Bunjiro Tsujiyama

NTT (Japan)

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Haruki Kozawaguchi

Niigata University of Health and Welfare

Takashi Unagami

Teikyo University

S. Seki

Shiga Medical Center

Junichi Ohwaki

NTT (Japan)

Osamu Kogure

NTT (Japan)

Katsuhiko Hirabayashi

NTT (Japan)

Shunji Seki

NTT (Japan)

Yasuaki Tamura

NTT (Japan)

Kei Murase

Hot Springs Research Institute of Kanagawa Prefecture

Shoji Seki

Nitto (United States)

Cooperative Institutions

NTT (Japan)

NTT (United States)

Tohoku University

The University of Tokyo

NTT (Italy)

Nagoya University

NTT Basic Research Laboratories

Tokai University

Osaka University

Ibaraki University

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Red Electroluminescence and Crystallinity of ZnS:SmF₃ Thin Films

Japanese Journal of Applied Physics (1984)

Junichi Ohwaki Bunjiro Tsujiyama Haruki Kozawaguchi

The dependence of the red emission characteristics (emission efficiency, brightness and emission decay time) and crystallinity of ZnS:SmF 3 thin-film electroluminescent (TFEL) devices upon fabrication parameters such as the SmF 3 concentration and substrate temperature during evaporation, has been investigated. The electroluminescent characteristics are considered to be influenced more by the SmF 3 concentration and the grain height in the film thickness direction, than by the cubic ZnS structure {111} plane orientation and the film uniformity, or by the degree to which the cubic {111} plane is oriented parallel to the substrate. A bright red electroluminescence of 1000 cd/m 2 under 5 kHz sinusoidal voltage excitation and an emission efficiency of 0.078 lm/W are obtained in these ZnS:SmF 3 TFEL devices.

10.1143/jjap.23.699

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Citations (21)

Thin-Film Electroluminescent Device Employing Ta₂O₅ RF Sputtered Insulating Film

Japanese Journal of Applied Physics (1982)

Haruki Kozawaguchi Bunjiro Tsujiyama Kei Murase

In order to fabricate low-voltage-driven high-brightness thin-film electroluminescent devices, the emission characteristics of devices employing low dielectric loss Ta 2 O 5 RF-sputtered insulating films have been studied in comparison with those of devices employing Y 2 O 3 , Sm 2 O 3 and Al 2 O 3 deposited insulators. It was found that the devices employing Ta 2 O 5 , RF-sputtered films exhibited higher brightness, lower driving voltage and higher stability than the other devices. In addition, no aging was observed in the Ta 2 O 5 insulated devices. These results indicate that the Ta 2 O 5 RF-sputtered film is suitable as the insulating film in thin-film electroluminescent devices, and that the properties of the insulating film are closely related to the emission characteristics in such devices.

Electroluminescent display

10.1143/jjap.21.1028

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Citations (22)

An outline of electroluminescent devices.

Hyomen Kagaku (1988)

Bunjiro Tsujiyama

Recently, the electroluminescent (EL) technology has made a great progress in developing multi-color panels. In this paper, first, both AC and DC ZnS electroluminescent display devices having powder or thin film structures are reviewed, and their properties and characteristics are discussed. Secondly, the present fabrication techniques are outlined, and finally, the state of the arts in the electroluminescent display devices and its future trends also are discussed.

Electroluminescent display

10.1380/jsssj.9.276

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Citations (0)

High Transconductance Si-TFT's Using Ta2O5 Films as Gate Insulators

Extended Abstracts of the 2020 International Conference on Solid State Devices and Materials (1984)

Shunji Seki Takashi Unagami Bunjiro Tsujiyama

Transconductance

10.7567/ssdm.1984.b-12-5

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Citations (1)

Leakage current characteristics of offset-gate-structure polycrystalline-Silicon MOSFET's

IEEE Electron Device Letters (1987)

S. Seki Osamu Kogure Bunjiro Tsujiyama

Leakage current characteristics of offset-gate-structure polycrystalline-silicon (poly-Si) MOSFET's are studied as a function of dopant concentration N off in offset-gate regions. Leakage current markedly decreases from 1 × 10 ^-9 to 2 × 10 ^-11 A at V D = 10 V as N off is varied from 1 × 10 ¹⁸ to 1 × 10 ¹⁷ cm ^-3 . A maximum ON/OFF current ratio of 10 ⁸ is obtained at 1 × 10 ¹⁷ cm ^-3 . Calculations based on a quasi-two-dimensional model indicate that the reduction of leakage current is attributable to a decrease of the maximum lateral electric field strength in the drain depletion region. An analysis of the leakage current characteristics in terms of carrier emission from grain-boundary traps implies that thermonic emission accompanied by thermally assisted tunneling could be the dominant mechanism in determining leakage current.

10.1109/edl.1987.26684

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Citations (83)

p-Channel TFT's using magnetron-sputtered Ta₂O₅films as gate insulators

IEEE Electron Device Letters (1984)

S. Seki Takashi Unagami Bunjiro Tsujiyama

Metal-gate thin-film transistors (TFT's) have been fabricated in layers of laser-recrystallized polycrystalline silicon on fused quartz substrates at processing temperatures below 625°C. Tantalum pentoxide (Ta 2 O 5 ) was used as a gate insulator instead of a conventional thermally grown silicon dioxide (SiO 2 ). Ta 2 O 5 gate insulator was deposited onto the recrystallized silicon layer at room temperature, using an RF-magnetron sputtering system. The reactive ion etching method, using CF 4 as a reactive gas, was employed in patterning deposited Ta 2 O 5 . These TFT's have exhibited p-channel depletion-mode characteristics with a threshold voltage of 2.5 V and a transconductance of 70 µS at V g = - 2 V. An on-off current ratio exceeding 10 ⁵ has been obtained.

Polycrystalline silicon

10.1109/edl.1984.25885

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Citations (5)

The Role of Stacked Insulating Layers on Thin-Film Electroluminescent Devices

Japanese Journal of Applied Physics (1987)

Junichi Ohwaki Noriyoshi Yamauchi Haruki Kozawaguchi Bunjiro Tsujiyama

The charge versus applied voltage ( Q – V ) characteristics of a thin-film electroluminescent (TFEL) device with an Al/SiO 2 /Ta 2 O 5 /ZnS/Ta 2 O 5 /ITO/Glass structure are investigated. The results for a stacked insulating layer TFEL device are summarized as follows. The maximum charge ( Q max ) of the TFEL device is determined by the highest Q max of insulators. The SiO 2 insulating layer used in this study shows that the dielectric avalanche breakdown and the electric field of the film is clamped in the region above its own breakdown field strength under current conditions limited by the Ta 2 O 5 insulating layers. The TFEL device shows a hexagonal Q – V loop in high electric fields.

Dielectric strength

10.1143/jjap.26.1064

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Citations (6)

One-Dimensional Ising Model with General Spin

Journal of Mathematical Physics (1967)

Masuo Suzuki Bunjiro Tsujiyama Shigetoshi Katsura

The one-dimensional Ising model with general spin S has been formulated as an eigenvalue problem of order 2S + 1. Two methods to reduce the order to [S + 1] have been developed for calculating the energy and the susceptibility at zero external field. Exact solutions for S = 32 and S = 1 have been obtained. Numerical calculations of S = 32, 1, and ½ have been compared.

Square-lattice Ising model

Zero (linguistics)

10.1063/1.1705089

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Citations (95)

AC Powder Electroluminescence Maintenance Improvement

Journal of The Electrochemical Society (1983)

Katsuhiko Hirabayashi Haruki Kozawaguchi Bunjiro Tsujiyama

The effects of annealing and quenching EL phosphors on their maintenance are investigated. Annealing at a temperature from 700° to 1000°C for more than 1 hr in or air, and quenching are most efficient for EL life improvement. For example, EL phosphor annealed in air at 900°C for 2 hr and quenched has a half‐life of more than 3000 hr (initial ). Sulfur vacancy density, dopant content, and phosphor particle size are not changed appreciably by annealing, but the x‐ray diffraction peak intensity changes, and the activation energy of deterioration increases from 0.3 to 0.45 eV by annealing. These results suggest that the crystal quality is changed by annealing and quenching.

10.1149/1.2119611

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Citations (2)

Electrical Characteristics of Tantalum Pentoxide‐Silicon Dioxide‐Silicon Structures

Journal of The Electrochemical Society (1985)

S. Seki Takashi Unagami Bunjiro Tsujiyama

Electrical characteristics for metal‐tantalum pentoxide‐silicon dioxide‐silicon structures are described. The interface charge density and the surface‐state density are measured to determine the interface properties. By optimizing each insulator thickness, the interface charge density can be reduced to as low as at flatband. The surface‐state density of can be obtained near the midgap by inserting a 25 nm thickness of . It is indicated that the interface charge density variation with each insulator thickness can be explained by the charge compensation mechanism between the positive charge at interface and the negative charge at interface. It is found that the negative charge localized at interface gradually decreases and that the dielectric constant for deposited on monotonically increases with the underlying layer thickness.

Tantalum pentoxide

Silicon dioxide

Charge density

Pentoxide

10.1149/1.2113761

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Citations (10)