

  Hattori, Yoshiaki, Kimura, Yoshinari, Kitamura, Masatoshi

  Submonolayer two-dimensional (2D) islands of diphenyl dinaphthothienothiophene with various shapes and densities (N) were formed on a SiO2/Si substrate by controlling substrate temperature and the surface treatment for SiO2 in vacuum deposition to investigate the growth mechanism on the basis of their morphology. The statistical analysis shows that the 2D islands have complex shapes when N is small, and there is a constant relationship between N and the shape complexity of the 2D islands, regardless of the deposition conditions. Because the surface morphology is determined by diffusion coefficients for admolecules on a substrate surface (D-s) and along the edge of a 2D island (D-edg), the relationship between (N, shape complexity) and (D-s, D-edg) is studied. The statistical analysis indicates that D-edg is almost independent of the surface conditions and is instead determined by interactions with molecules constructing the 2D island. Therefore, D-edg is considered as a material-dependent parameter to control the morphology for growing high-quality films in vacuum deposition.

  AMER CHEMICAL SOC, Jan. 2020, JOURNAL OF PHYSICAL CHEMISTRY C, 124(1) (1), 1064 - 1069, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• The growth mechanism and characterization of few-layer diphenyl dinaphthothienothiophene films prepared by vacuum deposition

  Hattori, Yoshiaki, Kimura, Yoshinari, Yoshioka, Takumi, Kitamura, Masatoshi

  The growth mechanism of 2,9-diphenyl-dinaphtho [2,3-b:2',3'-f]thieno [3,2-b]thiophene (DPh-DNTT) thin-films prepared by vacuum deposition was investigated based on the morphological crystallinity of the obtained films. In addition to atomic force microscopy, which is commonly used for imaging surface morphology, optical microscopy was also positively used for the same purpose. The technique allows the quick and easy evaluation of thin films. The optical microscopy images show that DPh-DNTT films grew according to a layer-by-layer growth mode. Each layer grew as flat two-dimensional (2D) islands with a thickness of about 2.3 nm, where DPh-DNTT molecules stand almost vertically on the substrate. The height difference between layers provided a color contrast in these images, which visualizes the initial 2D island on the Si substrate with thermally grown SiO2 and fractal-shape 2D islands on top surface. By using the method, a monolayer of isolated and round 2D islands, with a diameter of approximately 4 mu m, formed at a high substrate temperature on a SiO2 surface that had been previously treated with O-2 plasma or UV-O-3. The presence of a DPh-DNTT layer on the substrate was also confirmed by micro-Raman measurement.

  ELSEVIER, Nov. 2019, ORGANIC ELECTRONICS, 74, 245 - 250, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Data on optical microscopy and vibrational modes in Diphenyl Dinaphthothienothiophene thin films

  Hattori, Yoshiaki, Kimura, Yoshinari, Yoshioka, Takumi, Kitamura, Masatoshi

  The thin-films of 2,9-diphenyl-dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DPh-DNTT) prepared by vacuum deposition was observed by the optical microsope. By applying the dark-field mode in observation and/or image processing after imaging appropriately, morphological structure with a resolution of a few nanometers height was visualized easily and quickly. The technique can be used in a similar to atomic force microscopy, which is commonly used for imaging surface morphology. Moreover, the vibrational modes of a DPh-DNTT molecule calculated by quantum chemistry program is described as well as the comparison of the experimental Raman spectra for identification. The presented data are produced as part of the main work entitled "The Growth Mechanism and Characterization of Few-layer Diphenyl Dinaphthothienothiophene Films Prepared by Vacuum Deposition" (Hattori et al., 2019). (C) 2019 The Author(s). Published by Elsevier Inc.

  ELSEVIER, Oct. 2019, DATA IN BRIEF, 26, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Voltage and Frequency Dependence of Capacitance Characteristics in Organic MOS Capacitors

  Yoshinari Kimura, Yoshiaki Hattori, Masatoshi Kitamura

  Pentacene metal-oxide-semiconductor capacitors having a channel area uncovered with the top electrode have been examined by capacitance-voltage (C-V) and capacitance-frequency (C-f) measurements. The C-V and C-f characteristics were reproduced using an equivalent circuit based on a distributed constant circuit. The sheet resistance, which characterizes carrier transport in the pentacene film, was obtained as a sheet resistance included in the equivalent circuit reproducing the measured characteristics.

  May 2019, 2019 Compound Semiconductor Week, CSW 2019 - Proceedings

  International conference proceedings


• Nucleation and shape of 2D islands of DPh-DNTT thin-films prepared by vacuum evaporation

  Yoshiaki Hattori, Yoshinari Kimura, Masatoshi Kitamura

  The growth mechanism of 2,9-diphenyl-dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DPh-DNTT) thin-films prepared by vacuum evaporation was investigated from a view point of the morphological crystallinity. In addition to atomic force microscopy, which is commonly used for imaging the morphology of surfaces, optical microscopy was positively used for the same purpose. The method allows quick and easy evaluation of the thin-film. In fact, an isolated, round, monolayer 2D island on the SiO2 substrate in initial stage and fractal-shape 2D islands on top surface of thin-film were observed. The nucleation density which depends on substrate temperature and surface treatment was investigated to clarified the growth mechanism.

  May 2019, 2019 Compound Semiconductor Week, CSW 2019 - Proceedings

  International conference proceedings


• A ring oscillator consisting of pentacene thin-film transistors with controlled threshold voltages

  Hajime Takahashi, Masatoshi Kitamura, Yoshiaki Hattori, Yoshinari Kimura

  Pentacene thin-film transistors (TFTs) with controlled threshold voltages have been applied to a ring oscillator consisting of enhancement/depletion inverters for evaluation of the dynamic characteristics. The threshold voltage control was demonstrated by using oxygen plasma treatment to the SiO2 gate dielectric prepared by rf sputtering. The surface roughness of the SiO2 gate dielectric depended on the sputtering condition. The use of flat SiO2 gate dielectrics contributed to the improvement of the field-effect mobilities in pentacene TFTs. As a result, the ring oscillator operated at supply voltages of 15-25 V. The oscillation frequency was consistent with the result of circuit simulation for the ring oscillator. (C) 2019 The Japan Society of Applied Physics

  IOP PUBLISHING LTD, Apr. 2019, JAPANESE JOURNAL OF APPLIED PHYSICS, 58, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Application of pentacene thin-film transistors with controlled threshold voltages to enhancement/depletion inverters

  Hajime Takahashi, Yuki Hanafusa, Yoshinari Kimura, Masatoshi Kitamura

  Oxygen plasma treatment has been carried out to control the threshold voltage in organic thin-film transistors (TFTs) having a SiO2 gate dielectric prepared by rf sputtering. The threshold voltage linearly changed in the range of -3.7 to 3.1 V with the increase in plasma treatment time. Although the amount of change is smaller than that for organic TFTs having thermally grown SiO2, the tendency of the change was similar to that for thermally grown SiO2. To realize different plasma treatment times on the same substrate, a certain region on the SiO2 surface was selected using a shadow mask, and was treated with oxygen plasma. Using the process, organic TFTs with negative threshold voltages and those with positive threshold voltages were fabricated on the same substrate. As a result, enhancement/depletion inverters consisting of the organic TFTs operated at supply voltages of 5 to 15V. (C) 2018 The Japan Society of Applied Physics

  IOP PUBLISHING LTD, Mar. 2018, JAPANESE JOURNAL OF APPLIED PHYSICS, 57(3) (3), 03EH03-1 - 03EH03-5, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• 論理回路応用のための有機トランジスタ

  KITAMURA Masatoshi

  応用物理学会, Feb. 2017, 応用物理, 86(2) (2), 122 - 126, Japanese

  [Refereed]

  Scientific journal


• Material Production Technology for Oxide Semiconductor Gas Sensors: Recent Research Progress

  Masatoshi KITAMURA

  Oxide-semiconductor based gas sensors have been intensively investigated in order to improve the sensitivity and selectivity of a certain gas. This article reviews the recent research progress of gas sensors having oxide semiconductor as an active layer, in particular detecting for H₂ and volatile organic compounds. The semiconductor material for gas sensors reported in this article includes SnO₂, WO₃, ZnO, In₂O₃, and NiO. The sensitivity of gas sensors having different structures and semiconductors is compared.
  

  Corresponding, The Vacuum Society of Japan, Feb. 2017, Journal of the Vacuum Society of Japan, 60(11) (11), 415 - 420, Japanese

  [Refereed]

  Scientific journal


• Organic-lead halide perovskite solar cell with ITO transparent electrode deposited by sputtering process

  Takumi Matsuda, Yoshikazu Tateishi, Kenichi Yamashita, Masatoshi Kitamura, Takashi Kita

  © 2016 The Society of Materials Science, Japan. Thin film solar cells using perovskite materials are very intensively studied since the perovskite materials such as CH3NH3PbI3 crystal have been found to show sensitizing effects on a TiO2 electron transport layer. This class of solar cell has made tremendous progress during the last few years, leading to a recently certified record power conversion efficiency (PCE) of 21.02%. In the perovskite /crystalline-Si (c-Si) tandem solar cell, furthermore, the theoretical value of PCE is expected as large as 35 %. Toward this application, the perovskite solar cell must be highly transparent at near-infrared wavelengths so that sufficient light is transmitted to the narrow-bandgap bottom cell. In this study, we fabricated the organic-lead halide perovskite solar cells comprising a transparent sputtered indium tin oxide (ITO) top electrode. We observed the PCE of 1.5% in transparent perovskite solar cells with a thin molybdenum oxide buffer layer and ITO electrode. Moreover, we obtained the PCE of 2% even in solar cells with ITO electrode sputtered directly on the organic charge transport layer. The photovoltaic property could be confirmed under the light irradiation from the ITO top electrode side.

  Sep. 2016, Zairyo/Journal of the Society of Materials Science, Japan, 65(9) (9), 642 - 646, Japanese

  [Refereed]

  Scientific journal


• Wettability Control of Gold Surfaces Modified with Benzenethiol Derivatives: Water Contact Angle and Thermal Stability

  Shingo Tatara, Yasutaka Kuzumoto, Masatoshi Kitamura

  The water wettability of Au surfaces has been controlled using various benzenethiol derivatives including 4-methylbenzenethiol, pentafluorobenzenethiol, 4-fluorobenzenethiol, 4-methoxybenzenethiol, 4-nitrobenzenethiol, and 4-hydroxybenzenethiol. The water contact angle of the Au surface modified with the benzenethiol derivative was found to vary in the wide range of 30.9 degrees to 88.3 degrees. The contact angle of the modified Au films annealed was also measured in order to investigate their thermal stability. The change in the contact angle indicated that the modified surface is stable at temperatures below about 400 K. Meanwhile, the activation energy of desorption from the modified surface was estimated from the change in the contact angle. The modified Au surface was also examined using X-ray photoelectron spectrosocopy.

  AMER SCIENTIFIC PUBLISHERS, Apr. 2016, JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 16(4) (4), 3295 - 3300, English

  [Refereed]

  Scientific journal


• Threshold voltage control in dinaphthothienothiophene-based organic transistors by plasma treatment: Toward their application to logic circuits

  Asahi Kitani, Yoshinari Kimura, Masatoshi Kitamura, Yasuhiko Arakawa

  The threshold voltage in p-channel organic thin-film transistors ( TFTs) having dinaphthothienothiophene as a channel material has been investigated toward their applicability to logic circuits. Oxygen plasma treatment of the gate dielectric surface was carried out to control the threshold voltage. The threshold voltage changed in the range from -6.4 to 9.4V, depending on plasma treatment time and the thickness of the gate dielectric. The surface charge after plasma treatment was estimated from the dependence of the threshold voltage. Operation of logic inverters consisting of TFTs with different threshold voltages was demonstrated as an application of TFTs with controlled threshold voltage. (C) 2016 The Japan Society of Applied Physics

  IOP PUBLISHING LTD, Mar. 2016, JAPANESE JOURNAL OF APPLIED PHYSICS, 55(3) (3), English

  [Refereed]

  Scientific journal


• Surface properties of substituted-benzenethiol monolayers on gold and silver: Work function, wettability, and surface tension

  Shingo Tatara, Yasutaka Kuzumoto, Masatoshi Kitamura

  The surface properties, including work function and wettability, of Au and Ag surfaces modified with various substituted benzenethiols have been investigated. Whereas the work functions of the modified Au surfaces ranged from 4.42 to 5.48 eV, those of the modified Ag surfaces ranged from 3.99 to 5.77 eV. The highest work function of 5.77 eV was obtained on the Ag surface modified with pentafluorobenzenethiol, and the lowest work function of 3.99 eV was obtained on the Ag surface modified with 4-methylbenzenethiol. The water contact angle on modified Au surfaces was found to be in a wide range from 30.9 to 88.3 degrees. The water contact angle on the Au surface modified with a substituted benzenethiol was close to that on the Ag surface modified with the same benzenethiol. Furthermore, the tension of the modified Au surfaces was estimated from their contact angles of water and ethylene glycol. (C) 2016 The Japan Society of Applied Physics

  IOP PUBLISHING LTD, Mar. 2016, JAPANESE JOURNAL OF APPLIED PHYSICS, 55(3) (3), English

  [Refereed]

  Scientific journal


• Operational stability in pentacene thin-film transistors with threshold voltages tuned by oxygen plasma treatment

  Yoshinari Kimura, Masatoshi Kitamura, Asahi Kitani, Yasuhiko Arakawa

  Pentacene-based organic thin-film transistors (TFTs) having a SiO2 gate dielectric treated with oxygen plasma have been investigated for control of the threshold voltage. The threshold voltage changed in the wide range from % 15 to 80V, depending on plasma treatment time, AC power for plasma generation, and gate dielectric thickness. The threshold voltage change was attributed to negative charges induced on and/or near the surface of the gate dielectric. The threshold voltage change on the order of 1 V was particularly proportional to plasma treatment time. The predictable change enables the control of threshold voltage in this range. In addition, the effect of gate bias stress on threshold voltage was examined. The results suggested that gate bias stress does not negate the threshold voltage change induced by plasma treatment. (C) 2016 The Japan Society of Applied Physics

  IOP PUBLISHING LTD, Feb. 2016, JAPANESE JOURNAL OF APPLIED PHYSICS, 55(2) (2), English

  [Refereed]

  Scientific journal


• Structural and electrical properties of fluorinated copper phthalocyanine toward organic photovoltaics: Post-annealing effect under pressure

  Yasutaka Kuzumoto, Hirotaka Matsuyama, Masatoshi Kitamura

  The morphology and current-voltage characteristics of organic films with copper phthalocyanine (CuPc) and hexadecafluoro CuPc (F16CuPc) prepared under different conditions have been investigated. Substrate heating improved the current-voltage characteristics of CuPc single-layer devices. Also, substrate heating from room temperature suppressed breakdown at low voltages in F16CuPc devices. In addition, the post-annealing effects under pressure on the current-voltage characteristics of CuPc/F16CuPc devices were investigated. Although a CuPc/F16CuPc device prepared at a substrate temperature of 120 degrees C exhibited a reverse rectifying property and provided no photocurrent, a CuPc/F16CuPc device post-annealed at 300 degrees C under pressure showed a normal rectifying property and worked as a photovoltaic cell. (C) 2014 The Japan Society of Applied Physics

  IOP PUBLISHING LTD, Apr. 2014, JAPANESE JOURNAL OF APPLIED PHYSICS, 53(4) (4), 1 - 4, English

  [Refereed]

  Scientific journal


• Work function of gold surfaces modified using substituted benzenethiols: Reaction time dependence and thermal stability

  Yasutaka Kuzumoto, Masatoshi Kitamura

  The work function of Au surfaces modified with various substituted benzenethiols has been systematically investigated for application to the design of organic electronic devices. The work function was found to vary in the range of 4.37 to 5.48 eV depending on the substituted benzenetniol used, which included pentafluorobenzenethiol, 4-fluorobenienethiol, 4-methylbenzenethiol, 4-aminobenzenethiol, and 4-(dimethylamina)benzenethiol. Subsequent thermal annealing of the modified Au films above 373 K changed the work function back to that of an unmodified Au surface. Meanwhile, thermal desorption spectroscopy revealed species desorbing from the modified Au surfaces, indicating cleavage of the C S bond as well as the S Au bond. (C) 2014 The Japan Society of Applied Physics

  IOP PUBLISHING LTD, Mar. 2014, APPLIED PHYSICS EXPRESS, 7(3) (3), 1 - 35701, English

  [Refereed]

  Scientific journal


• Partially fluorinated copper phthalocyanine toward band engineering for high-efficiency organic photovoltaics

  Yasutaka Kuzumoto, Hirotaka Matsuyama, Masatoshi Kitamura

  The electronic structures of copper phthalocyanine (CuPc) and fluorinated CuPc, FxCuPc (x = 4, 8, 12, and 16), have been investigated by density functional theory. The HOMO and LUMO energies systematically decrease with an increase in the number of fluorine atoms. The degree of the decrease depends on the position of the substitution of hydrogen with fluorine. The HOMO (LUMO) energies vary in the range of -5.33 to -6.82 eV (-3.12 to -4.65 eV). The UV-visible absorption spectra and photoelectron ionization energies of the deposited FxCuPc (x = 0, 8, and 16) thin films are compared with the calculation results. The calculated bandgap energies and HOMO levels are consistent with those obtained from the experimental results. (C) 2014 The Japan Society of Applied Physics

  IOP PUBLISHING LTD, Jan. 2014, JAPANESE JOURNAL OF APPLIED PHYSICS, 53(1) (1), 01AB03, English

  [Refereed]

  Scientific journal


• High performance inkjet-printed C-60 fullerene thin-film transistors: Toward a low-cost and reproducible solution process

  Woogun Kang, Masatoshi Kitamura, Yasuhiko Arakawa

  We have demonstrated high performance inkjet-printed n-channel thin-film transistors (TFTs) using C-60 fullerene as a channel material. Highly uniform amorphous C-60 thin-film patterns were fabricated on a solution-wettable polymer gate dielectric layer by inkjet-printing and vacuum drying process. Fabricated C-60 TFTs shows great reproducibility and high performance; field-effect mobilities of 2.2-2.4 cm(2) V-1 s(-1), threshold voltages of 0.4-0.6 V, subthreshold slopes of 0.11-0.16 V dec(-1) and current on/off ratio of 10(7)-10(8) in a driving voltage of 5 V. This is due to the efficient annealing process that extracting the solvent residue and the formation of low trap-density gate dielectric surface. (C) 2012 Elsevier B. V. All rights reserved.

  ELSEVIER SCIENCE BV, Feb. 2013, ORGANIC ELECTRONICS, 14(2) (2), 644 - 648, English

  [Refereed]

  Scientific journal


• Short-channel, high-mobility organic thin-film transistors with alkylated dinaphthothienothiophene

  Masatoshi Kitamura, Yasutaka Kuzumoto, Yasuhiko Arakawa

  Short-channel, high-mobility organic transistors have been demonstrated using alkylated dinaphthothienothiophene. The field-effect mobility for a transistor with a channel length of 2 mu m was 1.46 cm(2)/Vs at operation of -15 V. The transconductance of the transistor reached to 500 mu S/mm, which is one of the highest values in pchannel organic transistors. The high mobility in short-channel transistors is attributed to low contact resistance caused by Au/AuNi electrodes modified with pentafluorobenzenethiol. An illustration of a fabricated C-10-DNTT thin-film transistor with PFBT-modified electrodes. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  WILEY-V C H VERLAG GMBH, 2013, PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 10, NO 11, 10(11) (11), 1632 - 1635, English

  [Refereed]

  International conference proceedings


• Solution-Processed C-60 Single-Crystal Field-Effect Transistors

  Woogun Kang, Masatoshi Kitamura, Tetsuji Itoh, Yasuhiko Arakawa

  We have demonstrated high mobility C-60 single-crystal field-effect transistors formed by a solution process. 1,2,4-Trichlorobenzene (TCB) C-60 solution formed plate like crystals with sizes exceeding 500 mu m. We found that the C-60 single crystals prepared from solution consist of two TCB molecules per C-60 molecule, with a triclinic crystal structure. TCB molecules in C-60 crystals are extracted by an annealing process, and the crystal structure was changed to a face-centered-cubic structure. The C-60 single crystal prepared from TCB solution showed typical n-channel operation and high electron mobilities of up to 1.4 cm2 V-1 s(-1). (C) 2012 The Japan Society of Applied Physics

  IOP PUBLISHING LTD, Nov. 2012, JAPANESE JOURNAL OF APPLIED PHYSICS, 51(11) (11), 1 - 11, English

  [Refereed]

  Scientific journal


• Solvent Dependence of Vacuum-Dried C-60 Thin-Film Transistors

  Woogun Kang, Masatoshi Kitamura, Masakazu Kamura, Shigeru Aomori, Yasuhiko Arakawa

  We demonstrated solution-processed C-60 thin-film transistors with high electron mobility. C-60 solutions in various organic solvents were dried in a vacuum chamber to obtain uniform thin films. While C-60 solution dried under atmospheric pressure produced a large number of crystals, vacuum-dried C-60 solution provided flat and uniform thin films of sufficiently high quality to fabricate thin-film transistors. In spite of amorphous-like thin-film formation, C-60 transistors showed strong solvent dependence. High performance C-60 thin-film transistors with field-effect mobility of 0.86 cm(2) V-1 s(-1), threshold voltage of 1.5 V, subthreshold slope of 0.67 V/decade and a current on/off ratio of 3.9 x 10(6) were obtained from 1,2,4-trichlorobenzene C-60 solution. (C) 2012 The Japan Society of Applied Physics

  IOP PUBLISHING LTD, Feb. 2012, JAPANESE JOURNAL OF APPLIED PHYSICS, 51(2) (2), 1 - 2, English

  [Refereed]

  Scientific journal


• High performance ink-jet-printed tfts on solution wetting polymer gate dielectric layer

  Woogun Kang, Masatoshi Kitamura, Yasuhiko Arakawa

  We have demonstrated high performance C60 thin-film transistors by inkjet-printing technology.C60 inks was jetted onto a polymer or self-assembled monolayers gate dielectric layer, then vacuum-dried to form uniform thin films. Inkjet-printed C60 thin-film transistors on a polymer gate dielectric layer showed an electron mobility of 1.6 cm2/Vs in operating voltage of 5 V. These results are attributed to high uniformity of vacuum-dried C60 thin films and low charge trap density between C60 thin films and gate dielectric layer interface.

  Blackwell Publishing Ltd, 2012, Digest of Technical Papers - SID International Symposium, 43(1) (1), 1094 - 1096, English

  International conference proceedings


• High Frequency Operation ( > 10 MHz) in Pentacene Thin-Film Transistors

  Masatoshi Kitamura, Yasuhiko Arakawa

  The current-gain cutoff frequency for bottom contact p-channel pentacene thin-film transistors (TFTs) with channel lengths of 2-10 mu m has been investigated. A maximum cutoff frequency of 11.4 MHz was obtained from a pentacene TFT with a channel length of 2 mu m and a saturation mobility of 0.73 cm(2)/Vs.

  Lead, AMER INST PHYSICS, Dec. 2011, AIP Conference Proceedings, 1399(1) (1), 883, English

  [Refereed]

  International conference proceedings


• Novel Solution Process for High-Mobility C-60 Fullerene Field-Effect Transistors

  Woogun Kang, Masatoshi Kitamura, Yasuhiko Arakawa

  Solution-processed C-60 fullerene field-effect transistors with high electron mobility were demonstrated by using a novel drying process. Highly uniform and flat C-60 layers were prepared from a C-60 solution when the solution was rapidly dried in a vacuum chamber. Field-effect transistors with solution-deposited C-60 active layers showed electron mobility of up to 0.86 cm(2) V-1 s(-1), threshold voltage of 3 V, subthreshold slope of 0.67 V/decade, and a current on/off ratio of 4 x 10(6). The mobilities of solution-deposited C-60 transistors were comparable to those of vacuum-deposited C-60 transistors. (C) 2011 The Japan Society of Applied Physics

  JAPAN SOC APPLIED PHYSICS, Dec. 2011, APPLIED PHYSICS EXPRESS, 4(12) (12), 1 - 121602, English

  [Refereed]

  Scientific journal


• 高速動作有機CMOS回路の実現に向けて

  北村 雅季

  Nov. 2011, 応用物理学会 有機分子・バイオエレクトロニクス分科会 会誌, Vol.22 No.4 pp.231-236, Japanese

  Scientific journal


• High-Frequency Organic Complementary Ring Oscillator Operating up to 200 kHz

  Masatoshi Kitamura, Yasutaka Kuzumoto, Shigeru Aomori, Yasuhiko Arakawa

  Organic complementary circuits consisting of bottom-contact p-channel pentacene and n-channel C(60) thin-film transistors (TFTs) have been fabricated to evaluate their dynamic properties. Modified drain and source electrodes were used to balance the threshold voltages of the pentacene and C(60) TFTs. The balanced threshold voltage allowed use of equal-size channel dimensions for both channel-type TFTs in the circuits. The signal delay per stage of a five-stage ring oscillator was consistent with the mobilities of the individual TFTs. The oscillation frequency increased with supply voltage up to 200 kHz, which is the highest frequency in organic five-stage complementary ring oscillators. (C) 2011 The Japan Society of Applied Physics

  JAPAN SOC APPLIED PHYSICS, May 2011, APPLIED PHYSICS EXPRESS, 4(5) (5), 1 - 51601, English

  [Refereed]

  Scientific journal


• 高速動作有機トランジスタに向けた有機無機界面制御

  KITAMURA Masatoshi

  May 2011, 応用物理学会 有機分子・バイオエレクトロニクス分科会 会誌, Vol. 22 No.2 pp.71-74, English

  Scientific journal


• High Current-Gain Cutoff Frequencies above 10MHz in n-Channel C-60 and p-Channel Pentacene Thin-Film Transistors

  Masatoshi Kitamura, Yasuhiko Arakawa

  The current-gain cutoff frequencies for bottom contact n-channel C-60 and p-channel pentacene thin-film transistors (TFTs) with channel lengths of 2-10 mu m have been investigated. The cutoff frequency was estimated by direct measurement of the gate and drain modulation currents. The measured cutoff frequencies for both C-60 and pentacene TFTs increase consistently with reducing channel length. Cutoff frequencies of 27.7 and 11.4 MHz were obtained from C-60 and pentacene TFTs with a channel length of 2 mu m, respectively. (C) 2011 The Japan Society of Applied Physics

  JAPAN SOC APPLIED PHYSICS, Jan. 2011, JAPANESE JOURNAL OF APPLIED PHYSICS, 50(1) (1), 1 - 1, English

  [Refereed]

  Scientific journal


• Synthesis and investigation of pi-conjugated azomethine self-assembled multilayers by layer-by-layer growth

  Masakazu Kamura, Yasutaka Kuzumoto, Shigeru Aomori, Hirohiko Houjou, Masatoshi Kitamura, Yasuhiko Arakawa

  Layer-by-layer formation for pi-conjugated azomethine multilayers bonded on substrates was investigated. The multilayers were synthesized using ethanol (EtOH) and dichloromethane (DCM) as reaction solvents. The multilayer characteristics were analyzed using UV-vis absorption spectroscopy, ellipsometric thickness, and atomic force microscopy. The absorption spectra and ellipsometric thicknesses of multilayers formed using EtOH and DCM were compared. The results indicate that EtOH is more suitable than DCM for such layer-by-layer formation. In addition, bandgaps estimated from the absorption edge of multilayers were investigated. The results indicate that the bandgap decreases as the number of benzene rings contained in the molecular chain of the multilayer increases. Also, a multilayer with four benzene rings bonded on a substrate had a bandgap close to that of a polymer with a similar chemical structure. (c) 2010 Elsevier B.V. All rights reserved.

  ELSEVIER SCIENCE SA, Jul. 2010, THIN SOLID FILMS, 518(18) (18), 5115 - 5120, English

  [Refereed]

  Scientific journal


• High conductance bottom-contact pentacene thin-film transistors with gold-nickel adhesion layers

  Masatoshi Kitamura, Yasutaka Kuzumoto, Woogun Kang, Shigeru Aomori, Yasuhiko Arakawa

  Bottom-contact pentacene thin-film transistors (TFTs) with different electrode types have been fabricated to investigate influence of the adhesion layers and surface modification on the transistor characteristics. Gold-nickel alloy or Ti was used for the adhesion layer; the drain/source electrodes were modified with pentafluorobenzenethiol (PFBT) or nonmodified. The TFTs with AuNi layers and PFBT-modified electrodes exhibit channel-length independent saturation mobility. The electrode-type TFT with a channel length of 2.2 mu m has a saturation mobility of 0.73 cm(2)/V s and a transconductance of 229 mu S/mm. The high performance is attributed to the low contact resistance of 408 cm. (C) 2010 American Institute of Physics. [doi:10.1063/1.3465735]

  AMER INST PHYSICS, Jul. 2010, APPLIED PHYSICS LETTERS, 97(3) (3), 33306, English

  [Refereed]

  Scientific journal


• Esaki diodes live and learn

  Leo Esaki, Masatoshi Kitamura, Satoshi Iwamoto, Yasuhiko Arakawa

  We report, as the result of shelf-life tests for Esaki diodes, the observation of minute but tangible reductions in the tunnel current after the lapse of half a century. The reduction could be attributed to 0.25% widening in the tunnel path.

  JAPAN ACAD, Apr. 2010, PROCEEDINGS OF THE JAPAN ACADEMY SERIES B-PHYSICAL AND BIOLOGICAL SCIENCES, 86(4) (4), 451 - 453, English, Domestic magazine

  [Refereed]

  Scientific journal


• Esaki diode is still a radio star, half a century on

  Leo Esaki, Yasuhiko Arakawa, Masatoshi Kitamura

  NATURE PUBLISHING GROUP, Mar. 2010, NATURE, 464(7285) (7285), 31 - 31, English, International magazine

  [Refereed]


• Complementary use of organic and oxide semiconductors

  Jong H. Na, Masatoshi Kitamura, Yasuhiko Arakawa

  Complementary use of p-type organic and n-type oxide semiconductors is presented. First, we demonstrated complementary circuits using low-voltage operating high performance pentacene and amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs). The field-effect mobilities of the pentacene and a-IGZO transistors are 0.6 and 17.1 cm(2)/V s, respectively at an operating voltage of 10 V. A complementary inverter composed of these transistors exhibits good voltage transfer characteristics with a high gain of similar to 56. A five-stage ring oscillator with the inverters yields an output frequency of 200 Hz at 10 V, corresponding to a propagation delay of 1 ms. Second, together with the electrical device, we demonstrated an optoelectronic device, light-emitting diodes (LEDs), using organic/oxide hybrid junctions. The hybrid p-n junction LEDs are composed of N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (alpha-NPD) and sputtered ZnO. Similar with conventional p-n junction diodes, the hybrid junction shows a good current rectification and electroluminescence (EL) under forward bias. We found that the EL bands from the device agree well with the photoluminescence peaks from alpha-NPD and ZnO, implying the radiative recombination of injected charges occurs in both components of the junction.

  SPIE-INT SOC OPTICAL ENGINEERING, 2010, OXIDE-BASED MATERIALS AND DEVICES, 7603, English

  [Refereed]

  International conference proceedings


• Hybrid p-n junction light-emitting diodes based on sputtered ZnO and organic semiconductors

  Jong H. Na, M. Kitamura, M. Arita, Y. Arakawa

  AIP Publishing, Dec. 2009, Applied Physics Letters, 95(25) (25), 253303 - 253303

  [Refereed]

  Scientific journal


• Current-gain cutoff frequencies above 10 MHz for organic thin-film transistors with high mobility and low parasitic capacitance

  Masatoshi Kitamura, Yasuhiko Arakawa

  The current-gain cutoff frequency for bottom contact n-channel C(60) thin-film transistors (TFTs) with channel lengths of 2-10 mu m has been investigated. Patterned gate electrodes were adopted to reduce parasitic capacitance of the TFTs. The cutoff frequency was estimated by direct measurement of the gate and drain modulation currents. The estimated cutoff frequency increases consistently with reducing channel length. A maximum cutoff frequency of 20.0 MHz was obtained from a C(60) TFT with a channel length of 2 mu m and a saturation mobility of 1.11 cm(2)/V s.

  AMER INST PHYSICS, Jul. 2009, APPLIED PHYSICS LETTERS, 95(2) (2), English

  [Refereed]

  Scientific journal


• Dual luminescence from organic/inorganic hybrid p-n junction light-emitting diodes

  Jong H. Na, M. Kitamura, M. Arita, Y. Arakawa

  We fabricated a hybrid p-n junction structure using n-type InGaN/GaN multiple quantum wells (MQWs) and p-type N,N-'-diphenyl-N,N-'-bis(1-naphthyl)-1,1(')-biphenyl-4,4(')-diamine (alpha-NPD). The hybrid structure shows a good current rectifying characteristic similar with conventional p-n junction diodes. Electroluminescence (EL) of the hybrid device exhibits two emission bands originated from InGaN/GaN MQWs, as well as alpha-NPD layer. The EL properties can be explained by either (or both) electron-hole charge transport between the components or (and) efficient energy transfer via Foster mechanism. The device characteristics could be applicable to various multicolor light-emitting diodes by constructing other organic/inorganic hybrid junctions.

  AMER INST PHYSICS, May 2009, APPLIED PHYSICS LETTERS, 94(21) (21), English

  [Refereed]

  Scientific journal


• Threshold voltage control of bottom-contact n-channel organic thin-film transistors using modified drain/source electrodes

  Masatoshi Kitamura, Yasutaka Kuzumoto, Shigeru Aomori, Masakazu Kamura, Jong Ho Na, Yasuhiko Arakawa

  Bottom-contact n-channel C(60) thin-film transistors (TFTs) with drain/source electrodes modified by benzenethiol derivatives have been fabricated to investigate the influence of the modification on the transistor characteristics. Modification using methylbenzenethiol, aminobenzenethiol, and (dimethylamino)benzenethiol having electron-donating groups causes threshold voltages to shift to low voltages. In addition, the modification provides no significant decrease in saturation mobilities. A C(60) TFT with (dimethylamino)benzenethiol-modified electrodes has a low threshold voltage of 5.1 V as compared to that of 16.8 V for a TFT with nonmodified electrodes. The threshold-voltage shift is probably because the modification reduces electron-injection barrier height and improves electron injection into organic semiconductors.

  AMER INST PHYSICS, Feb. 2009, APPLIED PHYSICS LETTERS, 94(8) (8), English

  [Refereed]

  Scientific journal


• Low-voltage-operating organic complementary circuits based on pentacene and C-60 transistors

  Jong H. Na, Masatoshi Kitamura, Yasuhiko Arakawa

  Low-voltage-operating organic complementary inverters and ring oscillators were fabricated using high field effect mobility pentacene and C-60 thin-film transistors (TFTs). The mobilities of pentacene and C-60 TFTs were 0.44 and 0.61 cm(2)/V s, respectively. The complementary inverters composed of these TFTs operated in the voltage range of 2-10 V with large gain values up to 65. The inverter yields 5-stage ring oscillators with a high oscillation frequency of 80 Hz at 10 V. (C) 2008 Elsevier B.V. All rights reserved.

  ELSEVIER SCIENCE SA, Jan. 2009, THIN SOLID FILMS, 517(6) (6), 2079 - 2082, English

  [Refereed]

  Scientific journal


• Organic/inorganic hybrid complementary circuits based on pentacene and amorphous indium gallium zinc oxide transistors

  Jong H. Na, M. Kitamura, Y. Arakawa

  Complementary inverters composed of pentacene for the p-channel thin-film transistors (TFTs) and amorphous indium gallium zinc oxide for the n-channel TFTs have been fabricated on glass substrates. The p- and n-channel TFTs have field-effect mobilities of 0.6 and 17.1 cm(2)/V s, respectively, and inverters yield a high gain of similar to 56. Complementary five-stage ring oscillator exhibits a good dynamic operation with an output frequency of 200 Hz at 10 V. Since both channel layers are stable in air and can be formed by room temperature deposition process, the hybrid circuits are applicable to flexible electronic devices.

  AMER INST PHYSICS, Nov. 2008, APPLIED PHYSICS LETTERS, 93(21) (21), English

  [Refereed]

  Scientific journal


• High field-effect mobility amorphous InGaZnO transistors with aluminum electrodes

  Jong H. Na, M. Kitamura, Y. Arakawa

  We report on the device characteristics of amorphous indium gallium zinc oxide thin-film transistors (TFTs) with aluminum (Al) electrodes. The TFTs exhibited a high performance with a field-effect mobility of 11.39 cm(2)/V s, a subthreshold swing of 181 mV/ decade, and an on-off ratio of 10(7). Further improvement in device performance was achieved by doping the source/drain contact regions, resulting in an enhanced mobility of 16.6 cm(2)/V s at an operating voltage as low as 5 V. (C) 2008 American Institute of Physics.

  AMER INST PHYSICS, Aug. 2008, APPLIED PHYSICS LETTERS, 93(6) (6), English

  [Refereed]

  Scientific journal


• Bottom-contact fullerene C(60) thin-film transistors with high field-effect mobilities

  Masatoshi Kitamura, Shigeru Aomori, Jong Ho Na, Yasuhiko Arakawa

  Fullerene C(60) thin-film transistors (TFTs) with bottom-contact structure have been fabricated. The parasitic resistance was extracted using gated-transmission line method. The drain/source electrodes consisted of a single Au layer with no adhesion layer; the channel lengths ranged from 5 to 40 mu m. The field-effect mobilities in the saturation regime slightly depended on the channel length, ranging from 2.45 to 3.23 cm(2)/V s. The mobility of 3.23 cm(2)/V s was obtained from the TFT with a channel length of 5 mu m and is the highest in organic TFTs with bottom-contact structure. The high mobility is due to the low parasitic resistance. (C) 2008 American Institute of Physics.

  AMER INST PHYSICS, Jul. 2008, APPLIED PHYSICS LETTERS, 93(3) (3), 33313, English

  [Refereed]

  Scientific journal


• Pentacene-based organic field-effect transistors

  Masatoshi Kitamura, Yasuhiko Arakawa

  Organic field-effect transistors (FETs) have attracted considerable attention because of their potential for realizing large-area, mechanically flexible, lightweight and low-cost devices. Pentacene, which is a promising material for organic FETs, has been intensely studied. This article reviews the basic properties of pentacene films and crystals, and the characteristics of pentacene FETs fabricated under various conditions, including our recent achievement of low-voltage operating high-mobility FETs. The basic properties include the crystal polymorph, the band structure and the effective mass. These data have been used for discussion of carrier transport and mobility in pentacene films. The characteristics of pentacene FETs generally depend on the conditions of the pentacene film and the gate-dielectric surface. The dependences are summarized in the article. In addition, liquid-crystal displays and organic light-emitting device arrays using pentacene FETs are reviewed as applications of organic FETs, and complementary metal-oxide-semiconductor circuits using our low-voltage operating FETs are also shown.

  IOP PUBLISHING LTD, May 2008, JOURNAL OF PHYSICS-CONDENSED MATTER, 20(18) (18), 1 - 16, English

  [Refereed]


• Complementary two-input NAND gates with low-voltage-operating organic transistors on plastic substrates

  Jong Ho Na, Masatoshi Kitamura, Yasuhiko Arakawa

  We fabricated two-input NAND gates composed of p-channel pentacene and n-channel C-60 transistors. The logic devices were prepared on flexible polymer substrates through a shadow mask process. Correct NAND logic functionality was demonstrated at a wide voltage range of 2 - 7V. From voltage transfer characteristics of the NAND gates, we obtained impressive signal gains up to 120 and large noise margins in the given voltage range. (c) 2008 The Japan Society of Applied Physics.

  IOP PUBLISHING LTD, Feb. 2008, APPLIED PHYSICS EXPRESS, 1(2) (2), English

  [Refereed]

  Scientific journal


• Low-voltage operating CMOS circuits with high field-effect mobility organic transistors

  Masatoshi Kitamura, Jong Ho Na, Yasuhiko Arakawa

  Low-voltage operating organic CMOS circuits are reviewed in the manuscript. The CMOS circuits consist of p-channel pentacene and n-channel C60 thin-film transistors, which have mobilities of 0.2 to 1.1 cm2/Vs and operate at 1 to 7 V. Fabricated CMOS inverters, NAND and ring oscillators operated at voltages of 2 to 5 V at least.

  2008, IDW '08 - Proceedings of the 15th International Display Workshops, 2, 1507 - 1510, English

  International conference proceedings


• Two-dimensional photonic crystal resist membrane nanocavity embedding colloidal dot-in-a-rod nanocrystals

  Luigi Martiradonna, Luigi Carbone, Aniwat Tandaechanurat, Masatoshi Kitamura, Satoshi Iwamoto, Liberato Manna, Massimo De Vittorio, Roberto Cingolani, Yasuhiko Arakawa

  A novel technique for the fabrication of photonic crystal (PC) nanocavities coupled with colloidal nanocrystals is presented. A waveguiding resist membrane embedding highly emitting dot-in-a-rod nanocrystals was patterned through e-beam lithography and released through wet etching process. The proposed approach makes the PC structure independent of fabrication imperfections induced by etching steps. Micro-photoluminescence spectra revealed degenerated resonant modes (Q-factor similar to 700) whose fabrication-induced spectral splitting is comparable to the full width at half-maximum of the peaks. Active nanocavities tunable from visible to infrared spectral range on GaAs or Si substrates can be easily implemented by this technique.

  AMER CHEMICAL SOC, Jan. 2008, NANO LETTERS, 8(1) (1), 260 - 264, English, International magazine

  [Refereed]

  Scientific journal


• Low-voltage-operating fullerene C-60 thin-film transistors with various surface treatments

  Masatoshi Kitamura, Yasutaka Kuzumoto, Masakazu Kamura, Shigeru Aomori, Jong Ho Na, Yasuhiko Arakawa

  Influence of surgace treatment on fullerne C-60 thin-film transistors (TFTs) has been investingated. Phenyltrimethoxysilane (PTS), Hexamethldisilazane (HMDS) and octadecytrimethoxysilane (ODS) were used for the surface treatment. The treated surface was investigated by water-contact-angle measurement and the C-60 deposited on the surface was observed with scanning electron microscope. As a result, C-60 TFT with the ODS-treated insulator exhibited the highest field-effect mobility of 1.46 cm(2)/Vs. In addition, the TFTs operated at a low voltage of 5 V by adopting high-dielectric-constant gate insulator. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  WILEY-V C H VERLAG GMBH, 2008, PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 5, NO 9, 5(9) (9), 3181 - +, English

  [Refereed]

  International conference proceedings


• High performance n-channel thin-film transistors with an amorphous phase C-60 film on plastic substrate

  Jong H. Na, M. Kitamura, Y. Arakawa

  We fabricated high mobility, low voltage n-channel transistors on plastic substrates by combining an amorphous phase C-60 film and a high dielectric constant gate insulator titanium silicon oxide (TiSiO2). The transistors exhibited high performance with a threshold voltage of 1.13 V, an inverse subthreshold swing of 252 mV/decade, and a field-effect mobility up to 1 cm(2)/V s at an operating voltage as low as 5 V. The amorphous phase C-60 films can be formed at room temperature, implying that this transistor is suitable for corresponding n-channel transistors in flexible organic logic devices.

  AMER INST PHYSICS, Nov. 2007, APPLIED PHYSICS LETTERS, 91(19) (19), English

  [Refereed]

  Scientific journal


• High-performance fullerene C-60 thin-film transistors operating at low voltages

  Masatoshi Kitamura, Yasutaka Kuzumoto, Masakazu Kamura, Shigeru Aomori, Yasuhiko Arakawa

  Low-voltage operation of fullerene C-60 thin-film transistors (TFTs) has been realized using zirconium-silicon oxide (ZSO) as a gate insulator. The gate insulator consisted of triple layers of SiO2/ZSO/SiO2 deposited by rf sputtering. The C-60 TFTs with the insulators operated at a low voltage of 5 V. The surface of the insulator was treated with hexamethyldisilazane (HMDS) or octadecyltrimethoxysilane (ODS). The C-60 TFT with the ODS-treated insulator exhibited higher performance than that with the HMDS-treated insulator, and it had a field-effect mobility of 1.46 cm(2)/V s, threshold voltage of 1.9 V, and a current on/off ratio of 2x10(6). (C) 2007 American Institute of Physics.

  AMER INST PHYSICS, Oct. 2007, APPLIED PHYSICS LETTERS, 91(18) (18), English

  [Refereed]

  Scientific journal


• Low-voltage-operating complementary inverters with C-60 and pentacene transistors on glass substrates

  Masatoshi Kitamura, Yasuhiko Arakawa

  Organic complementary inverters with C-60 and pentacene thin-film transistors (TFTs) have been fabricated on glass substrate. The inverter operated at low voltages of 1-5 V. The C-60 and pentacene TFTs had high field-effect mobilities of 0.68 and 0.59 cm(2)/V s, and threshold voltage of 0.80 and -0.84 V, respectively. The low threshold voltage enables the low voltage operation of the inverter. (C) 2007 American Institute of Physics.

  AMER INST PHYSICS, Jul. 2007, APPLIED PHYSICS LETTERS, 91(5) (5), English

  [Refereed]

  Scientific journal


• High performance flexible pentacene thin-film transistors fabricated on titanium silicon oxide gate dielectrics

  Jong H. Na, M. Kitamura, D. Lee, Y. Arakawa

  Pentacene thin-film transistors (TFTs) with a high dielectric constant gate insulator, titanium silicon oxide (TiSiO2), were fabricated on flexible polyethylene naphthalate films coated with indium tin oxide layers. In order to define the device characteristics, the thickness dependence of the gate dielectric properties was studied. The pentacene TFT with a 132-nm-thick TiSiO2 film showed high performance with a threshold voltage of -0.88 V, an inverse subthreshold slope of 317 mV/decade. From the current-voltage characteristics, the field-effect mobility was obtained, resulting in an impressive mobility of 0.67 cm(2)/V s at an operating voltage as low as -5 V. (C) 2007 American Institute of Physics.

  AMER INST PHYSICS, Apr. 2007, APPLIED PHYSICS LETTERS, 90(16) (16), English

  [Refereed]

  Scientific journal


• Fabrication and optical characterization of III-nitride air-bridge photonic crystal with GaN quantum dots

  Ning Li, M. Arita, S. Kako, M. Kitamura, S. Iwamoto, Y. Arakawa

  We report the fabrication of Ill-nitride air-bridge photonic crystals with GaN quantum dots for the first time. Photonic crystals with various periodicities and airhole diameters were fabricated. Abrupt vertical profiles and high aspect ratio (similar to 3) were achieved with excellent reproducibility even to the structure with periodicity as small as 150 run. The fabrication of air-bridge structure utilizing photoelectrochernical etching of SiC was demonstrated. Strong photoluminescence enhancement by a factor of 5 was observed from GaN QDs embedded in the air-bridge PC layer. This is due to the coupling of PL light with photonic bands above the light cone, thus results in the enhanced light extraction efficiency. These results will lead to the realization of high efficiency quantum dots based emitting devices in blue and ultraviolet range. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  WILEY-V C H VERLAG GMBH, 2007, PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 4, NO 1, 4(1) (1), 90 - +, English

  [Refereed]

  International conference proceedings


• Flexible organic LEDs with parylene thin films for biological implants

  Tomohiro Yamamura, Masatoshi Kitamura, Kaori Kuribayashi

  This paper describes an ultra thin, flexible device with organic light emitting diodes (OLEDs) between Parylene thin films (20 mu m or less in total thickness). The device was formed on a glass substrate and could be easily peeled off without breaking. The OLEDs in the flexible device emitted light with high brightness, and were useful as excitation light sources for fluorescent dyes. We have also demonstrated a flexible probe with an OLED for the application of biological implants toward in vivo fluorescent imaging and optical stimulation of cells.

  IEEE, 2007, PROCEEDINGS OF THE IEEE TWENTIETH ANNUAL INTERNATIONAL CONFERENCE ON MICRO ELECTRO MECHANICAL SYSTEMS, VOLS 1 AND 2, 674 - +, English

  [Refereed]

  International conference proceedings


• Organic Light-Emitting Devices Using Photonic Crystals

  北村 雅季, 岩本 敏, 荒川 泰彦

  Lead, Nov. 2006, レーザー研究, 34(11) (11), 767 - 772, Japanese

  [Refereed]

  Scientific journal


• High-performance pentacene thin-film transistors with high dielectric constant gate insulators

  M. Kitamura, Y. Arakawa

  Pentacene thin-film transistors (TFTs) with titanium silicon oxide (Ti1-xSixO2) gate insulator have been fabricated to realize high field-effect mobility at practical voltages. The Ti1-xSixO2 films deposited by rf sputtering exhibited a flat surface and high dielectric constant. The pentacene TFT with the Ti1-xSixO2 gate insulator had high performance with a threshold voltage of -1.6 V, an inverse subthreshold slope of 0.13 V/decade, and a current on/off ratio of 10(7) at a voltage of -10 V. The field-effect mobilities of higher than 1 cm(2)/V s were obtained in the whole voltage range of -2 to -15 V.

  AMER INST PHYSICS, Nov. 2006, APPLIED PHYSICS LETTERS, 89(22) (22), English

  Scientific journal


• Resonant-wavelength control in visible-light range of organic photonic crystal nanocavities

  Masatoshi Kitamura, Satoshi Iwamoto, Yasuhiko Arakawa

  Organic-based photonic crystal (PC) nanocavities emitting in the visible-light range have been demonstrated. Three types of organic layer were used as emitting layers for PCs with emission spectra in the blue, green and red light wavelength ranges. Emission peaks caused by the resonant modes of the PC nanocavities were observed. The wavelength of the peak was controlled by changing the lattice constant of the PC. The emission peaks were observed in the wavelength range of 435 to 747 nm.

  INST PURE APPLIED PHYSICS, Aug. 2006, JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS, 45(8A) (8A), 6112 - 6115, English

  [Refereed]

  Scientific journal


• Synthesis of Alq(3)-pendent soluble polymers and their application to organic light emitting diode

  Toshio Takayama, Masatoshi Kitamura, Yasushi Kobayashi, Yasuhiko Arakawa, Kazuaki Kudo

  Soluble polymethacrylates having pendent tris(8-hydroxyquinolinato) aluminum (Alq(3)) moieties were synthesized and applied to organic light emitting diode (OLED). 8-Hydroxyquinolines (8-HQs) having secondary alkyl groups at 7-position were employed as ligands as it is expected that these alkyl groups prevent external molecules from accessing to the metal center of the complexes leading to suppression of ligand-exchange-induced crosslinking and insolubilization. The ligands were synthesized from 7-methoxycarbonyl-8-hydroxyquinoline via alkylation with Grignard reagents and subsequent reductive dehydroxylation. These ligands were then derivatized to polymeric ligands through chloromethylation at 5-position, introduction of (methacryloyloxy) ethoxy moiety by Williamson ether synthesis, and radical polymerization. Complex formation with aluminum cation was carried out for various combinations of low-molecular-weight and polymer ligands. Some of the polymers obtained were soluble in organic solvents. Two-layer-type OLED devices were then prepared from the soluble Alq(3)-pendent polymers and poly (vinyl carbazole). Alq3-pendent polymers having 8-HQs with smaller 7-alkyl groups gave devices with better light-emitting efficiency compared to those with larger 7-alkyl groups.

  SOC POLYMER SCIENCE JAPAN, 2006, KOBUNSHI RONBUNSHU, 63(10) (10), 696 - 703, Japanese

  [Refereed]

  Scientific journal


• Conformation and Local Environment Dependent Conductance of DNA Molecules

  M. S. Xu, R. G. Endres, S. Tsukamoto, M. Kitamura, S. Ishida, Y. Arakawa

  Wiley, Dec. 2005, Small, 1(12) (12), 1168 - 1172, English

  [Refereed]

  Scientific journal


• Enhanced light emission from an organic photonic crystal with a nanocavity

  M Kitamura, S Iwamoto, Y Arakawa

  An organic photonic crystal (PC) with a nanocavity has been fabricated on a SiO2 membrane with air holes. The emission peak caused by the resonant mode of the nanocavity was clearly observed from the nanocavity area of the PC. The emission peak corresponded to degenerated dipole modes from comparison between measured and calculated results. Modification of a nanocavity caused the peak splitting of dipole modes and the appearance of a peak corresponding to a hexapole mode. The emission peak with a quality factor of about 1000 was obtained from a PC with a modified nanocavity. (C) 2005 American Institute of Physics.

  AMER INST PHYSICS, Oct. 2005, APPLIED PHYSICS LETTERS, 87(15) (15), English

  Scientific journal


• Conductance of single thiolated poly(GC)-poly(GC) DNA molecules

  M. S. Xu, S. Tsukamoto, S. Ishida, M. Kitamura, Y. Arakawa, R. G. Endres, M. Shimoda

  AIP Publishing, Aug. 2005, Applied Physics Letters, 87(8) (8), 083902 - 083902, English

  [Refereed]

  Scientific journal


• Enhanced luminance efficiency of organic light-emitting diodes with two-dimensional photonic crystals

  M Kitamura, S Iwamoto, Y Arakawa

  Organic light-emitting diodes (OLEDs) with two-dimensional photonic crystal were fabricated to improve their light-extraction efficiency. The electroluminescence (EL) spectra from these OLEDs depended on the lattice constant of the photonic crystal. The relationship between the EL spectra and the lattice constant was investigated. On the basis of this investigation, a lattice constant was optimized to obtain a large improvement in luminance. In addition, OLEDs doped with coumarin 6 provided a larger improvement in luminance than nondoped OLEDs. The coumarin 6 doped OLED with the optimized lattice constant provided improvements of 62% in luminance in the normal direction and 25% in spatially integrated EL intensity.

  JAPAN SOC APPLIED PHYSICS, Apr. 2005, JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS, 44(4B) (4B), 2844 - 2848, English

  Scientific journal


• Enhanced light emission of an organic semiconductor based two-dimensional photonic crystal with a nanocavity

  M Kitamura, S Iwamoto, Y Arakawa

  Organic based two-dimensional photonic crystals with a nanocavitiy have fabricated. Emission peak at the resonant wavelength was clearly observed. Adjusting the cavity structure, we obtained more than ten times enhanced intensity at the resonant wavelength.

  IEEE, 2005, 2005 PACIFIC RIM CONFERENCE ON LASERS AND ELECTRO-OPTICS, 678 - 679, English

  [Refereed]

  International conference proceedings


• Organic semiconductor based two-dimensional photonic crystal with a single defect

  M Kitamura, S Iwamoto, Y Arakawa

  A two-dimensional organic photonic crystal with a single defect was fabricated on silicon dioxide membranes. Light emission from the single defect in the organic photonic crystal was observed for the first time. (c) 2005 Optical Society of America.

  OPTICAL SOC AMERICA, 2005, 2005 Conference on Lasers & Electro-Optics (CLEO), Vols 1-3, 547 - 549, English

  [Refereed]

  International conference proceedings


• Soluble polymer complexes having AlQ3-type pendent groups

  Toshio Takayama, Masatoshi Kitamura, Yasushi Kobayashi, Yasuhiko Arakawa, Kazuaki Kudo

  Polymethacrylate having a pendent 8-hydroxyquinoline moiety was prepared using Kelex-100 (7-(4-ethyl-1-methyloctyl)-8-hydroxyquinoline) as a starting material. A soluble polymer having tris(8-hydroxyquinolinato)aluminum (AlQ 3)-type side chains was obtained through the complexation of the polymer with Me3Al in the presence of a monomeric Kelex-100. The polymer complex was applied to an organic light-emitting diode (OLED) device through a spin-cast process.

  Jun. 2004, Macromolecular Rapid Communications, 25(12) (12), 1171 - 1174, English

  [Refereed]

  Scientific journal


• Time-of-flight measurement of lateral carrier mobility in organic thin films

  M Kitamura, T Imada, S Kako, Y Arakawa

  Lateral carrier transport in a copper phthalocyanine (CuPc) thin film has been investigated by the time-of-flight technique using a micro-excitation system. Drift mobility in the CuPc film has been estimated from the transient photocurrent measured for various electric field strengths. The drift mobility has been compared to the field-effect mobility of a thin-film transistor with CuPc as the channel material. The field-effect mobility was comparable to the drift mobility measured by the TOF technique.

  INST PURE APPLIED PHYSICS, Apr. 2004, JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, 43(4B) (4B), 2326 - 2329, English

  [Refereed]

  Scientific journal


• Organic light-emitting diodes driven by pentacene-based thin-film transistors

  M Kitamura, T Imada, Y Arakawa

  Integrated circuits with an organic light-emitting diode (OLED) and a thin-film transistor (TFT) based on small molecules were fabricated on a glass substrate. The field-effect mobility and the current on/off ratio of the integrated TFTs with a pentacene layer deposited at room temperature were 0.12 cm(2)/V s and higher than 10(3), respectively. The OLEDs had a multilayer structure containing tris-(8-hydroxyquinoline) aluminum doped with coumarin 6 to obtain high luminance efficiency. The luminance was controlled in the range of up to approximately 1000 by applying the gate voltage of 10 to -10 V. The value of the luminance is sufficient for conventional displays. (C) 2003 American Institute of Physics.

  AMER INST PHYSICS, Oct. 2003, APPLIED PHYSICS LETTERS, 83(16) (16), 3410 - 3412, English

  [Refereed]

  Scientific journal


• Organic transistor circuits for application to organic light-emitting-diode displays

  M Kitamura, T Imada, Y Arakawa

  Organic thin-film transistor circuits based on the small molecule, copper phthalocyanine, have been demonstrated for application to an active-matrix display with organic light-emitting diodes. The circuit consists of two organic thin-film transistors and one storage capacitor which provide continuous current under pulsed operation. The transistors for the circuit have been designed on the basis of the current characteristics of the individual transistors. Continuous output current has been obtained under pulsed voltage operation by using the organic transistor circuit.

  INST PURE APPLIED PHYSICS, Apr. 2003, JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, 42(4B) (4B), 2483 - 2487, English

  [Refereed]

  Scientific journal


• Squeezed states of light in a cavity with a local two-photon absorber

  M Kitamura, T Tokihiro

  Squeezed states of light are theoretically investigated in a system with a locally placed two-photon absorption medium. We assume that the two-photon absorption process is caused by elementary excitations in the medium (such as biexcitons). Many eigenmodes of photons and those of the elementary excitations are taken into account because of the locality of the absorber. Multi-mode Wigner functions are defined and used for representation of the density operator of the electromagnetic field. The Wigner functions exhibit multi-variable Gaussian distribution and the quantum states of photons are multi-mode quadrature squeezed states. We also discuss effects on squeezing due to detuning of the incident light, the size of the medium, the position of a photo-detector, and damping rates of photons and the elementary excitations.

  IOP PUBLISHING LTD, Oct. 1999, JOURNAL OF OPTICS B-QUANTUM AND SEMICLASSICAL OPTICS, 1(5) (5), 546 - 556, English

  Scientific journal


• Direct observation of the transition from a 2D layer to 3D islands at the initial stage of InGaAs growth on GaAs by AFM

  M Kitamura, M Nishioka, R Schur, Y Arakawa

  We have studied the transition from two-dimensional (2D) growth to three-dimensional (3D) growth at the initial stage of In0.8Ga0.2As growth with the Stranski-Krastanov mode on GaAs by metal organic chemical vapor phase epitaxy. The surface morphology was observed by atomic force microscopy. In the early stage of the growth, the formation of 2D islands and that of holes were alternately repeated. 3D islands (quantum dots) appeared after the deposition of 3 monolayers. 2D islands with 4 monolayer thickness of In0.8Ga0.2As were also formed at the same time. The 2D islands shunned the quantum dots and grew laterally. In addition, we obtained a photoluminescence spectrum with several peaks corresponding to higher subbands with a high excitation intensity from the quantum dots.

  ELSEVIER SCIENCE BV, Jan. 1997, JOURNAL OF CRYSTAL GROWTH, 170(1-4) (1-4), 563 - 567, English

  [Refereed]

  Scientific journal


• Growth and optical properties of self-assembled quantum dots for semiconductor lasers with confined electrons and photons

  Y Arakawa, M Nishioka, H Nakayama, M Kitamura

  We discuss fabrication of InGaAs quantum dot structures using the self-assembling growth technique with the Stranski-Krastanow growth mode in MOCVD, including optical properties of the nano-structures. The formation process of the quantum dot islands was clarified by observing the samples grown under various conditions with an atomic force microscope. A trial for self-alignment of the quantum dots was also investigated. On the basis of these results; as the first step toward the ultimate semiconductor lasers in which both electrons and photons are fully quantized, a vertical microcavity InGaAs/GaAs quantum dot laser was demonstrated. Finally a perspective of the quantum dot lasers is discussed, including the bottleneck issues and the impact of the quantum dot structures for reducing threshold current in wide bandgap lasers such as GaN lasers.

  IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG, Nov. 1996, IEICE TRANSACTIONS ON ELECTRONICS, E79C(11) (11), 1487 - 1494, English

  [Refereed]

  Scientific journal


• Light emission from vertical-microcavity quantum dot laser structures

  M Nishioka, R Schur, M Kitamura, H Watabe, Y Arakawa

  A vertical microcavity laser structure with an active layer of Stranski-Krastanow quantum dots was fabricated for the first time. The microcavity consists of an InGaAs quantum dot layer grown by MOCVD, located between two AlAs/Al0.2Ga0.8As distributed Bragg-reflector mirrors. The length of the microcavity was 4 lambda(lambda = 884 nm). The cavity effect was evidenced by the difference of the PL linewidths of samples with and without the cavity.

  ELSEVIER SCIENCE BV, Sep. 1996, PHYSICA B, 227(1-4) (1-4), 404 - 406, English

  [Refereed]

  Scientific journal


• Fabrication and optical properties of self assembled InGaAs quantum dots embedded in microcavities

  R Schur, M Nishioka, M Kitamura, H Watabe, Y Arakawa

  I E E E, 1996, 1996 EIGHTH INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE AND RELATED MATERIALS, 750 - 752, English

  [Refereed]

  International conference proceedings


• Epitaxial Growth Controlled in Three Dimensions. Self-Assembling of Quantum Boxes using Stranski-Krastanov Growth Mode.

  Yasuhiko ARAKAWA, Masato KITAMURA

  これまで行われてきた量子ドット構造の作製技術の研究の中で,特に薄膜の成長様式のひとつであるStranski-Krastanov(SK)成長モードによる自然形成技術に焦点を合わせて論じる。 まず量子ドット作製技術が満たすべき一般的要件およびStranski-Krastanov成長モードを用いた量子ドット作製の研究の流れについて概観する。これらをふまえ筆者らの成果を中心に論じている。成長温度,成長時間および使用する基板を変えたときのドットの形成の様子を明らかにし,ある成長時間以上で急激にドットの密度が高くなることを示した。また,ドットの形成は基板にも敏感で傾斜基板を使用すると同じ成長時間でもJust基板に比べてドットの密度が高いことを示した。さらにドットの形成について詳しく調べるためにAFMにより表面構造を観察した。マルチステップを形成することによりドットがステップ端に形成されやすいことを確かめた。また,この特徴を利用してステップに沿ってドットを配列することに成功した。

  Surface Science Society Japan, Oct. 1995, Hyomen Kagaku, 16(10) (10), 624 - 630, Japanese

  [Refereed]

  Scientific journal


• FORMATION OF INGAAS QUANTUM DOTS ON GAAS MULTI-ATOMIC STEPS BY METALORGANIC CHEMICAL-VAPOR-DEPOSITION GROWTH

  M KITAMURA, M NISHIOKA, J OSHINOWO, Y ARAKAWA

  Aligned InGaAs quantum dots as small as 20 nm were naturally formed at multi-atomic step edges by metalorganic chemical vapor deposition growth. In addition, it was found that anisotropic structure of InGaAs along the step edges toward the [110]A direction appears with the increase of growth time of InGaAs. This phenomenon may be useful in the formation of quantum wires.

  JAPAN J APPLIED PHYSICS, Aug. 1995, JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, 34(8B) (8B), 4376 - 4379, English

  [Refereed]

  Scientific journal


• IN-SITU FABRICATION OF SELF-ALIGNED INGAAS QUANTUM DOTS ON GAAS MULTIATOMIC STEPS BY METALORGANIC CHEMICAL-VAPOR-DEPOSITION

  M KITAMURA, M NISHIOKA, J OSHINOWO, Y ARAKAWA

  AMER INST PHYSICS, Jun. 1995, APPLIED PHYSICS LETTERS, 66(26) (26), 3663 - 3665, English

  [Refereed]

  Scientific journal


• Spontaneous formation of aligned InGaAs quantum dots on GaAs multi-atomic steps by metalorganic chemical vapor deposition growth

  M KITAMURA, M NISHIOKA, J OSHINOWO, Y ARAKAWA

  I E E E, 1995, SEVENTH INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE AND RELATED MATERIALS, CONFERENCE PROCEEDINGS, 763 - 765, English

  [Refereed]

  International conference proceedings

• Flexible and Printed Electronics

  Lead, IOP Publishing, 01 Jun. 2022, Japanese Journal of Applied Physics, 61(SE) (SE), SE0001 - SE0001, English

  [Invited]

  Introduction scientific journal


• Flexible and Printed Electronics

  Lead, IOP Publishing, 01 May 2017, Japanese Journal of Applied Physics, 56(5S2) (5S2), 05E001 - 05E001, English

  [Invited]


• Recent Advances in Molecular Electronics and Bio-electronics

  Lead, IOP Publishing, 01 Mar. 2016, Japanese Journal of Applied Physics, 55(3S2) (3S2), 03D001 - 03D001


• C-9-2 Research Progress of Organic Thin-Film Transistors and Prospects of Commercial Products

  Kitamura Masatoshi

  The Institute of Electronics, Information and Communication Engineers, 24 Feb. 2015, Proceedings of the IEICE General Conference, 2015(2) (2), 38 - 38, Japanese


• Large conductance C_<60> thin-film transistors

  KITAMURA Masatoshi, NA Jong Ho, ARAKAWA Yasuhiko

  Bottom-contact C_<60> thin-film transistors (TFTs) have been fabricated. The channel lengths (L) ranged from 5 to 40μm. The saturation mobilities slightly depended on the channel length, ranging from 2.45 to 3.23cm^2/Vs. The highest mobility of 3.23cm^2/Vs was obtained from a TFT with L=5μm. The TFT had a conductance of 119μS/mm; which is relative high as compared to conventional organic TFTs. To investigate the reason that the short channel TFTs has high mobilities, we examined parasitic resistance. The calculated parasitic resistance was less than 1kWcm. The low parasitic resistance causes high mobility of the TFTs with with L=5μm.

  The Institute of Electronics, Information and Communication Engineers, 24 Oct. 2008, IEICE technical report, 108(272) (272), 9 - 14, Japanese


• 有機トランジスタの低電圧動作・高性能化とCMOS応用

  北村 雅季, 荒川 泰彦

  30 May 2008, Molecular electronics and bioelectronics, 19(2) (2), 65 - 68, Japanese


• 低電圧動作有機CMOS回路--フレキシブルディスプレイへの応用を目指して

  北村 雅季, 荒川 泰彦

  日本工業出版, Jan. 2008, 画像ラボ, 19(1) (1), 9 - 12, Japanese


• 有機薄膜トランジスタの低電圧動作と閾値電圧

  北村 雅季, 荒川 泰彦

  26 Nov. 2007, Molecular electronics and bioelectronics, 18(4) (4), 297 - 302, Japanese


• High field-effect-mobility organic thin-film transistors using high dielectric constant gate insulators

  KITAMURA Masatoshi, LEE Daeil, ARAKAWA Yasuhiko

  We report high-performance organic-based thin-film transistors (TFTs) with high dielectric constant gate insulators operating at low voltages. The gate insulators are Ti_<1-x>Si_xO_2 films, which were deposited by RF sputtering. The dielectric constant and surface roughness depends on the concentration of SiO_2 in Ti_<1-x>Si_xO_2 films. The Ti_<1-x>Si_xO_2 films with x ≥ 0.17 have flat surfaces. Pentacene TFTs with Ti_<1-x>Si_xO_2 gate insulators were fabricated and can operate at drain voltages of V_D≤-1 V at least. The field effect mobilities obtained at V_D≤-2 V are more than 1.0 cm^2/Vs. The pentacene TFT exhibits high performance with a threshold voltage of-1.6 V, an inverse subthreshold slope of 0.13 V/decade and a current on/off ratio of 1×10^7.

  The Institute of Electronics, Information and Communication Engineers, 11 Dec. 2006, IEICE technical report, 106(439) (439), 59 - 64, Japanese


• Enhanced Luminance Efficiency from Organic Light-Emitting Diodes with 2D Photonic Crystal

  KITAMURA Masatoshi, IWAMOTO Satoshi, ARAKAWA Yasuhiko

  15 Sep. 2004, Extended abstracts of the ... Conference on Solid State Devices and Materials, 2004, 160 - 161, English

• においのセンシング、分析とその可視化、数値化

  技術情報協会

  Contributor, 第５章第５節VOC検出のための気体センサの開発と肺がんスクリーニング, 技術情報協会, Oct. 2020, Japanese, ISBN: 9784861048104


• 匂いのセンシング技術

  中本, 高道

  第II編 第2章 酸化物半導体ガスセンサ, シーエムシー出版, Aug. 2020, Japanese, ISBN: 9784781315157


• IoTを指向するバイオセンシング・デバイス技術

  民谷, 栄一, 関谷, 毅, 八木, 康史

  Contributor, 第2章 第5節 電極表面処理技術と物性評価, シーエムシー出版, Nov. 2016, 145-153, Japanese, ISBN: 9784781311906

  Textbook


• 薄膜の評価技術ハンドブック

  吉田, 貞史, 金原, 粲

  Contributor, 第７章 第１節，第１項 過渡光電流解析，第３項 高周波伝導特性, テクノシステム, Jan. 2013, 415-417, 420-422, Japanese, ISBN: 9784924728677


• 有機トランジスタ材料の評価と応用

  工藤, 一浩, 森, 健彦, 長谷川, 達生

  Contributor, 第４章低電圧化, シーエムシー出版, 2005, 117-128, Japanese, ISBN: 4882315106

  Textbook


• Analysis of complex excitons and its optical properties = 多体励起子状態及びその光学応答に関する研究

  北村, 雅季

  Single work, 東京大学数理科学研究科, 2000

• フォトマスクを用いた酸化金のパターニング形成

  谷垣 賢, 村田 大樹, 服部 吉晃, 北村 雅

  薄膜材料デバイス研究会第20回研究集会, Nov. 2023, Japanese

  Poster presentation


• 光電子収量分光法によるIn7GaZnO13薄膜の仕事関数測定

  吉岡 賢司, 一楽 想大, 服部 吉晃, 北村 雅季

  薄膜材料デバイス研究会第20回研究集会, Nov. 2023, Japanese

  Poster presentation


• 二層構造InGaZnO4/In5GaZnO10から成る薄膜トランジスタの特性評価

  一楽 想大, 吉岡 賢司, 服部 吉晃, 北村 雅季

  薄膜材料デバイス研究会第20回研究集会, Nov. 2023, Japanese

  Poster presentation


• 光学顕微鏡を用いたチオール有機単分子膜のパターニング評価

  村田 大樹, 谷垣 賢, 服部 吉晃, 北村 雅季

  薄膜材料デバイス研究会第20回研究集会, Nov. 2023, Japanese

  Poster presentation


• Coverage control of a phosphonic acid monolayer on an InGaZnO surface

  Yudai Kitano, Yoshiaki Hattori, Masatoshi Kitamura

  The 9th International Symposium on Organic and Inorganic Electronic Materials and Related Nanotecnologies, Jun. 2023, English

  Poster presentation


• スパッタリングにより作製したIn5GaZnO10薄膜トランジスタの特性評価

  中野渡 俊喜, 渡邉 悠太, 服部 吉晃, 北村 雅季

  第70応用物理学関係連合講演会, Mar. 2023, Japanese

  Oral presentation


• 有機薄膜形成のためのインクジェット法による親水疎水パターニングを用いた液摘挙動制御

  津田 真太朗, 服部 吉晃, 井上 聡, 北村 雅季

  第70応用物理学関係連合講演会, Mar. 2023, Japanese

  Poster presentation


• 層状物質の厚い膜に存在する単層分の厚さの違いを検知する手法

  服部 吉晃, 谷口 尚, 渡邊 賢司, 北村 雅季

  第70応用物理学関係連合講演会, Mar. 2023, Japanese

  Poster presentation


• In5GaZnO10 薄膜をチャネル層とする電界効果トランジスタの特性評価

  中野渡 俊喜, 渡邉 悠太, 服部 吉晃, 北村 雅季

  薄膜材料デバイス研究会第19回研究集会, Nov. 2022, Japanese

  Poster presentation


• 光電子収量分光法によるInGaZnO薄膜のバンド構造解析

  渡邉 悠太, 中野渡 俊喜, 服部 吉晃, 北村 雅季

  薄膜材料デバイス研究会第19回研究集会, Nov. 2022, Japanese

  Poster presentation


• In5GaZnO10薄膜トランジスタの特性評価

  中野渡 俊喜, 渡邉 悠太, 服部 吉晃, 北村 雅季

  第83回応用物理学会秋季学術講演会, Sep. 2022, Japanese

  Poster presentation


• 大気中光電子収量分光法による原子比率の異なるInGaZnO 薄膜の仕事関数評価

  渡邉 悠太, 中野渡 俊喜, 服部 吉晃, 北村 雅季

  第83回応用物理学会秋季学術講演会, Sep. 2022, Japanese

  Poster presentation


• 塗布型有機薄膜トランジスタのためのUV/オゾン処理有機単分子膜の改質

  井上 聡, 服部 吉晃, 北村 雅季

  第83回応用物理学会秋季学術講演会, Sep. 2022, Japanese

  Poster presentation


• 大気中光電子収量分光法によるInGaZnO薄膜のエネルギーバンド構造解析

  渡邉 悠太, 服部 吉晃, 北村 雅季

  第69応用物理学関係連合講演会, Mar. 2022, Japanese

  Poster presentation


• 金極薄膜を用いた単層h-BNの可視化

  服部 吉晃, 谷口 尚, 渡邊 賢司, 北村 雅季

  第69応用物理学関係連合講演会, Mar. 2022, Japanese

  Oral presentation


• Organic thin-film transistors for high performance logic circuits: Realization of short channel, high mobility, low contact resistance and threshold voltage control

  Masatoshi Kitamura, Yoshiaki Hattori

  MRS FALL MEETING, Dec. 2021, English

  [Invited]

  Invited oral presentation


• 金属顕微鏡を用いたアルカンチオール単分子有機膜の可視化

  服部 吉晃, 北村 雅季

  薄膜材料デバイス研究会 第18回研究集会「結晶成長技術とデバイスの新展開」, Nov. 2021, Japanese

  Oral presentation


• 疎水性単分子膜を修飾した基板上への塗布法用い有機半導体薄形成技術

  濱田 拓巳, 井上 聡, 服部 吉晃, 北村 雅季

  応用物理学会関西支部 2021年度第２回講演会, Oct. 2021, Japanese

  Poster presentation


• 塗布法による有機半導体薄膜の製膜において 2度塗りした際の薄膜形成メカニズム

  近藤 隆介, 濱田 拓巳, 服部 吉晃, 北村 雅季

  応用物理学会関西支部 2021年度第２回講演会, Oct. 2021, Japanese

  Poster presentation


• Organic monolayers modified by ultraviolet-ozone for solutionprocessed organic thin-film transistors

  Satoshi Inoue, Yoshiaki Hattori, Masatoshi Kitamura

  11th International Conference on Flexbile and Printed Electronics, English

  Poster presentation


• 撥水性基板上にスピンコート法を用いて作製した有機薄膜ラジタの評価」

  井上 聡, 服部 吉晃, 北村 雅季

  応用物理学会関西支部 2021年度第１回講演会, Apr. 2021, Japanese

  Poster presentation


• 光電子収量分法による酸素プラズマ処理したSiO2絶縁膜表面のエネルギー準位分析

  渡邉 悠太, 服部 吉晃, 北村 雅季

  応用物理学会関西支部 2021年度第１回講演会, Apr. 2021, Japanese

  Poster presentation


• 光学顕微鏡による的異方性を持つ単分子有機薄膜の観察と画像処理解析

  津田 真太朗, 服部 吉晃, 北村 雅季

  応用物理学会関西支部 2021年度第１回講演会, Apr. 2021, Japanese

  Poster presentation


• Bottom-contact pentacene thin-film transistor with threshold voltages controlled by oxygen plasma treatment

  H. Fujita, Y. Kimura, Y. Hattori, M. Kitamura

  IEEE EDS Kansai Chapter 第20回「関西コロキアム電子デバイスワークショップ」, Nov. 2020, Japanese

  [Invited]

  Invited oral presentation


• 酸素プラズマ処理により生じる有機半導体／ゲート絶縁膜界面準位のエネルギー分布

  木村 由斉, 服部 吉晃, 北村 雅季

  薄膜材料デバイス研究会 第17回研究集会「薄膜デバイスの原点」, Nov. 2020, Japanese

  Oral presentation


• Evaluation of carrier mobility in organic metal-oxide-semiconductor capacitors

  Yoshinari Kimura, Yoshiaki Hattori, Masatoshi Kitamura

  39th Electronic Materials Symposium, Oct. 2020, Japanese

  Poster presentation


• Highly thermal-stable monolayers formed on a gold surface using benzenedithiol

  Hayato Takahashi, Naoki Ikematsu, Yoshiaki Hattori, Masatoshi Kitamura

  39th Electronic Materials Symposium, Oct. 2020, Japanese

  Poster presentation


• 酸素プラズマ処理が与える有機半導体/絶縁膜界面準位への影響

  木村 由斉, 服部 吉晃, 北村 雅季

  第67応用物理学関係連合講演会, Mar. 2020, Japanese

  Others


• 偏光顕微鏡を用いた単層DPh-DNTT二次元核の方位決定

  服部 吉晃, 北村 雅季

  第67応用物理学関係連合講演会, Mar. 2020, Japanese

  Others


• SnOx を用いたpチャネル薄膜トランジスタに対するスパッタパワーと圧力の影響

  宇賀治 瞭介, 岩佐 恒汰, 木村 由斉, 北村 雅季

  応用物理学会関西支部 2019年度第２回講演会, Nov. 2019, Japanese

  Poster presentation


• ガスセンサ応用に向けたSnO2薄膜トランジスタの電流安定性評価

  岩田 大輝, 岩佐 恒汰, 木村 由斉, 北村 雅季

  薄膜材料デバイス研究会 第16回研究集会, Nov. 2019, Japanese

  Poster presentation


• パッシベーション膜を有するpチャネルSnOx薄膜トランジスタ

  岩佐 恒汰, 岩田 大輝, 木村 由斉, 北村 雅季

  薄膜材料デバイス研究会 第16回研究集会, Nov. 2019, Japanese

  Poster presentation


• フルオロベンゼンチオールを電極表面に修飾した有機薄膜トランジスタ

  濱野 凌, 藤田 宏樹, 木村 由斉, 服部吉晃, 北村 雅季

  薄膜材料デバイス研究会 第16回研究集会, Nov. 2019, Japanese

  Oral presentation


• Statistical study of shape for submonolayer 2D islands of DPh-DNTT prepared by vacuum deposition

  Yoshiaki Hattori, Yoshinari Kimura, Masatoshi Kitamura

  38th Electronic Materials Symposium, Oct. 2019, Japanese

  Poster presentation


• 金表面に形成したベンゼンジチオール単分子膜の耐熱性評価

  高橋 勇人, 池松 直樹, 服部 吉晃, 北村 雅季

  第80回応用物理学会学術講演会, Sep. 2019, Japanese

  Poster presentation


• MOSキャパシタ構造を利用した有機半導体中のキャリア移動度評価

  木村 由斉, 服部 吉晃, 北村 雅季

  第80回応用物理学会学術講演会, Sep. 2019, Japanese

  Oral presentation


• 単層 DPh-DNTT の2次元アイランドにおける異方性

  服部 吉晃, 木村 由斉, 北村 雅季

  第80回応用物理学会学術講演会, Sep. 2019, Japanese

  Oral presentation


• 酸化物半導体ガスセンサの研究開発の現状：高感度水素検出に向けて

  北村 雅季

  第80回応用物理学会学術講演会, Sep. 2019, Japanese

  [Invited]

  Invited oral presentation


• Logic circuits consisting of pentacene thin-film transistors with controlled threshold voltages

  Hajime Takahashi, Masatoshi Kitamura, Yoshiaki Hattori, Yoshinari Kimura

  IEEE EDS Kansai Chapter 第19回「関西コロキアム電子デバイスワークショップ」, Sep. 2019, Japanese

  [Invited]

  Invited oral presentation


• Bottom-contact pentacene thin-film transistor with threshold voltages controlled by oxygen plasma treatment

  Hiroki Fujita, Yoshinari Kimura, Yoshiaki Hattori, Masatoshi Kitamura

  International Conference on Solid State Devices and Materials, Sep. 2019, English

  Poster presentation


• A p-channel SnOx thin-film transistor with a SiO2 passivation layer

  Kota Iwasa, Hiroki Iwata, Yoshinari Kimura, Masatoshi Kitamura

  7th International Workshop on Epitaxial Growth and Fundamental Properties of Semiconductor Nanostructure, Sep. 2019, English

  Poster presentation


• Current stability in SnO2 thin-film transistors with ultra-thin channel layers toward gas sensor application

  Hiroki Iwata, Kota Iwasa, Yoshinari Kimura, Masatoshi Kitamura

  7th International Workshop on Epitaxial Growth and Fundamental Properties of Semiconductor Nanostructure, Sep. 2019, English

  Poster presentation


• 有機薄膜トランジスタにおける酸素プラズマを用いたパターニング

  鳥羽 哲平, 服部 吉晃, 北村 雅季

  応用物理学会関西支部 2019年度第１回講演会, Jun. 2019, Japanese

  Poster presentation


• UV/ozone処理を用いた熱酸化膜上単分子膜の被覆率操作

  眞田 武, 北村 雅季, 服部 吉晃

  応用物理学会関西支部 2019年度第１回講演会, Jun. 2019, Japanese

  Poster presentation


• Surface properties of oriented polytetrafluoroethylene films with a micrometer pitch

  Yuki Matsuda, Yoshinari Kimura, Yoshiaki Hattori, Masatoshi Kitamura

  10th International Conference on Molecular Electronics and Bioelectronics, Jun. 2019, English

  Poster presentation


• The formation of a mixed monolayer on a gold surface toward surface property control

  Naoki Ikematsu, Hayato Takahashi, Yoshiaki Hattori, Masatoshi Kitamura

  10th International Conference on Molecular Electronics and Bioelectronics, Jun. 2019, English

  Poster presentation


• High thermal stability of the benzenedithiol monolayer formed on a gold surface

  Hayato Takahashi, Ikematsu Naoki, Yoshiaki Hattori, Masatoshi Kitamura

  10th International Conference on Molecular Electronics and Bioelectronics, Jun. 2019, English

  Poster presentation


• Nucleation and shape of 2D islands of DPh-DNTT thin-films prepared by vacuum evaporation

  Yoshiaki Hattori, Yoshinari Kimura, Masatoshi Kitamura

  Compound Semiconductor Week, May 2019, English

  Oral presentation


• Voltage and frequency dependence of capacitance characteristics in organic MOS capacitors

  Yoshinari Kimura, Yoshiaki Hattori, Masatoshi Kitamura

  Compound Semiconductor Week, May 2019, English

  Poster presentation


• Thin-film transistors based on copper phthalocyanine deposited on a gate dielectric rubbed with poly(tetrafluoroethylene)

  Shotaro Watanabe, Yoshinari Kimura, Yoshiaki Hattori, Masatoshi Kitamura

  Compound Semiconductor Week, May 2019, English

  Poster presentation


• 酸化物半導体薄膜のガスセンサ応用：揮発性有機化合物の識別可能性

  北村 雅季

  日本学術振興会透明酸化物光・電子材料第166委員会 第83回研究会, Apr. 2019, Japanese

  [Invited]

  Invited oral presentation


• 酸素プラズマ処理によるボトムコンタクト型有機トランジスタの閾値電圧制御

  藤田 宏樹, 吉岡 巧, 木村 由斉, 服部 吉晃, 北村 雅季

  第66応用物理学関係連合講演会, Mar. 2019, Japanese

  Poster presentation


• 有機MOSキャパシタの電圧・周波数特性解析

  木村 由斉, 服部 吉晃, 北村 雅季

  第66応用物理学関係連合講演会, Mar. 2019, Japanese

  Oral presentation


• 真空蒸着法におけるDNTTとその誘導体の核形成機構

  服部 吉晃, 木村 由斉, 吉岡 巧, 北村 雅季

  第66応用物理学関係連合講演会, Mar. 2019, Japanese

  Oral presentation


• ガスセンサ応用に向けた酸化スズ薄膜トランジスタの電流電圧特性の安定性評価

  岩田大輝, 木村 由斉, 北村 雅季

  応用物理学会関西支部 平成30年度第３回講演会, Feb. 2019


• 水晶振動子センサを用いたベンゼンチオール単分子膜に依存した大気中水分子吸着特性の評価

  KITAMURA Masaki, KITAMURA Masatoshi

  第64応用物理学関係連合講演会, Mar. 2017, Japanese, Domestic conference

  Oral presentation


• ガスセンサ・バイオセンサのための材料作製技術

  KITAMURA Masatoshi

  日本真空学会関西支部 第９回実用技術セミナー, Jan. 2017, Japanese, Domestic conference

  [Invited]

  Invited oral presentation


• Recent Research on Physical Electronics in the Department of Electrical and Electronic Engineering

  KITAMURA Masatoshi

  1st Bilateral Workshop on Research Exchange between National Taiwan University and Kobe University, Dec. 2016, English, International conference

  Invited oral presentation


• Fundamental technology for organic transistors and their application to sensor devices

  KITAMURA Masatoshi

  23rd International Display Workshops in conjunction with Asia Display, Dec. 2016, English, International conference

  [Invited]

  Invited oral presentation


• 背面露光法による自己整合電極を有するペンタセン薄膜トランジスタ

  TAKAHASHI Hajime, HANAFUSA Yuki, KITAMURA Masatoshi

  大阪府立大学21世紀化学研究機構 分子エレクトロニックデバイス研究所 第18回研究会, Nov. 2016, Japanese, Domestic conference

  Poster presentation


• 電極表面をベンゼンチオール誘導体で修飾したボトムコンタクト型C60トランジスタ

  HANAFUSA Yuki, TAKAHASHI Hajime, KITAMURA Masatoshi

  大阪府立大学21世紀化学研究機構 分子エレクトロニックデバイス研究所 第18回研究会, Nov. 2016, Japanese, Domestic conference

  Poster presentation


• デバイス応用のための界面・表面の物性制御 ～有機トランジスタの閾値電圧制御を中心に～

  KITAMURA Masatoshi

  大阪府立大学21世紀化学研究機構 分子エレクトロニックデバイス研究所 第18回研究会, Nov. 2016, Japanese, Domestic conference

  [Invited]

  Invited oral presentation


• アニールによるSnOx薄膜を利用したpチャネル薄膜トランジスタ

  OGAWA Hiroki, KITAMURA Masatoshi

  薄膜材料デバイス研究会 第13回研究集会, Oct. 2016, Japanese, Domestic conference

  Poster presentation


• 有機トランジスタの回路応用と閾値電圧制御

  KITAMURA Masatoshi

  電子情報通信学会 有機エレクトロニクスデバイス・材料に関する研究討論会, Sep. 2016, Japanese, Domestic conference

  [Invited]

  Invited oral presentation


• Optimization in microwave synthesis of copper phthalocyanine for organic thin-film transistors

  MIZUKA Shota, KITAMURA Masatoshi

  35th Electronic Materials Symposium, Jul. 2016, Japanese, Domestic conference

  Poster presentation


• 背面露光法を利用して作製した表面処理電極を有するペンタセン薄膜トランジスタ

  TAKAHASHI Hajime, HANAFUSA Yuki, KITAMURA Masatoshi

  第63応用物理学関係連合講演会, Mar. 2016, Japanese, 東京, Domestic conference

  Poster presentation


• ボトムコンタクト型フラーレンC60トランジスタの電極表面処理効果

  HANAFUSA Yuki, TAKAHASHI Hajime, KITAMURA Masatoshi

  第63応用物理学関係連合講演会, Mar. 2016, Japanese, 東京, Domestic conference

  Poster presentation


• 酸素プラズマ処理によるDNTTトランジスタの閾値電圧への影響

  KITANI Asahi, KIMURA Yoshinari, KITAMURA Masatoshi, ARAKAWA Yasuhiko

  応用物理学会関西支部 平成27年度第３回講演会, Feb. 2016, Japanese, 大阪, Domestic conference

  Poster presentation


• 高性能有機薄膜トランジスタの実現と新たな展開

  KITAMURA Masatoshi, ARAKAWA Yasuhiko

  ナノ量子情報エレクトロニクス連携研究拠点成果報告シンポジウム, Feb. 2016, Japanese, 東京, Domestic conference

  [Invited]

  Invited oral presentation


• スパッタリング製膜したSnOxのアニールにより作製したpチャネル薄膜トランジスタ

  OGAWA Hiroki, MORII Yasutaka, KITAMURA Masatoshi

  応用物理学会関西支部 平成27年度第３回講演会, Feb. 2016, Japanese, 大阪, Domestic conference

  Poster presentation


• 酸素プラズマ処理によるDNTTトランジスタの閾値電圧制御

  KITANI Asahi, KIMURA Yoshinari, KITAMURA Masatoshi, ARAKAWA Yasuhiko

  薄膜材料デバイス研究会 第12回研究集会, Oct. 2015, Japanese, 京都, Domestic conference

  Oral presentation


• ベンゼンチオール誘導体単分子膜を用いた金属表面の物性制御

  TATARA Shingo, KUZUMOT Yasutaka, KITAMURA Masatoshi

  応用物理学会関西支部 平成27年度第２回講演会, Sep. 2015, Japanese, 大阪, Domestic conference

  Poster presentation


• Physical properties of metal surfaces modified with substituted-benzenethiol

  TATARA Shingo, KUZUMOT Yasutaka, KITAMURA Masatoshi

  34th Electronic Materials Symposium, Jul. 2015, Japanese, 滋賀, Domestic conference

  [Invited]

  Poster presentation


• Annealing effect on the electrical properties in fluorinated copper phthalocyanine films for organic photovoltaic applications

  KUZUMOT Yasutaka, MIZUKA Shota, KITAMURA Masatoshi

  34th Electronic Materials Symposium, Jul. 2015, Japanese, 滋賀, Domestic conference

  [Invited]

  Poster presentation


• Wettability properties of substituted-benzenethiol monolayers on silver and gold surfaces

  TATARA Shingo, KUZUMOT Yasutaka, KITAMURA Masatoshi

  8th International Conference on Molecular Electronics and Bioelectronics, Jun. 2015, English, 東京, International conference

  [Invited]

  Poster presentation


• Operational Stability in Pentacene Thin-Film Transistors with Threshold Voltages Tuned by Oxygen Plasma Treatment

  KIMURA Yoshinari, KITAMURA Masatoshi, KITANI Asahi, ARAKAWA Yasuhiko

  5th International Symposium on Organic and Inorganic Electronic Materials and Related Nanotechnologies, Jun. 2015, English, 新潟, International conference

  [Invited]

  Oral presentation


• Dinaphthothienothiophen Thin-Film Transistors with Threshold Voltage Shift Induced by Oxygen Plasma

  KITANI Asahi, KIMURA Yoshinari, KITAMURA Masatoshi, Yasuhiko Arakawa

  8th International Conference on Molecular Electronics and Bioelectronics, Jun. 2015, English, 東京, International conference

  [Invited]

  Poster presentation


• Copper phthalocyanine synthesized by microwave irradiation and the application to thin-film transistors

  MIZUKA Shota, KITAMURA Masatoshi

  8th International Conference on Molecular Electronics and Bioelectronics, Jun. 2015, English, 東京, International conference

  [Invited]

  Poster presentation


• ベンゼンチオール誘導体修飾による金表面の物性変化：仕事関数とその熱安定性および水接触角

  KUZUMOT Yasutaka, TATARA Shingo, KITAMURA Masatoshi

  応用物理学会 有機分子・バイオエレクトロニクス分科会「有機分子・バイオエレクトロニクスの最新動向」, May 2015, Japanese, 富山, Domestic conference

  Oral presentation


• 有機薄膜トランジスタの研究開発～高性能・高機能トランジスタの実現を目指して～

  KITAMURA Masatoshi, ARAKAWA Yasuhiko

  東京大学ナノ量子情報エレクトロニクス研究機構 ナノ量子情報エレクトロニクスセミナー, Apr. 2015, Japanese, 東京, Domestic conference

  [Invited]

  Invited oral presentation


• 有機薄膜トランジスタの研究開発と実用化に向けた展望

  KITAMURA Masatoshi

  2015年総合大会講演論文集, Mar. 2015, Japanese, 電子情報通信学会, 滋賀, Domestic conference

  [Invited]

  Invited oral presentation


• ベンゼンチオール誘導体による修飾表面の濡れと安定性

  TATARA Shingo, KITAMURA Masatoshi

  第62応用物理学関係連合講演会, Mar. 2015, Japanese, 応用物理学会, 神奈川, Domestic conference

  Poster presentation


• Wettability Control of Gold Surfaces Modified with Benzenethiol Derivatives

  TATARA Shingo, KITAMURA Masatoshi

  11th International conference on Nano-Molecular Electronics, Dec. 2014, English, Kobe, International conference

  [Invited]

  Oral presentation


• 有機薄膜トランジスタの閾値電圧制御：集積回路応用に向けて

  KIMURA Yoshinari, KITAMURA Masatoshi, ARAKAWA Yasuhiko

  第75回応用物理学会学術講演会, Sep. 2014, Japanese, 応用物理学会, 札幌, Domestic conference

  Oral presentation


• ベンゼンチオール誘導体を用いた金属表面の濡れ性制御

  TATARA Shingo, KUZUMOT Yasutaka, KITAMURA Masatoshi

  第75回応用物理学会学術講演会, Sep. 2014, Japanese, 応用物理学会, 札幌, Domestic conference

  Poster presentation


• ジナフトチエノチオフェン骨格を有するn 型有機トランジスタ材料の設計

  MIZUKA Shoto, KITAMURA Masatoshi

  第75回応用物理学会学術講演会, Sep. 2014, Japanese, 応用物理学会, 札幌, Domestic conference

  Poster presentation


• Pentacene Thin-Film Transistors with Controlled Threshold Voltages andTheir Application to Pseudo CMOS Inverters

  KIMURA Yoshinari, KITAMURA Masatoshi, ARAKAWA Yasuhiko

  International Conference on Solid State Devices and Materials, Sep. 2014, English, Ibaragi, International conference

  [Invited]

  Oral presentation


• Annealing Effect on Field-Effect Mobilities in Bottom-Contact Alkylated Dinaphthothienothiophene Transistors

  KITAMURA Masatoshi, KUZUMOT Yasutaka, ARAKAWA Yasuhiko

  International Conference on Solid State Devices and Materials, Sep. 2014, English, Ibaragi, International conference

  [Invited]

  Oral presentation


• Threshold voltage control in organic thin-film transistors by oxygen plasma treatment

  KIMURA Yoshinari, KITAMURA Masatoshi, ARAKAWA Yasuhiko

  第33回電子材料シンポジウム, Jul. 2014, Japanese, Shizuoka, Domestic conference

  [Invited]

  Poster presentation


• 有機薄膜トランジスタの閾値電圧制御と擬似CMOS回路への応用

  KIMURA Yoshinari, KITAMURA Masatoshi, ARAKAWA Yasuhiko

  公開シンポジウム「ナノ量子情報エレクトロニクスの新展開」, May 2014, Japanese, 東京, Domestic conference

  Poster presentation


• 有機デバイス応用に向けたフッ素化銅フタロシアニンの膜構造および電気的特性に対するアニール効果

  KUZUMOT Yasutaka, KITAMURA Masatoshi

  公開シンポジウム「ナノ量子情報エレクトロニクスの新展開」, May 2014, Japanese, 東京, Domestic conference

  Poster presentation


• 高性能・高速動作有機薄膜トランジスタの開発

  KITAMURA Masatoshi, ARAKAWA Yasuhiko

  公開シンポジウム「ナノ量子情報エレクトロニクスの新展開」, May 2014, Japanese, 東京, Domestic conference

  Nominated symposium


• Solution-processed organic thin-film transistors

  KITAMURA Masatoshi

  6th Asian Coating Workshop, May 2014, English, Kobe, International conference

  [Invited]

  Invited oral presentation


• 閾値電圧制御された有機トランジスタから成る擬似CMOS回路

  KIMURA Yoshinari, KITAMURA Masatoshi, ARAKAWA Yasuhiko

  第61応用物理学関係連合講演会, Mar. 2014, Japanese, 応用物理学会, 神奈川, Domestic conference

  Oral presentation


• 表面処理電極を有するボトムコンタクト型アルキルDNTTトランジスタ

  KITAMURA Masatoshi, KIMURA Yoshinari, ARAKAWA Yasuhiko

  第61応用物理学関係連合講演会, Mar. 2014, Japanese, 応用物理学会, 神奈川, Domestic conference

  Oral presentation


• フッ素化銅フタロシアニンの膜構造および電気的特性へのアニール効果

  KUZUMOT Yasutaka, MATSUYAMA Hirotaka, KITAMURA Masatoshi

  第61応用物理学関係連合講演会, Mar. 2014, Japanese, 応用物理学会, 神奈川, Domestic conference

  Poster presentation


• 擬似CMOS 回路への応用に向けた有機薄膜トランジスタの閾値電圧制御

  KIMURA Yoshinari, KITAMURA Masatoshi, ARAKAWA Yasuhiko

  第10回研究集会「薄膜デバイスの応用展開」, Oct. 2013, Japanese, 薄膜材料デバイス研究会, 京都, Domestic conference

  Oral presentation


• 有機トランジスタは実用化されるか ～ 若手研究者に向けて～

  KITAMURA Masatoshi

  第４回 有機分子・バイオエレクトロニクスの未来を拓く若手研究者討論会, Sep. 2013, Japanese, 応用物理学会 有機分子・バイオエレクトロニクス分科会, 京都, Domestic conference

  Invited oral presentation


• 酸素プラズマ処理による有機トランジスタの閾値電圧精密制御

  KIMURA Yoshinari, KATSUKI Kazuma, KITAMURA Masatoshi, ARAKAWA Yasuhiko

  第74回応用物理学会学術講演会, Sep. 2013, Japanese, 応用物理学会, 京都, Domestic conference

  Oral presentation


• ボトムコンタクト型アルキルDNTT 薄膜トランジスタの安定性評価

  KITAMURA Masatoshi, ARAKAWA Yasuhiko

  第74回応用物理学会学術講演会, Sep. 2013, Japanese, 応用物理学会, 京都, Domestic conference

  Poster presentation


• Thermal Stability of Short Channel, High-Mobility Organic Thin-Film Transistors having Bottom-Contact Configuration

  KITAMURA Masatoshi, ARAKAWA Yasuhiko

  Society for Information Display International Symposium, Sep. 2013, English, The Japan Society of Applied Physics, Fukuoka, International conference

  [Invited]

  Poster presentation


• Structural and Electrical Properties of Fluorinated Copper Phthalocyanine for Organic Photovoltaics

  KUZUMOT Yasutaka, MATSUYAMA Hirotaka, KITAMURA Masatoshi

  Society for Information Display International Symposium, Sep. 2013, English, The Japan Society of Applied Physics, Fukuoka, International conference

  [Invited]

  Oral presentation


• Threshold Voltage Control in Pentacene Thin-Film Transistors by Oxygen Plasma Treatment

  KIMURA Yoshinari, KATSUKI Kazuma, KITAMURA Masatoshi, KUZUMOT Yasutaka, ARAKAWA Yasuhiko

  40th International Symposium on Compound Semiconductors, May 2013, English, The Japan Society of Applied Physics, Fukuoka, International conference

  [Invited]

  Poster presentation


• Short-Channel, High-Mobility Organic Thin-Film Transistors with Alkylated Dinaphthothienothiophene

  KITAMURA Masatoshi, KUZUMOT Yasutaka, ARAKAWA Yasuhiko

  40th International Symposium on Compound Semiconductors, May 2013, English, The Japan Society of Applied Physics, Fukuoka, International conference

  [Invited]

  Oral presentation


• Fine tuning of energy levels in partially fluorinated copper phthalocyanine for organic photovoltaics

  KUZUMOT Yasutaka, MATSUYAMA Hirotaka, KITAMURA Masatoshi

  40th International Symposium on Compound Semiconductors, May 2013, English, The Japan Society of Applied Physics, Fukuoka, International conference

  [Invited]

  Poster presentation


• 酸素プラズマ処理による有機薄膜トランジスタの閾値電圧制御

  KIMURA Yoshinari, KATSUKI Kazuma, TANAKA Yoku, KITAMURA Masatoshi, ARAKAWA Yasuhiko

  第60応用物理学関係連合講演会, Mar. 2013, Japanese, 応用物理学会, 神奈川, Domestic conference

  Poster presentation


• アルミ電極を有するアルキルDNTT薄膜トランジスタ

  KATSUKI Kazuma, KIMURA Yoshinari, TANAKA Yoku, KITAMURA Masatoshi, ARAKAWA Yasuhiko

  第60応用物理学関係連合講演会, Mar. 2013, Japanese, 応用物理学会, 神奈川, Domestic conference

  Poster presentation


• Partially Fluorinated Copper Phthalocyanine toward Band Engineering for High-Efficiency Organic Photovoltaics

  KUZUMOT Yasutaka, MATSUYAMA Hirotaka, KITAMURA Masatoshi

  7th International Conference Molecular Electronics and Bioelectronics, Mar. 2013, English, Division of Molecular Electronics and Bioelectronics- The Japan Society of Applied Physics, Fukuoka, International conference

  [Invited]

  Oral presentation


• Dinaphthothienothiophene Thin-Film Transistors with Aluminum/Molybdenum Oxide Electrodes

  KITAMURA Masatoshi, ARAKAWA Yasuhiko

  7th International Conference Molecular Electronics and Bioelectronics, Mar. 2013, English, Division of Molecular Electronics and Bioelectronics- The Japan Society of Applied Physics, Fukuoka, International conference

  [Invited]

  Poster presentation


• 高性能有機CMOS回路－高速動作はどこまで可能か－

  KITAMURA Masatoshi, ARAKAWA Yasuhiko

  第9回研究集会「薄膜デバイスの未来」, Nov. 2012, Japanese, 薄膜材料デバイス研究会, 奈良, Domestic conference

  Invited oral presentation


• 高移動度ボトムコンタクト型アルキルDNTT薄膜トランジスタ

  KITAMURA Masatoshi, TANAKA Yoku, KANG Woogun, ARAKAWA Yasuhiko

  第73回応用物理学会学術講演会, Sep. 2012, Japanese, 応用物理学会, 愛媛, Domestic conference

  Oral presentation


• ボトムコンタクト型DNTT薄膜トランジスタの大気安定性

  TANAKA Yoku, KITAMURA Masatoshi, KANG Woogun, ARAKAWA Yasuhiko

  第73回応用物理学会学術講演会, Sep. 2012, Japanese, 応用物理学会, 愛媛, Domestic conference

  Poster presentation


• インクジェット印刷法による高性能C60薄膜トランジスタ

  KANG Woogun, KITAMURA Masatoshi, ARAKAWA Yasuhiko

  第73回応用物理学会学術講演会, Sep. 2012, Japanese, 応用物理学会, 愛媛, Domestic conference

  Invited oral presentation


• Threshold Voltage Shift of Inkjet-Printed C8-BTBT Thin-Film Transistors

  KANG Woogun, KITAMURA Masatoshi, ARAKAWA Yasuhiko

  The 2012 International Conference on Flexible and Printed Electronics, Sep. 2012, English, Tokyo, International conference

  [Invited]

  Oral presentation


• Dinaphtho Thieno Thiophene Thin-Film Transistors with Modified Platinum Electrodes in Bottom-Contact Configuration

  KITAMURA Masatoshi, TANAKA Yoku, KANG Woogun, ARAKAWA Yasuhiko

  International Conference on Solid State Devices and Materials, Sep. 2012, English, The Japan Society of Applied Physics, Kyoto, International conference

  [Invited]

  Oral presentation


• High-Performance Ink-Jet-Printed TFTs on Solution Wetting Polymer Gate Dielectric Layer

  KANG Woogun, KITAMURA Masatoshi, ARAKAWA Yasuhiko

  Society for Information Display International Symposium, Jun. 2012, English, Boston, International conference

  [Invited]

  Poster presentation


• 有機半導体を用いた高性能CMOSのための n 型 半導体基板開発

  北村 雅季, 竹谷 純一

  第2回物質・デバイス領域共同研究拠点活動報告会, Apr. 2012, Japanese, 物質・デバイス領域共同研究拠点, 東京, Domestic conference

  Others


• Solution-processed C60 Single Crystal Field-effect Transistors

  KANG Woogun, KITAMURA Masatoshi, ARAKAWA Yasuhiko

  Materials Research Society Spring Meeting, Apr. 2012, English, San Francisco, International conference

  [Invited]

  Oral presentation


• Solution-processed C60 Single Crystal Field-effect Transistors

  KANG Woogun, KITAMURA Masatoshi, ARAKAWA Yasuhiko

  Materials Research Society Spring Meeting,, Apr. 2012, English, Materials Research Society, USA, International conference

  [Invited]

  Oral presentation


• 白金電極を有するボトムコンタクト型DNTT薄膜トランジスタ

  北村 雅季, 奥田 修平, 荒川 泰彦

  第59応用物理学関係連合講演会, Mar. 2012, Japanese, 応用物理学会, 東京, Domestic conference

  Poster presentation


• 酸化モリブデン／アルミ電極を有するDNTT薄膜トランジスタ/アルミ電極を有するDNTT薄膜トランジスタ

  奥田 修平, 北村 雅季, 荒川 泰彦

  第59応用物理学関係連合講演会, Mar. 2012, Japanese, 応用物理学会, 東京, Domestic conference

  Poster presentation


• インクジェット法による高均一非晶質C60薄膜の作製と高移動度(＞2.4 cm2／V・s) n-channelトランジスタの実現/V・s) n-channelトランジスタの実現

  康 宇建, 北村 雅季, 荒川 泰彦

  第59応用物理学関係連合講演会, Mar. 2012, Japanese, 応用物理学会, 東京, Domestic conference

  Oral presentation


• 有機半導体を用いた高性能CMOSのための n 型 半導体基板開発

  北村 雅季, 竹谷 純一

  平成23年度 物質・デバイス共同研究拠点 共同研究 特定研究[A-4] ワークショップ, Feb. 2012, Japanese, 物質・デバイス領域共同研究拠点, 大阪, Domestic conference

  Others


• Solution-processed C60 field-effect transistors with high mobility

  KANG Woogun, KITAMURA Masatoshi, KAMURA Masakazu, AOMORI Shigeru, ARAKAWA Yasuhiko

  International Conference on Solid State Devices and Materials, Sep. 2011, English, The Japan Society of Applied Physics, Aichi, International conference

  [Invited]

  Oral presentation


• High-frequency-operating organic thin-film transistors and CMOS circuits

  KITAMURA Masatoshi

  5th East Asia Symposium on Functional Dyes & Advanced Materials, Sep. 2011, English, East Asia Symposium, China, International conference

  [Invited]

  Invited oral presentation


• 塗布工程による高移動度C60薄膜トランジスタの作製

  康 宇建, 北村 雅季, 青森 繁, 荒川 泰彦

  第72回応用物理学会学術講演会, Aug. 2011, Japanese, 応用物理学会, 山形, Domestic conference

  Oral presentation


• 高速動作有機CMOSリングオシレータ:発振周波数 200 kHz

  北村 雅季, 葛本 恭崇, 青森 繁, 荒川 泰彦

  第72回応用物理学会学術講演会, Aug. 2011, Japanese, 応用物理学会, 山形, Domestic conference

  Oral presentation


• 化学結合で積層したオリゴチオフェン積層膜と同じ分子構造を有するLB膜の分子配向の比較

  香村 勝一, 伊藤 哲二, 青森 繁, 大江 昌人, 北村 雅季, 荒川 泰彦

  第72回応用物理学会学術講演会, Aug. 2011, Japanese, 応用物理学会, 山形, Domestic conference

  Oral presentation


• 高速動作有機トランジスタに向けた有機無機界面制御

  KITAMURA Masatoshi

  応用物理学会 M&BE研究会「有機分子・バイオエレクトロニクスの動向と展望」, Jun. 2011, Japanese, 応用物理学会 有機分子・バイオエレクトロニクス分科会, 神戸, Domestic conference

  [Invited]

  Oral presentation


• 200-kHz-operation of organic CMOS ring oscillator

  KITAMURA Masatoshi, KUZUMOT Yasutaka, AOMORI Shigeru, ARAKAWA Yasuhiko

  30th Electronic Materials Symposium, Jun. 2011, English, Electronic Materials Symposium, Shiga, Domestic conference

  [Invited]

  Oral presentation


• Solution processed C60 fullerene thin-film transistors

  KANG Woogun, KITAMURA Masatoshi, ARAKAWA Yasuhiko

  第58応用物理学関係連合講演会, Mar. 2011, Japanese, 応用物理学会, 神奈川, Domestic conference

  Others


• Rectification Properties of Pentacene Transistor Diodes

  KITAMURA Masatoshi, ARAKAWA Yasuhiko

  第58応用物理学関係連合講演会, Mar. 2011, Japanese, 応用物理学会, 神奈川, Domestic conference

  Others


• Frequency property of a rubrene single-crystal field-effect transistor

  KITAMURA Masatoshi, UEMURA Takafumi, TAKEYA Jun, ARAKAWA Yasuhiko

  6th International Conference on Molecular Electronics and Bioelectronics, Mar. 2011, English, The Japan Society of Applied Physics, Division of Molecular Electronics and Bioelectronics, JSAP, Miyagi, International conference

  [Invited]

  Others


• A high frequency organic CMOS ring oscillator operating at 100 kHz

  KITAMURA Masatoshi, ARAKAWA Yasuhiko

  6th International Conference on Molecular Electronics and Bioelectronics, Mar. 2011, English, The Japan Society of Applied Physics, Division of Molecular Electronics and Bioelectronics, JSAP, Miyagi, International conference

  [Invited]

  Others


• 量子ドットを有する微小共振器レーザの構造の作製

  西岡政雄, 北村雅季, 石田悟己, 荒川泰彦

  第56回応用物理学会学術講演会, Aug. 1995, Japanese


• マルチステップを利用した InGaAs 量子ドットの自然配列

  北村雅季, 西岡政雄, 荒川泰彦

  第42回応用物理学関係連合講演会, Mar. 1995, Japanese


• 格子不整合を利用したマルチステップ上の InGaAs 量子細線の作製

  北村雅季, 荒川太郎, 西岡政雄, 荒川泰彦

  第42回応用物理学関係連合講演会, Mar. 1995, Japanese


• In-situ Fabrication of Self-Aligned InGaAs Quantum Dots on GaAs Multi-Atomic Steps by MOCVD

  M. Kitamura, M. Nishioka, J. Oshinowo, Y. Arakawa

  14th Electronic Materials Symposium, 1995, Japanese

  Poster presentation


• BEM-FDM 結合法を用いたスフェロマック・プラズマの MHD 平衡解析

  北村雅季, 神谷淳

  第5回情報処理学会東北支部研究会, Mar. 1994, Japanese

  Oral presentation

• THE JAPAN SOCIETY OF APPLIED PHYSICS

• ヘテロ接合型薄膜デバイスへの応用に向けた酸化インジウム化合物のバンド構造制御

  北村 雅季, 石田 謙司, 服部 吉晃

  日本学術振興会, 科学研究費助成事業, 基盤研究(B), 神戸大学, 01 Apr. 2024 - 31 Mar. 2028


• 超フレキシブル有機圧電型発電/拍動検知デバイス開発と生体内駆動の検証

  石田 謙司, 北村 雅季, 高嶋 一登, 小柴 康子, 堀家 匠平

  日本学術振興会, 科学研究費助成事業, 基盤研究(A), 神戸大学, Apr. 2021 - Mar. 2024

  本年度は、フレキシブル有機強誘電体フィルムの作製、強誘電/圧電特性の基礎評価に加え、心臓拍動のように臓器変形が伝搬していく複雑な臓器変形を検知するため、多素子センサを作製し、多点測定を試みた。PENフィルム上に、下部電極としてAl100 nmを真空蒸着した後、強誘電性高分子P(VDF/TrFE)をスピンコート成膜した。上部電極としてAl薄膜を真空蒸着し、キャパシタ型圧電センサーとした。上下電極はパターニングすることで、9つの圧電センサからなる拍動検出用センサー素子とした。デバイス保護、生体適合性のため、素子全面には気相重合法によりparylene Cを堆積してデバイス封止した。全センサー部をポーリング処理し、分極方向を一方向に揃え、かつ残留分極量Prを60mC/m2に揃えた。成人男性3D-X線CT画像から復元した心臓拍動モデルに、試作した多素子センサを貼り付け、正常拍動(60bpm)におけるセンサー出力を詳細解析した。すべての素子で、心臓モデル収縮時に負、膨張時に正の出力電圧が得られたが、センサ貼り付け位置によって出力電圧のピーク時間と電圧値には違いを観察した。「ピーク時間」の違いは拍動挙動（動き方）が場所によって異なることを、「電圧値の違い」は変位速度が異なること示差しており、心臓モデルの変形が右心室から左心室側へ伝搬していく複雑な心拍挙動の観測に成功した。また出力電圧の時間変化を圧電方程式に基づき応力変換することで、心臓モデル表面にかかる応力を計算した。心臓の電気的活動を体表電極で読み取る心電図と異なり、試作したフレキシブル圧電フィルムは心臓変形そのものをリアルタイム検出しており、かつ心臓表面にかかる応力（心筋力）が検出可能であることから、心膜炎等の心臓組織表面の疾患の早期発見が可能であると考えられる。また新規導入したマスクレス露光機の立ち上げ、及び条件出しも行った。


• Fundamental development for realization of high-performance organic transistors based on molecular orientation and interface control

  Kitamura Masatoshi

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B), Grant-in-Aid for Scientific Research (B), Kobe University, Apr. 2019 - Mar. 2022

  For improvement of the characteristics of organic transistors, we worked on the control of the gate insulator surface and the control of the organic semiconductor-metal interface. Regarding the control of the insulating film surface, the organic monolayer was appropriately surface-treated to enable the film formation process by the coating process, and the spin coating method achieved mobilities exceeding 4 cm2 / Vs. Regarding the control of the organic semiconductor-metal interface, we clarified the relationship between the organic monolayer and the work function, and found the organic monolayer appropriate for improvement of the characteristics in organic transistors. Regarding the control of the gate insulator surface, we reproduced the threshold voltage control by the surface treatment, and successfully estimated the density of the energy level generated by the treatment.


• Piezoelectric power generation with organic flexible ferroelectic polymers for implantable devices

  Ishida Kenji

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Challenging Research (Pioneering), Challenging Research (Pioneering), Kobe University, Jun. 2017 - Mar. 2020

  Flexible piezoelectric devices with poly (vinylidene fluoride-trifluoroethylene) thin films were fabricated, and directly monitoring of the heart state and piezoelectric power generation were investigated using the pulsating 3D heart model. By attaching the flexible piezoelectric devices to the 3D heart model, the piezoelectric responses corresponding to the pulsation of the right and left ventricles were observed and reflected the status of heart. The maximum output voltage was obtained in the front of the right ventricle of the heart model. The output energy, which caused from piezoelectric effect, improved linearly with the increase of the device area, and was estimated to be approximately 8 nJ/mm2 per heartbeat.


• Basic technology development of organic transistors for high-frequency-operating organic CMOS circuits

  KITAMURA Masatoshi

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), Grant-in-Aid for Scientific Research (C), Kobe University, Apr. 2012 - Mar. 2015, Principal investigator

  The basic technology development for realization of high-frequency operating organic-transistor circuits leaded to the following achievement. Surface treatment for contact electrodes and optimization of fabrication process realized a high mobility of 3.3 cm2/Vs in organic transistors with bottom contact configuration that is easily applied to short channel transistors. Also, threshold voltage control in the range of a few V was demonstrated by oxygen plasma treatment. Furthermore, the work function and the thermal stability of surface-modified electrodes for low contact resistance were investigated. As a result, work functions in the range of 4.3 to 5.5 eV were obtained.

  Competitive research funding


• 有機半導体に関する研究

  Competitive research funding


• Study on Organic Semiconductor

  Competitive research funding

• 有機デバイス用電極、及びそれを備えた有機デバイス

  葛本 恭崇, 北村 雅季

  特願2014-117870, 06 Jun. 2014, Sharp Corporation, 特開2015-231028, 21 Dec. 2015, 特許6326297, 20 Apr. 2018

  Patent right


• 有機光電変換素子

  葛本 恭崇, 北村 雅季

  特願2014-131501, 26 Jun. 2014, シャープ株式会社;国立大学法人 神戸大学, 特開2015-130480, 16 Jul. 2015

  Patent right


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