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Search Results: 1 - 10 of 855 matches for " Kiyokazu Nakagawa "
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Selective Heating of Transition Metal Usings Hydrogen Plasma and Its Application to Formation of Nickel Silicide Electrodes for Silicon Ultralarge-Scale Integration Devices  [PDF]
Tetsuji Arai, Hiroki Nakaie, Kazuki Kamimura, Hiroyuki Nakamura, Satoshi Ariizumi, Satoki Ashizawa, Keisuke Arimoto, Junji Yamanaka, Tetsuya Sato, Kiyokazu Nakagawa, Toshiyuki Takamatsu
Journal of Materials Science and Chemical Engineering (MSCE) , 2016, DOI: 10.4236/msce.2016.41006
Abstract:

We developed an apparatus for producing high-density hydrogen plasma. The atomic hydrogen density was 3.1 × 1021 m?3 at a pressure of 30 Pa, a microwave power of 1000 W, and a hydrogen gas flow rate of 10 sccm. We confirmed that the temperatures of transition-metal films increased to above 800C within 5 s when they were exposed to hydrogen plasma formed using the apparatus. We applied this phenomenon to the selective heat treatment of nickel films deposited on silicon wafers and formed nickel silicide electrodes. We found that this heat phenomenon automatically stopped after the nickel slicidation reaction finished. To utilize this method, we can perform the nickel silicidation process without heating the other areas such as channel regions and improve the reliability of silicon ultralarge-scale integration devices.

Feasibility Study to Evaluate Lattice-Space Changing of a Step-Graded SiGe/Si (110) Using STEM Moiré  [PDF]
Junji Yamanaka, Mai Shirakura, Chiaya Yamamoto, Kei Sato, Takane Yamada, Kosuke O. Hara, Keisuke Arimoto, Kiyokazu Nakagawa, Akimitsu Ishizuka, Kazuo Ishizuka
Journal of Materials Science and Chemical Engineering (MSCE) , 2018, DOI: 10.4236/msce.2018.67002
Abstract:
A moiré between crystal lattice planes and scanning electron beam-lines formed in a scanning transmission electron microscope includes the information of the lattice spacing. We apply these phenomena to a compositionally graded SiGe thin film deposited onto a Si substrate by molecular beam epitaxy method. The results of the experiments and image analysis show the potential of this technique to analyze a slight change of the lattice spacing according to a compositional change.
TEM and STEM Observations of a Flat Continuous Silicon-Germanium Thin Film Epitaxially Grown on Porous Silicon  [PDF]
Junji Yamanaka, Noritaka Usami, Sevak Amtablian, Alain Fave, Mustapha Lemiti, Chiaya Yamamoto, Kiyokazu Nakagawa
Journal of Materials Science and Chemical Engineering (MSCE) , 2017, DOI: 10.4236/msce.2017.51004
Abstract:
Strain-relaxed SiGe is an attractive material for use as a substrate of strained Si, in which carrier mobility is higher than that of bulk Si. The concept of this study is the use of porous Si as a sponge like substrate so that a SiGe lattice can relax without introducing dislocations. We produced porous Si specimens by electrochemical anodization and annealed them under a H2 atmosphere. Then, SiGe thin films were grown by gas-source molecular beam epitaxy. We observed the microstructure of the specimens using transmission electron microscopy. The result showed that we succeeded in producing a single-crys- tal continuous Si0.73Ge0.27 film with a 10% relaxation ratio and a low dislocation density on porous Si.
Reduction of Dislocation Densities of Ge Layers Grown on Si Substrates by Using Microwave Plasma Heating and Fabrication of High Hole Mobility MOSFETs on Ge Layers  [PDF]
Hiroki Nakaie, Tetsuji Arai, Chiaya Yamamoto, Keisuke Arimoto, Junji Yamanaka, Kiyokazu Nakagawa, Toshiyuki Takamatsu
Journal of Materials Science and Chemical Engineering (MSCE) , 2017, DOI: 10.4236/msce.2017.51006
Abstract:
We have developed a microwave plasma heating technique to rapidly heat the transition metal. W/SiO2 layers were deposited on Ge/Si heterostructures. By heating the W, dislocations in Ge layers originated from lattice mismatch between Ge and Si crystals were reduced drastically. We have fabricated p- MOSFETs on Ge/Si substrates and realized higher mobility of about 380 cm2/ Vs than that of Si p-MOSFET.
STEM Moiré Observation of Lattice-Relaxed Germanium Grown on Silicon  [PDF]
Junji Yamanaka, Chiaya Yamamoto, Hiroki Nakaie, Tetsuji Arai, Keisuke Arimoto, Kosuke O. Hara, Kiyokazu Nakagawa
Journal of Materials Science and Chemical Engineering (MSCE) , 2017, DOI: 10.4236/msce.2017.51014
Abstract:
We deposited Ge films on Si substrates by molecular beam epitaxy (MBE) method. The specimens were annealed at around 750 C using microwave- plasma heating technique which we had reported before. After these pro- cesses, we carried out special scanning transmission electron microscopic (STEM) observation. The moiré between the crystal lattices and the scanning lines controlled by STEM was utilized to show lattice-spacing distribution. The results exhibited that we were succeeded in forming lattice-relaxed Ge thin films. It was also recognized that this STEM moiré technique is very useful to observe lattice-spacing distribution for large area with high resolution.
Formation of Poly-Si Films on Glass Substrates by Using Microwave Plasma Heating and Fabrication of TFT’s on the Films  [PDF]
Hiroki Nakaie, Tetsuji Arai, Keisuke Arimoto, Junji Yamanaka, Kiyokazu Nakagawa, Kazuki Kamimura, Toshiyuki Takamatsu
Journal of Materials Science and Chemical Engineering (MSCE) , 2018, DOI: 10.4236/msce.2018.61003
Abstract:
We have developed an apparatus for producing high-density hydrogen plasma. The atomic hydrogen density was 3.0 × 1021 m?3 at a pressure of 30 Pa, a microwave power of 1000 W, and a hydrogen gas flow rate of 5 sccm. We confirmed that the temperatures of tungsten films increased to above 1000?C within 5 s when they were exposed to hydrogen plasma formed using the apparatus. We applied this phenomenon to the selective heat treatment of tungsten films deposited on amorphous silicon films on glass substrates and formed polycrystalline silicon films. To utilize this method, we can perform the crystalline process only on device regions. TFTs were fabricated on the polycrystalline silicon films and the electron mobilities of 60 cm2/Vs were obtained.
TEM Observation of Si0.99C0.01 Thin Films with Arsenic-Ion-, Boron-Ion-, and Silicon-Ion-Implantation Followed by Rapid Thermal Annealing  [PDF]
Junji Yamanaka, Shigenori Inoue, Keisuke Arimoto, Kiyokazu Nakagawa, Kentarou Sawano, Yasuhiro Shiraki, Atsushi Moriya, Yasuhiro Inokuchi, Yasuo Kunii
Journal of Materials Science and Chemical Engineering (MSCE) , 2017, DOI: 10.4236/msce.2017.51003
Abstract:
Strained Si and its related materials, such as strained SiGe and strained silicon-carbon alloy (Si-C), are receiving tremendous interest due to their high carrier mobility. In this study we carry out a basic investigation of the change in microstructure of ion-implanted Si-C solid solution caused by rapid thermal annealing, because it is very important to realize a field-effect transistor made of this new material. The microstructures of arsenic-ion-, boron-ion-, and silicon-ion-implanted Si0.99C0.01 specimens upon thermal annealing are observed using transmission electron microscopy, and it is revealed that the rate of solid-state crystallization of ion-implanted Si-C is slower than that of the ion-implanted Si.
Surface Roughness of SiGe/Si(110) Formed by Stress-Induced Twins and the Solution to Produce Smooth Surface  [PDF]
Junji Yamanaka, Mai Shirakura, Chiaya Yamamoto, Naoto Utsuyama, Kei Sato, Takane Yamada, Kosuke O. Hara, Keisuke Arimoto, Kiyokazu Nakagawa
Journal of Materials Science and Chemical Engineering (MSCE) , 2018, DOI: 10.4236/msce.2018.61004
Abstract:
Lattice-strained Si thin films grown onto SiGe(110)/Si(110) are attracting because of their potential to realize high-speed transistors. In this study we observe surface morphology of Si/SiGe/Si(110) using scanning electron microscopy and we also observe microstructure of the identical position using cross-sectional transmission electron microscopy. These results reveal that crossing of stress-induced twins causes remarkable surface roughness. We propose using vicinal substrate to avoid this phenomenon and our successive experimental results are shown in this paper.
Ohmic Contact Formation for n+4H-SiC Substrate by Selective Heating Method Using Hydrogen Radical Irradiation  [PDF]
Tetsuji Arai, Kazuki Kamimura, Chiaya Yamamoto, Mai Shirakura, Keisuke Arimoto, Junji Yamanaka, Kiyokazu Nakagawa, Toshiyuki Takamatsu, Masaaki Ogino, Masaaki Tachioka, Haruo Nakazawa
Journal of Materials Science and Chemical Engineering (MSCE) , 2017, DOI: 10.4236/msce.2017.51005
Abstract:
We developed an apparatus for producing high-density hydrogen plasma. We confirmed that the temperatures of transition-metal films increased to above 800?C within 5 s when they were exposed to hydrogen plasma formed using the apparatus. We applied this phenomenon to the selective heat treatment of W/Ni films deposited on n+4H-SiC wafers and formed nickel silicide electrodes. To utilize this method, we can perform the nickel silicidation process without heating the other areas such as channel regions and improve the reliability.
Asset Pricing with Stochastic Habit Formation  [PDF]
Masao Nakagawa
Journal of Mathematical Finance (JMF) , 2012, DOI: 10.4236/jmf.2012.22018
Abstract: This paper examines optimal consumption/portfolio choices under stochastic habit formation in which it is uncertain how deep consumers would become in the habit of consuming in future. By extending Shroder and Skiadas [1] to stochastic habit formation, the optimization problem with stochastic habit forming preferences is transformed into that with simple time-additive preferences. Optimal portfolios are composed of the tangency portfolio and habit hedging portfolio. Resulting risk premia are characterized by consumption beta, which is proportionate to the covariance with consumption changes, and habit beta, defined by using the covariance with habit.
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