Patents by Inventor Akira Yoshikawa
Akira Yoshikawa has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).
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Patent number: 11939504Abstract: The present invention aims to provide a scintillator which has a short fluorescence decay time, whose fluorescence intensity after a period of time following radiation irradiation is low, and which shows largely improved light-transmittance. A scintillator represented by the following General Formula (1), the scintillator including Zr, having a Zr content of not less than 1500 ppm by mass therein, and being a block of a sintered body. QxMyO3z:A . . . (1) (wherein in General Formula (1), Q includes at least one or more kinds of divalent metallic elements; M includes at least Hf; and x, y, and z independently satisfy 0.5?x?1.5, 0.5?y?1.5, and 0.7?z?1.5, respectively).Type: GrantFiled: June 23, 2022Date of Patent: March 26, 2024Assignee: Mitsubishi Chemical CorporationInventors: Koji Hazu, Kentaro Horibe, Tetsuya Kawano, Keiji Yamahara, Shunsuke Kurosawa, Akira Yoshikawa
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Publication number: 20240097671Abstract: A semiconductor device includes a first transistor, a first drive circuit including a second transistor, and a second drive circuit including a third transistor. The second transistor and the third transistor are connected in series; and a connection node of the second and third transistors is connected to a gate electrode of the first transistor. The first transistor, the second transistor, and the third transistor are normally-off MOS HEMTs formed in a first substrate that includes GaN. The first drive circuit charges a parasitic capacitance of the first transistor. The second drive circuit discharges the parasitic capacitance of the first transistor.Type: ApplicationFiled: February 10, 2023Publication date: March 21, 2024Inventors: Toru SUGIYAMA, Noriaki YOSHIKAWA, Yasuhiko KURIYAMA, Akira YOSHIOKA, Hitoshi KOBAYASHI, Hung HUNG, Yasuhiro ISOBE, Tetsuya OHNO, Hideki SEKIGUCHI, Masaaki ONOMURA
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Publication number: 20240019592Abstract: A scintillator, having a composition represented by the following general formula (1), including a substitution element A, the substitution element A comprising at least La, and a total molar content of the substitution element A being 0.00001 mol or more and 0.05 mol or less in 1 mol of the scintillator, and further including an activator element B, the activator element B being constituted from Ce, having a perovskite-type crystal structure, and exhibiting a linear transmittance of light at a wavelength of 800 nm, at a thickness of 1.9 mm, of 30% or more. QMxO3y . . . (1): wherein Q represents one or more elements selected from the group consisting of Ca, Sr and Ba; M represents Hf; Q and M are each optionally substituted with other element at a proportion of 20% by mol or less; and x and y respectively satisfy 0.5?x?1.5 and 0.7?y?1.5.Type: ApplicationFiled: September 26, 2023Publication date: January 18, 2024Applicants: Mitsubishi Chemical Corporation, TOHOKU UNIVERSITYInventors: Koji Hazu, Keiji Yamahara, Shunsuke Kurosawa, Akira Yoshikawa
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Publication number: 20230218249Abstract: The signal processing system generates image data, based on an electric signal group output from a radiation detector, and recognizes the electric signal group as a processing target, and the electric signal group includes at least part of an electric signal group meeting the following requirements: the electric signal group is an electric signal group with a signal value within a predetermined range, the electric signal group corresponding to a gamma ray with energy equal to or less than 375 keV; the predetermined range is equal to or greater than 50% and equal to or less than 80% relative to a 100% signal value; and the 100% signal value is a signal value detected when a gamma ray with energy of 511 keV enters a radiation detection element in the radiation detector and is totally absorbed by the radiation detection element.Type: ApplicationFiled: March 8, 2023Publication date: July 13, 2023Applicants: Mitsubishi Chemical Corporation, Tohoku UniversityInventors: Koji Hazu, Kentaro Horibe, Keiji Yamahara, Shunsuke Kurosawa, Akira Yoshikawa
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Patent number: 11637221Abstract: To provide a nitride semiconductor element having a better contact resistance reduction effect also in the case of a light emitting element containing AlGaN having a high Al composition. The nitride semiconductor element has a substrate 1, a first conductivity type first nitride semiconductor layer 2 formed on the substrate 1, and a first electrode layer 4 formed on the first nitride semiconductor layer 2. The first electrode layer 4 contains aluminum and nickel, and both aluminum and an alloy containing aluminum and nickel are present in a contact surface to the first nitride semiconductor layer 2 or in the vicinity of the contact surface.Type: GrantFiled: December 24, 2020Date of Patent: April 25, 2023Assignee: ASAHI KASEI KABUSHIKI KAISHAInventors: Aya Yokoyama, Yoshihito Hagihara, Ryosuke Hasegawa, Akira Yoshikawa, Ziyi Zhang, Tomohiro Morishita
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Publication number: 20220363987Abstract: An object of the present invention is to provide a scintillator having a high radiation stopping power, and having a shorter fluorescence decay time compared to conventional scintillators. The above object is achieved by setting the composition of a scintillator to a composition represented by General Formula (1). QxMyO3z??(1) (wherein in General Formula (1), Q includes at least two or more divalent metallic elements; M includes at least Hf; and x, y, and z independently satisfy 0.5?x?1.5, 0.5?y?1.5, and 0.7?z?1.5, respectively).Type: ApplicationFiled: July 19, 2022Publication date: November 17, 2022Applicants: Mitsubishi Chemical Corporation, Tohoku UniversityInventors: Koji Hazu, Kentaro Horibe, Keiji Yamahara, Sunsuke Kurosawa, Akira Yoshikawa
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Publication number: 20220326400Abstract: The present invention aims to provide a scintillator which has a short fluorescence decay time, whose fluorescence intensity after a period of time following radiation irradiation is low, and which shows largely improved light-transmittance. A scintillator represented by the following General Formula (1), the scintillator including Zr, having a Zr content of not less than 1500 ppm by mass therein, and being a block of a sintered body. QxMyO3z:A . . . (1) (wherein in General Formula (1), Q includes at least one or more kinds of divalent metallic elements; M includes at least Hf; and x, y, and z independently satisfy 0.5?x?1.5, 0.5?y?1.5, and 0.7?z?1.5, respectively).Type: ApplicationFiled: June 23, 2022Publication date: October 13, 2022Applicants: Mitsubishi Chemical Corporation, Tohoku UniversityInventors: Koji Hazu, Kentaro Horibe, Tetsuya Kawano, Keiji Yamahara, Shunsuke Kurosawa, Akira Yoshikawa
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Patent number: 11158784Abstract: The present invention makes clear and defines a congruent composition of a langasite-based oxide, and establishes a method of manufacturing a crystal by any desired composition of AE3ME1+a(Ga1?xAlx)3+bSi2+cO14 (AE is an alkaline-earth metal, ME is Nb or Ta, 0?x?1, ?0.5<a?0 or 0<a<0.5, ?0.5<b?0 or 0<b?0.5, and ?0.5<c?0 or 0<c<0.5, excluding a=b=c=0). This makes it possible to suppress the formation of an impurity, and improve the yield and crystal manufacturing rate. The raw material is a raw material mixture prepared by mixing an alkaline-earth metal or its carbonate or oxide, Nb or Ta or its oxide, Ga or its oxide, Al or its oxide, and Si or its oxide.Type: GrantFiled: February 24, 2017Date of Patent: October 26, 2021Assignees: PIEZO STUDIO INC., TOHOKU UNIVERSITYInventors: Akira Yoshikawa, Yuui Yokota, Yuji Ohashi, Kei Kamada, Tetsuo Kudo, Kenji Inoue, Yasuhiro Shoji, Yu Igarashi, Mototaka Arakawa, Shunsuke Kurosawa, Akihiro Yamaji
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Publication number: 20210277504Abstract: A metal member according to this invention is composed of polycrystals of a metal made of ruthenium or an alloy containing ruthenium at a maximum ratio. The aspect ratio of a crystal grain of the polycrystalline metal member is 1.5 or more. A plurality of crystal grains forming the metal member are arranged with their major axes being pointed in the same direction, and the number of crystal grains in a section in the major axis direction of the crystal grains is 120 or less per 1 mm2.Type: ApplicationFiled: June 27, 2018Publication date: September 9, 2021Inventors: Akira YOSHIKAWA, Rikito MURAKAMI, Yui YOKOTA, Takayuki NIHEI, Kei KAMADA, Yasuhiro SHOJI, Shunsuke KUROSAWA, Akihiro YAMAJI, Yuji OHASHI
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Patent number: 11031539Abstract: To provide a vibrator made of a piezoelectric crystal having a larger electromechanical coupling coefficient and a more satisfactory frequency-temperature characteristic than those of quartz, a vibrating piece (101) is made of a Ca3Ta(Ga1-xAlx)3Si2O14 single crystal (0<x?1). In the single crystal, letting ? be a rotation angle from an X-Z plane about an X-axis serving as a rotation axis, 18x+17.5???24x+24.5 is set. In addition, the vibrating piece (101) is made of a Ca3Nb(Ga1-xAlx)3Si2O14 single crystal (0<x?1). In the single crystal of this arrangement, letting ? be a rotation angle from an X-Z plane about an X-axis serving as a rotation axis, 25x+23.083???32x+26.167 is set.Type: GrantFiled: November 4, 2016Date of Patent: June 8, 2021Assignees: PIEZO STUDIO INC., TOHOKU UNIVERSITYInventors: Akira Yoshikawa, Yuji Ohashi, Yuui Yokota, Kei Kamada, Masatoshi Ito, Kenji Inoue, Hiroyuki Amano
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Publication number: 20210119083Abstract: To provide a nitride semiconductor element having a better contact resistance reduction effect also in the case of a light emitting element containing AlGaN having a high Al composition. The nitride semiconductor element has a substrate 1, a first conductivity type first nitride semiconductor layer 2 formed on the substrate 1, and a first electrode layer 4 formed on the first nitride semiconductor layer 2. The first electrode layer 4 contains aluminum and nickel, and both aluminum and an alloy containing aluminum and nickel are present in a contact surface to the first nitride semiconductor layer 2 or in the vicinity of the contact surface.Type: ApplicationFiled: December 24, 2020Publication date: April 22, 2021Inventors: Aya YOKOYAMA, Yoshihito HAGIHARA, Ryosuke HASEGAWA, Akira YOSHIKAWA, Ziyi ZHANG, Tomohiro MORISHITA
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Patent number: 10937928Abstract: To provide a nitride semiconductor element having a better contact resistance reduction effect also in the case of a light emitting element containing AlGaN having a high Al composition. The nitride semiconductor element has a substrate 1, a first conductivity type first nitride semiconductor layer 2 formed on the substrate 1, and a first electrode layer 4 formed on the first nitride semiconductor layer 2. The first electrode layer 4 contains aluminum and nickel, and both aluminum and an alloy containing aluminum and nickel are present in a contact surface to the first nitride semiconductor layer 2 or in the vicinity of the contact surface.Type: GrantFiled: November 8, 2018Date of Patent: March 2, 2021Assignee: ASAHI KASEI KABUSHIKI KAISHAInventors: Aya Yokoyama, Yoshihito Hagihara, Ryosuke Hasegawa, Akira Yoshikawa, Ziyi Zhang, Tomohiro Morishita
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Patent number: 10771032Abstract: To improve the Q value of a piezoelectric thin-film element in a state in which unnecessary vibration is suppressed, an acoustic reflection film (104) is affixed to a first electrode (102), a piezoelectric single-crystal substrate (101) is thinned by polishing from the other surface (101b) of the piezoelectric single-crystal substrate (101), such that the first electrode (102) and piezoelectric thin film (105) are piled on the piezoelectric single-crystal substrate (101). In this polishing, a pressure (polishing pressure) to the surface (101b) during polishing in an electrode formation region where the first electrode (102) is formed differs from that in a non-electrode formation region around the electrode formation region. Consequently, the electrode formation region of the piezoelectric thin film (105), where the first electrode (102) is formed, is made thinner than the non-electrode formation region around the electrode formation region.Type: GrantFiled: July 25, 2016Date of Patent: September 8, 2020Assignees: PIEZO STUDIO INC., TOHOKU UNIVERSITYInventors: Kenji Inoue, Akira Yoshikawa, Yuji Ohashi, Yuui Yokota, Kei Kamada, Shunsuke Kurosawa
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Patent number: 10734225Abstract: A nitride semiconductor substrate includes a sapphire substrate and a nitride semiconductor layer formed thereon and containing a group III element including Al and nitrogen as a main component. A surface of the sapphire substrate where the nitride semiconductor layer is formed includes recesses having a maximum opening size of from 2 nm to 60 nm in an amount of from 1×109 pieces to 1×1011 pieces per cm2. The recesses and surfaces immediately above the recesses form spaces. Of a surface of the nitride semiconductor layer on the sapphire substrate side, a height difference ?H between a surface immediately above of each recess and a surface in contact with a flat surface is 10 nm or less. A portion of the nitride semiconductor layer above each recess has a crystalline structure produced by growth along a polar plane of the group III element.Type: GrantFiled: November 8, 2017Date of Patent: August 4, 2020Assignee: ASAHI KASEI KABUSHIKI KAISHAInventors: Akira Yoshikawa, Tomohiro Morishita, Motoaki Iwaya
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Publication number: 20190355571Abstract: A nitride semiconductor substrate includes a sapphire substrate and a nitride semiconductor layer formed thereon and containing a group III element including Al and nitrogen as a main component. A surface of the sapphire substrate where the nitride semiconductor layer is formed includes recesses having a maximum opening size of from 2 nm to 60 nm in an amount of from 1×109 pieces to 1×1011 pieces per cm2. The recesses and surfaces immediately above the recesses form spaces. Of a surface of the nitride semiconductor layer on the sapphire substrate side, a height difference ?H between a surface immediately above of each recess and a surface in contact with a flat surface is 10 nm or less. A portion of the nitride semiconductor layer above each recess has a crystalline structure produced by growth along a polar plane of the group III element.Type: ApplicationFiled: November 8, 2017Publication date: November 21, 2019Applicants: ASAHI KASEI KABUSHIKI KAISHA, MEIJO UNIVERSITYInventors: Akira Yoshikawa, Tomohiro Morishita, Motoaki Iwaya
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Patent number: 10424684Abstract: An MSM ultraviolet ray receiving element has a low dark state current value and a good photosensitivity. The MSM ultraviolet ray receiving element has a first nitride semiconductor layer on a substrate, a second nitride semiconductor layer on the first nitride semiconductor layer, and first and second electrodes on the second nitride semiconductor layer. The first nitride semiconductor layer contains AlXGa(1-X)N (0.4?X?0.90). The second nitride semiconductor layer contains AlYGa(1-Y)N with a film thickness t (nm) satisfying 5?t?25. The first electrode and the second electrode contain a material containing at least three elements of Ti, Al, Au, Ni, V, Mo, Hf, Ta, W, Nb, Zn, Ag, Cr, and Zr. Al composition ratios X and Y and a film thickness t satisfy ?0.009×t+X+0.22?0.03?Y??0.009×t+X+0.22+0.03.Type: GrantFiled: June 8, 2018Date of Patent: September 24, 2019Assignee: ASAHI KASEI KABUSHIKI KAISHAInventors: Akira Yoshikawa, Kazuhiro Nagase, Motoaki Iwaya, Saki Ushida
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Publication number: 20190140160Abstract: The present invention makes clear and defines a congruent composition of a langasite-based oxide, and establishes a method of manufacturing a crystal by any desired composition of AE3ME1+a(Ga1-xAlx)3+bSi2+cO14 (AE is an alkaline-earth metal, ME is Nb or Ta, 0?x?1, ?0.5<a?0 or 0<a<0.5, ?0.5<b?0 or 0<b?0.5, and ?0.5<c?0 or 0<c<0.5, excluding a=b=c=0). This makes it possible to suppress the formation of an impurity, and improve the yield and crystal manufacturing rate. The raw material is a raw material mixture prepared by mixing an alkaline-earth metal or its carbonate or oxide, Nb or Ta or its oxide, Ga or its oxide, Al or its oxide, and Si or its oxide.Type: ApplicationFiled: February 24, 2017Publication date: May 9, 2019Inventors: Akira YOSHIKAWA, Yuui YOKOTA, Yuji OHASHI, Kei KAMADA, Tetsuo KUDO, Kenji INOUE, Yasuhiro SHOJI, Yu IGARASHI, Mototaka ARAKAWA, Shunsuke KUROSAWA, Akihiro YAMAJI
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Publication number: 20190140141Abstract: To provide a nitride semiconductor element having a better contact resistance reduction effect also in the case of a light emitting element containing AlGaN having a high Al composition. The nitride semiconductor element has a substrate 1, a first conductivity type first nitride semiconductor layer 2 formed on the substrate 1, and a first electrode layer 4 formed on the first nitride semiconductor layer 2. The first electrode layer 4 contains aluminum and nickel, and both aluminum and an alloy containing aluminum and nickel are present in a contact surface to the first nitride semiconductor layer 2 or in the vicinity of the contact surface.Type: ApplicationFiled: November 8, 2018Publication date: May 9, 2019Applicant: ASAHI KASEI KABUSHIKI KAISHAInventors: Aya YOKOYAMA, Yoshihito HAGIHARA, Ryosuke HASEGAWA, Akira YOSHIKAWA, Ziyi ZHANG, Tomohiro MORISHITA
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Patent number: 10174247Abstract: An illuminant has a short fluorescence lifetime, high transparency, and high light yield and a radiation detector uses the illuminant. The illuminant is appropriate for a radiation detector for detecting gamma-rays, X-rays, ?-rays, and neutron rays, and has high radiation resistance, a short fluorescence decay time and high emission intensity. The illuminant has a garnet structure using emission from the 4f5d level of Ce3+, and includes a garnet illuminant prepared by co-doping of at least one type of monovalent or divalent cation at a molar ratio of 7000 ppm or less with respect to all cations, to an illuminant having a garnet structure represented by general formula CexRE3?xM5+yO12+3y/2 (where 0.0001?x?0.3, 0?y?0.5 or 0?y??0.5, M is one type or two or more types selected from Al, Lu, Ga, and Sc, and RE is one type or two or more types selected from La, Pr, Gd, Tb, Yb, Y, and Lu).Type: GrantFiled: April 30, 2015Date of Patent: January 8, 2019Assignees: TOHOKU TECHNO ARCH CO., LTD., C & A CORPORATIONInventors: Kei Kamada, Akira Yoshikawa, Yuui Yokota, Shunsuke Kurosawa, Yasuhiro Shoji
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Publication number: 20180358500Abstract: An MSM ultraviolet ray receiving element has a low dark state current value and a good photosensitivity. The MSM ultraviolet ray receiving element has a first nitride semiconductor layer on a substrate, a second nitride semiconductor layer on the first nitride semiconductor layer, and first and second electrodes on the second nitride semiconductor layer. The first nitride semiconductor layer contains AlXGa(1-X)N (0.4?X?0.90). The second nitride semiconductor layer contains AlYGa(1-Y)N with a film thickness t (nm) satisfying 5?t?25. The first electrode and the second electrode contain a material containing at least three elements of Ti, Al, Au, Ni, V, Mo, Hf, Ta, W, Nb, Zn, Ag, Cr, and Zr. Al composition ratios X and Y and a film thickness t satisfy ?0.009×t+X+0.22?0.03?Y??0.009×t+X+0.22+0.03.Type: ApplicationFiled: June 8, 2018Publication date: December 13, 2018Applicant: ASAHI KASEI KABUSHIKI KAISHAInventors: Akira YOSHIKAWA, Kazuhiro NAGASE, Motoaki IWAYA, Saki USHIDA