The Experts below are selected from a list of 108 Experts worldwide ranked by ideXlab platform
Tsukasa Hirayama - One of the best experts on this subject based on the ideXlab platform.
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Accurate measurement of electric potentials in biased Gaas Compound semiconductors by phase-shifting electron holography
Microscopy (Oxford England), 2018Co-Authors: Satoshi Anada, Kazuo Yamamoto, Hirokazu Sasaki, Naoya Shibata, Miko Matsumoto, Yujin Hori, Kouhei Kinugawa, Akihiro Imamura, Tsukasa HirayamaAbstract:The innate electric potentials in biased p- and n-type Gaas Compound semiconductors and the built-in potential were successfully measured with high accuracy and precision by applying in situ phase-shifting electron holography to a wedge-shaped Gaas specimen. A cryo-focused-ion-beam system was used to prepare the 35°-wedge-shaped specimen with smooth surfaces for a precise measurement. The specimen was biased in a transmission electron microscope, and holograms with high-contrast interference fringes were recorded for the phase-shifting method. A clear phase image around the p-n junction was reconstructed even in a thick region (thickness of ~700 nm) at a spatial resolution of 1 nm and precision of 0.01 rad. The innate electric potentials of the unbiased p- and n-type layers were measured to be 12.96 ± 0.17 V and 14.43 ± 0.19 V, respectively. The built-in potential was determined to be 1.48 ± 0.02 V. In addition, the in situ biasing measurement revealed that the measured electric-potential difference between the p and n regions changed by an amount equal to the voltage applied to the specimen, which indicates that all of the external voltage was applied to the p-n junction and that no voltage loss occurred at the other regions.
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direct observation of dopant distribution in Gaas Compound semiconductors using phase shifting electron holography and lorentz microscopy
Journal of Electron Microscopy, 2014Co-Authors: Hirokazu Sasaki, Kazuo Yamamoto, Shinya Otomo, Ryuichiro Minato, Tsukasa HirayamaAbstract:Phase-shifting electron holography and Lorentz microscopy were used to map dopant distributions in Gaas Compound semiconductors with step-like dopant concentration. Transmission electron microscope specimens were prepared using a triple beam focused ion beam (FIB) system, which combines a Ga ion beam, a scanning electron microscope, and an Ar ion beam to remove the FIB damaged layers. The p–n junctions were clearly observed in both under-focused and over-focused Lorentz microscopy images. A phase image was obtained by using a phase-shifting reconstruction method to simultaneously achieve high sensitivity and high spatial resolution. Differences in dopant concentrations between 1 × 10 19 cm –3 and 1 × 10 18 cm –3 regions were clearly observed by using phaseshifting electron holography. We also interpreted phase profiles quantitatively by considering inactive layers induced by ion implantation during the FIB process. The thickness of an inactive layer at different dopant concentration area can be measured from the phase image.
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Development of advanced electron holographic techniques and application to industrial materials and devices.
Microscopy (Oxford England), 2013Co-Authors: Kazuo Yamamoto, Tsukasa Hirayama, Takayoshi TanjiAbstract:The development of a transmission electron microscope equipped with a field emission gun paved the way for electron holography to be put to practical use in various fields. In this paper, we review three advanced electron holography techniques: on-line real-time electron holography, three-dimensional (3D) tomographic holography and phase-shifting electron holography, which are becoming important techniques for materials science and device engineering. We also describe some applications of electron holography to the analysis of industrial materials and devices: Gaas Compound semiconductors, solid oxide fuel cells and all-solid-state lithium ion batteries.
Kazuo Yamamoto - One of the best experts on this subject based on the ideXlab platform.
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Accurate measurement of electric potentials in biased Gaas Compound semiconductors by phase-shifting electron holography
Microscopy (Oxford England), 2018Co-Authors: Satoshi Anada, Kazuo Yamamoto, Hirokazu Sasaki, Naoya Shibata, Miko Matsumoto, Yujin Hori, Kouhei Kinugawa, Akihiro Imamura, Tsukasa HirayamaAbstract:The innate electric potentials in biased p- and n-type Gaas Compound semiconductors and the built-in potential were successfully measured with high accuracy and precision by applying in situ phase-shifting electron holography to a wedge-shaped Gaas specimen. A cryo-focused-ion-beam system was used to prepare the 35°-wedge-shaped specimen with smooth surfaces for a precise measurement. The specimen was biased in a transmission electron microscope, and holograms with high-contrast interference fringes were recorded for the phase-shifting method. A clear phase image around the p-n junction was reconstructed even in a thick region (thickness of ~700 nm) at a spatial resolution of 1 nm and precision of 0.01 rad. The innate electric potentials of the unbiased p- and n-type layers were measured to be 12.96 ± 0.17 V and 14.43 ± 0.19 V, respectively. The built-in potential was determined to be 1.48 ± 0.02 V. In addition, the in situ biasing measurement revealed that the measured electric-potential difference between the p and n regions changed by an amount equal to the voltage applied to the specimen, which indicates that all of the external voltage was applied to the p-n junction and that no voltage loss occurred at the other regions.
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direct observation of dopant distribution in Gaas Compound semiconductors using phase shifting electron holography and lorentz microscopy
Journal of Electron Microscopy, 2014Co-Authors: Hirokazu Sasaki, Kazuo Yamamoto, Shinya Otomo, Ryuichiro Minato, Tsukasa HirayamaAbstract:Phase-shifting electron holography and Lorentz microscopy were used to map dopant distributions in Gaas Compound semiconductors with step-like dopant concentration. Transmission electron microscope specimens were prepared using a triple beam focused ion beam (FIB) system, which combines a Ga ion beam, a scanning electron microscope, and an Ar ion beam to remove the FIB damaged layers. The p–n junctions were clearly observed in both under-focused and over-focused Lorentz microscopy images. A phase image was obtained by using a phase-shifting reconstruction method to simultaneously achieve high sensitivity and high spatial resolution. Differences in dopant concentrations between 1 × 10 19 cm –3 and 1 × 10 18 cm –3 regions were clearly observed by using phaseshifting electron holography. We also interpreted phase profiles quantitatively by considering inactive layers induced by ion implantation during the FIB process. The thickness of an inactive layer at different dopant concentration area can be measured from the phase image.
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Development of advanced electron holographic techniques and application to industrial materials and devices.
Microscopy (Oxford England), 2013Co-Authors: Kazuo Yamamoto, Tsukasa Hirayama, Takayoshi TanjiAbstract:The development of a transmission electron microscope equipped with a field emission gun paved the way for electron holography to be put to practical use in various fields. In this paper, we review three advanced electron holography techniques: on-line real-time electron holography, three-dimensional (3D) tomographic holography and phase-shifting electron holography, which are becoming important techniques for materials science and device engineering. We also describe some applications of electron holography to the analysis of industrial materials and devices: Gaas Compound semiconductors, solid oxide fuel cells and all-solid-state lithium ion batteries.
Hirokazu Sasaki - One of the best experts on this subject based on the ideXlab platform.
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Accurate measurement of electric potentials in biased Gaas Compound semiconductors by phase-shifting electron holography
Microscopy (Oxford England), 2018Co-Authors: Satoshi Anada, Kazuo Yamamoto, Hirokazu Sasaki, Naoya Shibata, Miko Matsumoto, Yujin Hori, Kouhei Kinugawa, Akihiro Imamura, Tsukasa HirayamaAbstract:The innate electric potentials in biased p- and n-type Gaas Compound semiconductors and the built-in potential were successfully measured with high accuracy and precision by applying in situ phase-shifting electron holography to a wedge-shaped Gaas specimen. A cryo-focused-ion-beam system was used to prepare the 35°-wedge-shaped specimen with smooth surfaces for a precise measurement. The specimen was biased in a transmission electron microscope, and holograms with high-contrast interference fringes were recorded for the phase-shifting method. A clear phase image around the p-n junction was reconstructed even in a thick region (thickness of ~700 nm) at a spatial resolution of 1 nm and precision of 0.01 rad. The innate electric potentials of the unbiased p- and n-type layers were measured to be 12.96 ± 0.17 V and 14.43 ± 0.19 V, respectively. The built-in potential was determined to be 1.48 ± 0.02 V. In addition, the in situ biasing measurement revealed that the measured electric-potential difference between the p and n regions changed by an amount equal to the voltage applied to the specimen, which indicates that all of the external voltage was applied to the p-n junction and that no voltage loss occurred at the other regions.
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Imaging of built-in electric field at a p-n junction by scanning transmission electron microscopy
Scientific Reports, 2015Co-Authors: Naoya Shibata, Hirokazu Sasaki, Shinya Otomo, Ryuichiro Minato, Scott D. Findlay, Takao Matsumoto, Hidetaka Sawada, Yuji Kohno, Yuichi IkuharaAbstract:Precise measurement and characterization of electrostatic potential structures and the concomitant electric fields at nanodimensions are essential to understand and control the properties of modern materials and devices. However, directly observing and measuring such local electric field information is still a major challenge in microscopy. Here, differential phase contrast imaging in scanning transmission electron microscopy with segmented type detector is used to image a p-n junction in a Gaas Compound semiconductor. Differential phase contrast imaging is able to both clearly visualize and quantify the projected, built-in electric field in the p-n junction. The technique is further shown capable of sensitively detecting the electric field variations due to dopant concentration steps within both p -type and n -type regions. Through live differential phase contrast imaging, this technique can potentially be used to image the electromagnetic field structure of new materials and devices even under working conditions.
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direct observation of dopant distribution in Gaas Compound semiconductors using phase shifting electron holography and lorentz microscopy
Journal of Electron Microscopy, 2014Co-Authors: Hirokazu Sasaki, Kazuo Yamamoto, Shinya Otomo, Ryuichiro Minato, Tsukasa HirayamaAbstract:Phase-shifting electron holography and Lorentz microscopy were used to map dopant distributions in Gaas Compound semiconductors with step-like dopant concentration. Transmission electron microscope specimens were prepared using a triple beam focused ion beam (FIB) system, which combines a Ga ion beam, a scanning electron microscope, and an Ar ion beam to remove the FIB damaged layers. The p–n junctions were clearly observed in both under-focused and over-focused Lorentz microscopy images. A phase image was obtained by using a phase-shifting reconstruction method to simultaneously achieve high sensitivity and high spatial resolution. Differences in dopant concentrations between 1 × 10 19 cm –3 and 1 × 10 18 cm –3 regions were clearly observed by using phaseshifting electron holography. We also interpreted phase profiles quantitatively by considering inactive layers induced by ion implantation during the FIB process. The thickness of an inactive layer at different dopant concentration area can be measured from the phase image.
Takayoshi Tanji - One of the best experts on this subject based on the ideXlab platform.
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Development of advanced electron holographic techniques and application to industrial materials and devices.
Microscopy (Oxford England), 2013Co-Authors: Kazuo Yamamoto, Tsukasa Hirayama, Takayoshi TanjiAbstract:The development of a transmission electron microscope equipped with a field emission gun paved the way for electron holography to be put to practical use in various fields. In this paper, we review three advanced electron holography techniques: on-line real-time electron holography, three-dimensional (3D) tomographic holography and phase-shifting electron holography, which are becoming important techniques for materials science and device engineering. We also describe some applications of electron holography to the analysis of industrial materials and devices: Gaas Compound semiconductors, solid oxide fuel cells and all-solid-state lithium ion batteries.
James F Christian - One of the best experts on this subject based on the ideXlab platform.
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Development of Photodiodes for Use in Wide Band-Gap Solid-State Photomultipliers
IEEE Transactions on Nuclear Science, 2013Co-Authors: Michael D. Hammig, Taehoon Kang, Wenlu Sun, Xiao-jie Chen, Erik Johnson, Kyusang Lee, Joe C. Campbell, James F ChristianAbstract:To address the limitations of existing silicon solid-state photomultipliers (SSPMs), we are developing new photodetector elements in Al0.8Ga0.2As . With 80% aluminum concentration in the Gaas Compound, the material effectively becomes a wide band-gap semiconductor with a band-gap energy of ~2.1 eV. The wide band-gap characteristic and the relative maturity of Gaas material processing makes Al0.8Ga0.2As an excellent material for developing improved SSPMs with lower dark current. Materials with larger band gaps have a lower limit in the associated thermally generated dark current. With a proper device structure, the AlGaas SSPM is expected to provide a smaller dark current with high detection efficiency within the blue to UV spectral region, which is ideal for state-of-the-art scintillation materials, such as LaBr , CeBr , and CLYC that emit in the UV region. Utilizing commercially grown AlGaas epitaxial wafers as the starting material, prototype photodiode elements have been designed and fabricated. The photodiodes, which have a mesa structure, exhibit a 20-30-V reverse bias breakdown. This work presents the fabrication and characterization of prototype avalanche photodiodes. Geiger pulses induced by both thermal electrons and photons are also presented, and the photon detection efficiency at low excess bias is estimated.
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Development of ${\hbox{Al}}_{\scriptscriptstyle 0.8} {\hbox{Ga}}_{\scriptscriptstyle 0.2}{\hbox{As}}$ Photodiodes for Use in Wide Band-Gap Solid-State Photomultipliers
IEEE Transactions on Nuclear Science, 2013Co-Authors: Michael D. Hammig, Taehoon Kang, Wenlu Sun, Xiao-jie Chen, Kyusang Lee, Joe C. Campbell, Erik B. Johnson, James F ChristianAbstract:To address the limitations of existing silicon solid-state photomultipliers (SSPMs), we are developing new photodetector elements in Al0.8Ga0.2As . With 80% aluminum concentration in the Gaas Compound, the material effectively becomes a wide band-gap semiconductor with a band-gap energy of ~2.1 eV. The wide band-gap characteristic and the relative maturity of Gaas material processing makes Al0.8Ga0.2As an excellent material for developing improved SSPMs with lower dark current. Materials with larger band gaps have a lower limit in the associated thermally generated dark current. With a proper device structure, the AlGaas SSPM is expected to provide a smaller dark current with high detection efficiency within the blue to UV spectral region, which is ideal for state-of-the-art scintillation materials, such as LaBr , CeBr , and CLYC that emit in the UV region. Utilizing commercially grown AlGaas epitaxial wafers as the starting material, prototype photodiode elements have been designed and fabricated. The photodiodes, which have a mesa structure, exhibit a 20-30-V reverse bias breakdown. This work presents the fabrication and characterization of prototype avalanche photodiodes. Geiger pulses induced by both thermal electrons and photons are also presented, and the photon detection efficiency at low excess bias is estimated.
