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27 results on '"Tanaka, Atsunori"'

2. High Density Individually Addressable Nanowire Arrays Record Intracellular Activity from Primary Rodent and Human Stem Cell Derived Neurons

Author

Liu, Ren, Chen, Renjie, Elthakeb, Ahmed T, Lee, Sang Heon, Hinckley, Sandy, Khraiche, Massoud L, Scott, John, Pre, Deborah, Hwang, Yoontae, Tanaka, Atsunori, Ro, Yun Goo, Matsushita, Albert K, Dai, Xing, Soci, Cesare, Biesmans, Steven, James, Anthony, Nogan, John, Jungjohann, Katherine L, Pete, Douglas V, Webb, Denise B, Zou, Yimin, Bang, Anne G, and Dayeh, Shadi A

Published
2017

4. Strong Geometrical Effects in Submillimeter Selective Area Growth and Light Extraction of GaN Light Emitting Diodes on Sapphire.

Author

Tanaka, Atsunori, Chen, Renjie, Jungjohann, Katherine L, and Dayeh, Shadi A

Subjects
Biochemistry and Cell Biology, Other Physical Sciences
Abstract

Advanced semiconductor devices often utilize structural and geometrical effects to tailor their characteristics and improve their performance. We report here detailed understanding of such geometrical effects in the epitaxial selective area growth of GaN on sapphire substrates and utilize them to enhance light extraction from GaN light emitting diodes. Systematic size and spacing effects were performed side-by-side on a single 2" sapphire substrate to minimize experimental sampling errors for a set of 144 pattern arrays with circular mask opening windows in SiO2. We show that the mask opening diameter leads to as much as 4 times increase in the thickness of the grown layers for 20 μm spacings and that spacing effects can lead to as much as 3 times increase in thickness for a 350 μm dot diameter. We observed that the facet evolution in comparison with extracted Ga adatom diffusion lengths directly influences the vertical and lateral overgrowth rates and can be controlled with pattern geometry. Such control over the facet development led to 2.5 times stronger electroluminescence characteristics from well-faceted GaN/InGaN multiple quantum well LEDs compared to non-faceted structures.

Published
2015

5. Heteroepitaxial Thick GaN Layers and Vertical High-Power Devices by Selective Area MOCVD Growth

Author

Tanaka, Atsunori

Subjects
Materials Science, Electrical engineering, Epitaxy, GaN, MOCVD, Power Device, Selective Growth
Abstract

Gallium nitride (GaN) is now widely used in commercial white Light Emitting Diodes (LEDs) thanks to the emergence of high-brightness GaN blue LEDs in 1990s. In addition to its application in solid-state lighting, GaN has been also vowed as a strong contender for next-generation high power and frequency devices due to its high critical electric field (3.3 MV/cm) and high mobility of the 2-dimensional electron gas (2DEG) at the aluminum gallium nitride (AlGaN)/GaN interface. Lateral AlGaN/GaN high-electron-mobility-transistors (HEMTs) have been available as commercial off-the-shelf devices since 2005. However, with the demand for even higher power at reduced chip area and cost and with better thermal management at high currents, vertical device architectures have emerged as the chosen structure to meet these demands. But vertical devices that can hold high power require thick and high quality GaN layers. Recent developments of bulk GaN substrate growth technologies allowed vertical GaN device with thick drift layer to be more feasible. However, GaN substrate technology is challenged with cost, reliability and uniformity issues even at the currently commercially available 2” (diameter) substrates. Therefore, GaN vertical power devices on cheap substrates without compromising the GaN material quality remains to be of great interest. Si substrates with their fab-scale integrated circuit technology can propel the development of commercial vertical high power GaN devices. The biggest challenge for realizing thick GaN layers on Si to hold high voltage in the vertical direction is the large thermal and lattice mismatch between GaN and Si that leads to cracking of the GaN layers beyond only a few micrometers.In major part of this dissertation, we will focus on the epitaxy techniques of thick crack-free GaN layers on Si by selective area growth (SAG) and the fabrication of vertical GaN switches. The epitaxy technique developed in this work resulted in crack-free thick GaN layers on Si that are of high quality with low dislocation densities and low background doping in order to sustain high breakdown voltages. The developed processes hold the potential to significantly advance the fundamental electronic materials research in power devices and their efficient system level integration.

Published
2019

7. Scalable Thousand Channel Penetrating Microneedle Arrays on Flex for Multimodal and Large Area Coverage BrainMachine Interfaces (Adv. Funct. Mater. 25/2022)

Author

Lee, Sang Heon, primary, Thunemann, Martin, additional, Lee, Keundong, additional, Cleary, Daniel R., additional, Tonsfeldt, Karen J., additional, Oh, Hongseok, additional, Azzazy, Farid, additional, Tchoe, Youngbin, additional, Bourhis, Andrew M., additional, Hossain, Lorraine, additional, Ro, Yun Goo, additional, Tanaka, Atsunori, additional, Kılıç, Kıvılcım, additional, Devor, Anna, additional, and Dayeh, Shadi A., additional

Published
2022
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11. Development of a calculation method for atmospheric dispersion database that can immediately provide calculation results for any source term and period from hindcast to short-term forecast (Joint research)

Author

Terada, Hiroaki, Tsuzuki, Katsunori, Kadowaki, Masanao, Nagai, Haruyasu, and Tanaka, Atsunori

Abstract

原子力緊急時の様々な大気拡散予測のニーズに対応するとともに、事前の環境モニタリング等の事故対応計画の策定に有効な情報をデータベースとして整備することが可能な大気拡散計算手法の開発を行った。本手法では、放出源情報のうち放出点以外の放射性核種、放出率、及び放出期間を特定することなく拡散計算を実施してデータベース化しておき、放出源情報を与えた際にその条件に基づく予測結果を即座に得ることが可能である。この計算を気象解析・予報データの更新に合わせて定常的に実行し、過去から数日先までの連続的なデータベースを整備することで、過去解析から短期の将来予測まで任意の期間及び放出源情報に対する計算結果を即座に作成可能である。この機能は、過去の様々な気象条件に対する拡散解析結果の分析により、モニタリング計画の最適化等の事前計画の立案に利用できる。また、様々な仮想放出源情報を用いた拡散解析により、緊急時対策を検討する上で想定すべき事象の把握が可能である。さらに、本手法に基づきモニタリング結果から放出源情報を逆推定して放射性物質の時空間分布を再現することで、モニタリングの補完として活用可能である。, We developed an atmospheric dispersion calculation method that can respond to various needs for dispersion prediction in nuclear emergency and prepare database of information useful for planning of emergency response. In this method, it is possible to immediately get the prediction results for provided source term by creating a database of dispersion calculation results without specifying radionuclides, release rate and period except release point. By performing this calculation steadily along with meteorological data update, it is possible to immediately get calculation results for any source term and period from hindcast to short-term forecast. This function can be used for pre-accident planning such as optimization of monitoring plan and understanding events to be supposed for emergency response. Spatiotemporal distribution of radioactive materials reproduced by source term estimated inversely from monitoring based on this method is useful as a supplement to monitoring.

Published
2018

12. Selective Formation of Porous Pt Nanorods for Highly Electrochemically Efficient Neural Electrode Interfaces

Author

Ganji, Mehran, primary, Paulk, Angelique C., additional, Yang, Jimmy C., additional, Vahidi, Nasim W., additional, Lee, Sang Heon, additional, Liu, Ren, additional, Hossain, Lorraine, additional, Arneodo, Ezequiel M., additional, Thunemann, Martin, additional, Shigyo, Michiko, additional, Tanaka, Atsunori, additional, Ryu, Sang Baek, additional, Lee, Seung Woo, additional, Tchoe, Youngbin, additional, Marsala, Martin, additional, Devor, Anna, additional, Cleary, Daniel R., additional, Martin, Joel R., additional, Oh, Hongseok, additional, Gilja, Vikash, additional, Gentner, Timothy Q., additional, Fried, Shelley I., additional, Halgren, Eric, additional, Cash, Sydney S., additional, and Dayeh, Shadi A., additional

Published
2019
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13. 過去解析から短期予報まで任意の期間及び放出源情報に対する大気拡散計算結果を即座に提供可能な大気拡散データベース計算手法の開発(共同研究)

Author

寺田 宏明, Terada, Hiroaki, 都築 克紀, Tsuzuki, Katsunori, 門脇 正尚, Kadowaki, Masanao, 永井 晴康, Nagai, Haruyasu, 田中 孝典, Tanaka, Atsunori, 寺田 宏明, Terada, Hiroaki, 都築 克紀, Tsuzuki, Katsunori, 門脇 正尚, Kadowaki, Masanao, 永井 晴康, Nagai, Haruyasu, 田中 孝典, and Tanaka, Atsunori

Abstract

原子力緊急時の様々な大気拡散予測のニーズに対応するとともに、事前の環境モニタリング等の事故対応計画の策定に有効な情報をデータベースとして整備することが可能な大気拡散計算手法の開発を行った。本手法では、放出源情報のうち放出点以外の放射性核種、放出率、及び放出期間を特定することなく拡散計算を実施してデータベース化しておき、放出源情報を与えた際にその条件に基づく予測結果を即座に得ることが可能である。この計算を気象解析・予報データの更新に合わせて定常的に実行し、過去から数日先までの連続的なデータベースを整備することで、過去解析から短期の将来予測まで任意の期間及び放出源情報に対する計算結果を即座に作成可能である。この機能は、過去の様々な気象条件に対する拡散解析結果の分析により、モニタリング計画の最適化等の事前計画の立案に利用できる。また、様々な仮想放出源情報を用いた拡散解析により、緊急時対策を検討する上で想定すべき事象の把握が可能である。さらに、本手法に基づきモニタリング結果から放出源情報を逆推定して放射性物質の時空間分布を再現することで、モニタリングの補完として活用可能である。, We developed an atmospheric dispersion calculation method that can respond to various needs for dispersion prediction in nuclear emergency and prepare database of information useful for planning of emergency response. In this method, it is possible to immediately get the prediction results for provided source term by creating a database of dispersion calculation results without specifying radionuclides, release rate and period except release point. By performing this calculation steadily along with meteorological data update, it is possible to immediately get calculation results for any source term and period from hindcast to short-term forecast. This function can be used for pre-accident planning such as optimization of monitoring plan and understanding events to be supposed for emergency response. Spatiotemporal distribution of radioactive materials reproduced by source term estimated inversely from monitoring based on this method is useful as a supplement to monitoring., 著者所属: 日本原子力研究開発機構(JAEA), JAEA-Data/Code 2017-013

Published
2018

20. Development and Translation of PEDOT:PSS Microelectrodes for Intraoperative Monitoring

Author

Ganji, Mehran, primary, Kaestner, Erik, additional, Hermiz, John, additional, Rogers, Nick, additional, Tanaka, Atsunori, additional, Cleary, Daniel, additional, Lee, Sang Heon, additional, Snider, Jospeh, additional, Halgren, Mila, additional, Cosgrove, Garth Rees, additional, Carter, Bob S., additional, Barba, David, additional, Uguz, Ilke, additional, Malliaras, George G., additional, Cash, Sydney S., additional, Gilja, Vikash, additional, Halgren, Eric, additional, and Dayeh, Shadi A., additional

Published
2017
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21. Selective Formation of Porous Pt Nanorods for Highly Electrochemically Efficient Neural Electrode Interfaces

Author

Ganji, Mehran, Paulk, Angelique C., Yang, Jimmy C., Vahidi, Nasim W., Lee, Sang Heon, Liu, Ren, Hossain, Lorraine, Arneodo, Ezequiel M., Thunemann, Martin, Shigyo, Michiko, Tanaka, Atsunori, Ryu, Sang Baek, Lee, Seung Woo, Tchoe, Youngbin, Marsala, Martin, Devor, Anna, Cleary, Daniel R., Martin, Joel R., Oh, Hongseok, Gilja, Vikash, Gentner, Timothy Q., Fried, Shelley I., Halgren, Eric, Cash, Sydney S., and Dayeh, Shadi A.

Abstract

The enhanced electrochemical activity of nanostructured materials is readily exploited in energy devices, but their utility in scalable and human-compatible implantable neural interfaces can significantly advance the performance of clinical and research electrodes. We utilize low-temperature selective dealloying to develop scalable and biocompatible one-dimensional platinum nanorod (PtNR) arrays that exhibit superb electrochemical properties at various length scales, stability, and biocompatibility for high performance neurotechnologies. PtNR arrays record brain activity with cellular resolution from the cortical surfaces in birds and nonhuman primates. Significantly, strong modulation of surface recorded single unit activity by auditory stimuli is demonstrated in European Starling birds as well as the modulation of local field potentials in the visual cortex by light stimuli in a nonhuman primate and responses to electrical stimulation in mice. PtNRs record behaviorally and physiologically relevant neuronal dynamics from the surface of the brain with high spatiotemporal resolution, which paves the way for less invasive brain–machine interfaces.

Published
2024
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22. Autoclave Sterilization of PEDOT:PSS Electrophysiology Devices

Author

Uguz, Ilke, primary, Ganji, Mehran, additional, Hama, Adel, additional, Tanaka, Atsunori, additional, Inal, Sahika, additional, Youssef, Ahmed, additional, Owens, Roisin M., additional, Quilichini, Pascale P., additional, Ghestem, Antoine, additional, Bernard, Christophe, additional, Dayeh, Shadi A., additional, and Malliaras, George G., additional

Published
2016
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24. Development and Translation of PEDOT:PSS Microelectrodes for Intraoperative Monitoring.

Author

Ganji, Mehran, Kaestner, Erik, Hermiz, John, Rogers, Nick, Tanaka, Atsunori, Cleary, Daniel, Lee, Sang Heon, Snider, Jospeh, Halgren, Milan, Cosgrove, Garth Rees, Carter, Bob S., Barba, David, Uguz, Ilke, Malliaras, George G., Cash, Sydney S., Gilja, Vikash, Halgren, Eric, and Dayeh, Shadi A.

Subjects
NEURAL circuitry, MICROELECTRODES, OPTICAL microscopes, ELECTROPHYSIOLOGY, OXYGEN plasmas
Abstract

Abstract: Recording neural activity during neurosurgical interventions is an invaluable tool for both improving patient outcomes and advancing our understanding of neural mechanisms and organization. However, increasing clinical electrodes' signal‐to‐noise and spatial specificity requires overcoming substantial physical barriers due to the compromised metal electrochemical interface properties. The electrochemical properties of poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) based interfaces surpass those of current clinical electrocorticography electrodes. Here, robust fabrication process of PEDOT:PSS microelectrode arrays is demonstrated for safe and high fidelity intraoperative monitoring of human brain. PEDOT:PSS microelectrodes measure significant differential neural modulation under various clinically relevant conditions. This study reports the first evoked (stimulus‐locked) cognitive activity with changes in amplitude across pial surface distances as small as 400 µm, potentially enabling basic neurophysiology studies at the scale of neural micro‐circuitry. [ABSTRACT FROM AUTHOR]

Published
2018
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26. High Density Individually Addressable Nanowire Arrays Record Intracellular Activity from Primary Rodent and Human Stem Cell Derived Neurons.

Author

Ren Liu, Renjie Chen, Elthakeb, Ahmed T., Sang Heon Lee, Hinckley, Sandy, Khraiche, Massoud L., Scott, John, Deborah Pre, Yoontae Hwang, Tanaka, Atsunori, Ro, Yun Goo, Matsushita, Albert K., Xing Dai, Soci, Cesare, Biesmans, Steven, James, Anthony, Nogan, John, Jungjohann, Katherine L., Pete, Douglas V., and Webb, Denise B.

Published
2017
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27. (Invited) Strain Engineered Crack-Free GaN on Si for Integrated Vertical High Power GaN Devices with Si CMOS

Author

Dayeh, Shadi, Tanaka, Atsunori, Choi, Woojin, and Chen, Renjie

Abstract

The ability to grow thin GaN layers on Si substrates has led to the development of lateral high power and high-speed devices such as GaN HEMTs. These devices have already demonstrated promising performance and have been adopted for mass market. But lateral devices require large drain/gate separation to sustain high voltage impairing cost effectiveness. This highlights the need for growth of thick GaN layers to enable vertical high power device architectures and to achieve high performance and attain high breakdown voltages in small chip area. This paper presents a successful growth of over 10um thick crack-free GaN on Si by engineering the strain induced by thermal mismatch between GaN and Si. We discuss the origin of cracking and introduce a surface strain-relief mechanism in 0.5mm diameter GaN dots to overcome thermal mismatches. The first demonstration of vertical thick GaN Schottky diodes on Si will be presented. To fully exploit these results of GaN power devices on Si, side-by-side integration of GaN and CMOS circuitry elements is necessary. We have assessed and validated the compatibility of the GaN-CMOS process. These advances can pave the way for commercialization of next generation compact and efficient power systems that are composed of monolithically integrated GaN and Si technologies.

Published
2016

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