Language：Others   Publishing type：Research paper (scientific journal)  

Dielectrophoretic (DEP) manipulation of a diamond particle has potential application in the detection of DNA or other bio-molecules. We investigate the fundamental DEP and surface properties of submicron diamond particles. Diamond particles were dispersed in a NaCl solution and dropped on a castle-walled electrode. An AC electric field was applied to determine the DEP crossover frequency as a function of the solution conductivity. The surface conductance of the diamond particles was then evaluated from the parametrical fitting of the crossover frequencies. The diamond surface layer was shown to exhibit a rather high conductance, although bulk diamond is insulative.

DOI： 10.35848/1347-4065/ab7baf

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.35848/1347-4065/ab7baf

Language：English   Publishing type：Research paper (scientific journal)  

For sp² or sp³ carbon material growth, it is important to investigate the precursors or intermediates just before growth. In this study, the density of ethylene (C₂H₄) outside the plasma discharge space and just before reaching the carbon nanotube (CNT) growth region is investigated by vacuum ultraviolet absorption spectroscopy for plasma discharge in an antenna-type remote plasma chemical vapor deposition with a CH₄/H₂ system, with which the growth of very long (≈0.5 cm) CNT forests is achieved. Single-wall CNT forests have the potential for application as electrodes in battery cells, vertical wiring for high current applications, and thermal interface materials. It is observed that the plasma discharge decomposes the CH₄ source gas and forms C₂H_x species, which reversibly reform to C₂H₄ in the plasma-off state. In addition, the density of the formed C₂H₄ has a strong correlation to the CNT growth rate. Therefore, the C₂H₄ density is a good indicator of the density of C₂H_x species for CNT growth in the CH₄/H₂ plasma system.

DOI： 10.1002/smll.201901504

Language：English   Publishing type：Research paper (scientific journal)  

Hydrogen-terminated diamond metal-insulator-semiconductor field-effect transistors are candidates for power devices that require a high breakdown field and stable, high-frequency operation. A two-dimensional hole-gas layer can form on H-terminated diamond surfaces. To understand the electrical properties of bare H-terminated diamond surfaces, we investigate the surface impurities on a H-terminated diamond surface in a vacuum-gap gate structure, which uses a H-terminated diamond channel and a vacuum gap as gate dielectrics. To obtain a bare surface without surface adsorbate, the device is annealed in a vacuum. The transconductance is increased by removing adsorbates. The mobility and interface-state density at the H-terminated diamond surface with no adsorbates are 25 cm^2 V^-1 s^-1 and 1 × 10^12 cm^-2 eV^-1, respectively.

DOI： 10.1063/1.5099395

Language：English   Publishing type：Research paper (scientific journal)  

Power semiconductor devices require low on-resistivity and high breakdown voltages simultaneously. Vertical-type metal-oxide-semiconductor field-effect transistors (MOSFETs) meet these requirements, but have been incompleteness in diamond. Here we show vertical-type p-channel diamond MOSFETs with trench structures and drain current densities equivalent to those of n-channel wide bandgap devices for complementary inverters. We use two-dimensional hole gases induced by atomic layer deposited Al2O3 for the channel and drift layers, irrespective of their crystal orientations. The source and gate are on the planar surface, the drift layer is mainly on the sidewall and the drain is the p+ substrate. The maximum drain current density exceeds 200 mA mm^-1 at a 12 μm source-drain distance. On/off ratios of over eight orders of magnitude are demonstrated and the drain current reaches the lower measurement limit in the off-state at room temperature using a nitrogen-doped n-type blocking layer formed using ion implantation and epitaxial growth.

DOI： 10.1038/s41598-018-28837-5

Language：English   Publishing type：Research paper (scientific journal)  

Understanding the electrical contact properties of carbon nanotube (CNT) ends is important to use the high conductance of CNTs in the CNT on-axis direction in applications such as through-silicon via structures. In this study, we experimentally evaluated the contact resistivity between single-/multi-walled CNT ends and a metal nanoprobe using conductive atomic force microscopy (C-AFM). To validate the measured end contact resistivity, we compared our experimentally determined value with that obtained from numerical calculations and reported values for side contact resistivity. The contact resistivity normalized by the length of the CNT ends was 0.6-2.4 × 10^6 Ω nm for single-walled CNTs. This range is 1-2 orders of magnitude higher than that determined theoretically. The contact resistivity of a single-walled CNT end with metal normalized by the contact area was 2-3 orders of magnitude lower than that reported for the resistivity of a CNT sidewall/metal contact. For multi-walled CNTs, the measured contact resistivity was one order of magnitude higher than that of a CNT forest grown by remote plasma-enhanced chemical vapor deposition, whereas the contact resistivity of a top metal electrode was similar to that obtained for a single-walled CNT forest.

DOI： 10.1063/1.5027849

Language：English   Publishing type：Research paper (scientific journal)  

The hydrogen-terminated diamond surface (C-H diamond) has a two-dimensional hole gas (2DHG) layer independent of the crystal orientation. A 2DHG layer is ubiquitously formed on the C-H diamond surface covered by atomic-layer-deposited-Al2O3. Using Al2O3 as a gate oxide, C-H diamond metal oxide semiconductor field-effect transistors (MOSFETs) operate in a trench gate structure where the diamond side-wall acts as a channel. MOSFETs with a side-wall channel exhibit equivalent performance to the lateral C-H diamond MOSFET without a side-wall channel. Here, a vertical-type MOSFET with a drain on the bottom is demonstrated in diamond with channel current modulation by the gate and pinch off.

DOI： 10.1063/1.4958889

Language：English   Publishing type：Research paper (scientific journal)  

Understanding of the contact conductivity of carbon nanotubes (CNTs) will contribute to the further application of CNTs for electronic devices, such as thin film transistors whose channel or electrode is made of dispersed CNTs. In this study, we estimated the contact conductivity of a CNT/CNT interface from the in-plane conductivity of an uncapped CNT forest on SiC. Investigation of the electrical properties of dense CNT forests is also important to enable their electrical application. The in-plane conductivity of a dense CNT forest on silicon carbide normalized by its thickness was measured to be 50 S/cm, which is two to three orders of magnitude lower than the conductivity of a CNT yarn. It was also found that both the CNT cap region and the CNT bulk region exhibit in-plane conductivity. The contact conductivity of CNTs was estimated from the in-plane conductivity in the bulk region. Dense and uncapped CNT forest can be approximated by a conductive mesh, in which each conductive branch corresponds to the CNT/CNT contact conductance. The evaluated contact conductivity was in good agreement with that calculated from the tunneling effect.

DOI： 10.1021/acs.jpcc.5b11815

Language：English   Publishing type：Research paper (scientific journal)  

Electrical contacts to silicon carbide with low contact resistivity and high current durability are crucial for future SiC power devices, especially miniaturized vertical-type devices. A carbon nanotube (CNT) forest formed by silicon carbide (SiC) decomposition is a densely packed forest, and is ideal for use as a heat-dissipative ohmic contact in SiC power transistors. The contact resistivity and Schottky barrier height in a Ti/CNT/SiC system with various SiC dopant concentrations were evaluated in this study. Contact resistivity was evaluated in relation to contact area. The Schottky barrier height was calculated from the contact resistivity. As a result, the Ti/CNT/SiC contact resistivity at a dopant concentration of 3 × 10^18 cm-3 was estimated to be ∼1.3 × 10^-4 Ω cm2 and the Schottky barrier height of the CNT/SiC contact was in the range of 0.40-0.45 eV. The resistivity is relatively low for SiC contacts, showing that CNTs have the potential to be a good ohmic contact material for SiC power electronic devices.

DOI： 10.1063/1.4916248

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1080/26941112.2024.2423643

Web of Science

researchmap

Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

<p>1．はじめに</p><p>静電界による細胞操作として，誘電泳動について紹介する。“誘電泳動”は英語で“dielectrophoresis（DEP）”と書く。電気泳動“electrophoresis”に誘電体“dielectric”の“di-”を付け加えた語であり，液体媒体中，とりわけ誘電率が大きな水中に存在する誘電体微粒子や細胞などに</p>

DOI： 10.1541/ieejjournal.144.631

Scopus

CiNii Research

Publishing type：Research paper (scientific journal)   Publisher：IEEE Sensors Letters  

Nonthermal atmospheric-pressure discharge plasma is considered important for sterilization. Reactive species, such as active oxygen species, radicals, and nitrate ions, generated by the discharge plasma damage the target bacterial cell wall/membrane and DNA. Several plasma sterilization methods have been proposed, including dielectric barrier discharge (DBD). To achieve effective sterilization, it is necessary to evaluate their characteristics using many parameters. This letter aims to demonstrate a proof-of-concept of a novel biological indicator for plasma sterilization. A biological indicator is used to verify sterilization outcomes. We employ DNA-labeled microbeads as biological indicators for the rapid visualization of plasma sterilization. This is based on our recently developed method for visual detection of DNA molecules. If plasma-derived factors cause the degradation of the DNA attached to the microbeads, this can be confirmed by visualization. Herein, we present the correlation between sterilization and visualization in the case of DBD. This method offers a rapid evaluation of plasma sterilization because it easily and quickly determines the sterilization capability of the plasma.

DOI： 10.1109/LSENS.2024.3420437

Web of Science

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Biosensors and Bioelectronics: X  

Nucleic acid amplification tests (NATs), such as genetic tests using polymerase chain reaction (PCR), are sensitive methods for detecting pathogens and food contamination. The rapid, easy, and inexpensive detection of amplicons, DNA, or RNA is key to realizing on-site NATs. We have previously developed a novel amplicon detection method using magnetic microbeads based on the hydrophobicity of DNA in deionized water. In this study, we aimed to expand the method for the detection of multiplex DNA amplicons. Tagged primers and probes for selective attachment were used to detect amplicons from two strawberry pathogens. The amplicon-labeled magnetic microbeads were placed in the round-bottom well of a hydrophilic glass substrate. The attachment of amplicons to the magnetic microbeads changed their surface from hydrophilic to hydrophobic. The magnetized microbeads concentrated at the bottom when the substrate was placed on a permanent magnet, and the concentrated microbeads were easily recognizable by the naked eye. Microbeads without amplicons were adsorbed over a broad area of the bottom of the glass well owing to their hydrophilicity. The appropriate tag probe was attached to specific amplicons for detection, and each amplicon from multiplex PCR was selectively detected within approximately 15 min. Notably, this method requires no electric power and contributes to the realization of on-site NAT detection. This study presents a simple and rapid method for the selective detection of multiplex PCR amplicons using DNA–DNA hybridization.

DOI： 10.1016/j.biosx.2024.100461

Scopus

researchmap

Language：Others   Publishing type：Research paper (scientific journal)   Publisher：Japanese Journal of Applied Physics  

<jats:title>Abstract</jats:title>
<jats:p>Liquid biopsies for cancer diagnosis using exosomes have been studied. Separating cancer cell-derived exosomes from a sample mixture is crucial, especially when they do not dominate the sample at an early stage of cancer. A method based on their electrical properties could provide a simpler separation than immune-affinity methods. We have identified the differences in electrical properties of cancerous exosomes from those of normal ones, suggesting the possibility for their dielectrophoresis (DEP) based separation. This study separated cancerous exosomes from a mixture of normal exosomes. The DEP of fluorescence-labeled exosomes suspended in aqueous media with varying electrical conductivities was investigated. The observed DEP was quantitatively evaluated using the normalization method accounting for the fluorescence fading effect. The results showed that the cancerous exosomes were preferentially concentrated under the appropriate conditions. This suggests that DEP can enable the selective capture of cancer exosomes without chemical labeling.</jats:p>

DOI： 10.35848/1347-4065/ad2657

Web of Science

Scopus

researchmap

Publisher：International Journal of Nanotechnology  

Metal-organic chemical vapour deposition (MOCVD) was used to grow AlGaN/GaN high electron mobility transistor (HEMT) on a sapphire substrate with different thicknesses of the GaN cap layer from 1.5 nm to 2.5 nm for open-gate chromium (Cr) AlGaN/GaN HEMT structures. High-resolution X-ray diffraction (HRXRD) was utilised to investigate the structural characteristics of the materials. A non-annealing technique was used to reduce the negatively impacted on the electrical properties is bad for the function of the device. The use of the GaN cap layer improved the performance of the devices as the resistance decreased with increasing the thickness of the GaN cap layer. Here we demonstrate the comparison between different thicknesses of GaN cap layers to improve the resistivity of the device.

DOI： 10.1504/IJNT.2024.141755

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

Dielectrophoretic impedance measurement (DEPIM) is a method using a microelectrode for measuring a target suspended in a solution by combining dielectrophoretic (DEP) trapping of the target and simultaneous measurement of impedance varied with the trapping. DEPIM can be utilized to detect bacteria and viruses without any chemical additive since DEPIM efficiency depends on the DEP trapping dominated by the microelectrode shape. This letter aims to demonstrate a new microelectrode design to increase bacteria detection efficiency instead of the conventional interdigitated microelectrode. The microelectrode having a serpentine gap as a sinusoidal waveform profile was proposed. The new microelectrode was compared with the interdigitated one in numerical simulation and experiments. The numerical simulation demonstrates that the serpentine microelectrode traps all the targets in a laminar flow in a microchannel. In contrast, the interdigitated one placed parallel to the microchannel does not because the target flowing away from the edges of the microelectrode cannot be trapped. The experiments using three kinds of bacteria were carried out. It was demonstrated that the serpentine microelectrode represented a sensitivity 104 times higher than the interdigitated one when a small amount of the sample solution was tested for a short time (1 min).

DOI： 10.1109/lsens.2023.3297315

Web of Science

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Trans Tech Publications, Ltd.  

Metal organic chemical vapor deposition (MOCVD) was used to grow AlGaN/GaN HEMT on a sapphire substrate with a 3.0 nm GaN cap and a sample without a GaN cap. High resolution X-ray diffraction (HRXRD) was utilized to investigate the structural characteristics of the materials. The relationship between the electrical properties and two-dimensional electron gas (2DEG) I-V and Hall Effect measurement. The I-V measurement was used to investigate the resistance properties of AlGaN/GaN heterostructures. Hall Effect measurement was used to quantify electron mobility and sheet carrier concentration in both samples. The sample with a 3.0 nm GaN cap exhibited excellent electrical properties with 436.8 Ω/sq sheet resistivity and possessed a high value of sheet carrier concentration 3.46E+14 per cm².

DOI： 10.4028/p-9qdk55

Scopus

researchmap

Publisher：Proceedings of IEEE Sensors  

Exosomes derived from cells have great potential as a biomarker for early-stage cancer diagnosis. Recently, we demonstrated the separation of exosomes derived from cancer and normal cells, respectively, utilizing dielectrophoresis (DEP). In the separation, the exosomes were labeled with fluorescent dyes to observe by an optical microscope. In this report, an evaluation method of the exosome concentration based on the fluorescence intensity was proposed. The evaluation method includes the effect of the photobleaching of fluorescent dye to improve the accuracy. The photobleaching property was experimentally investigated in order to obtain a calibration equation. The proposed method was applied to the quantitative evaluation of DEP-captured exosomes.

DOI： 10.1109/SENSORS56945.2023.10325029

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1063/5.0124891

Language：Others   Publishing type：Research paper (scientific journal)  

Carbon nanotubes (CNTs) are promising materials for gas sensing because of their large specific area and high sensitivity to charge differentiation. In CNT-based field-effect transistors (FETs) for gas sensing, both CNT potential modulation in the channels and Schottky barrier height modulation at the CNT/metal electrode contact influence the current properties. However, researchers have not used Schottky barrier height modulation for gas detection. To investigate and compare the effects of Schottky barrier height modulation and CNT channel potential modulation on NO₂ gas exposure, we fabricated ambipolar CNT FETs by the dielectrophoretic assembly. We exposed CNT FET gas sensors to N₂ gas containing 100-ppb NO₂ and observed two different responses in the electric properties: a steady current shift in the positive direction in the hole-conduction region because of the channel potential modulation, and an abrupt decrease in transconductance in the electron-conduction region because of the Schottky barrier modulation. The CNT channels and CNT/metal contact both contributed to the sensor response, and the modulation rate of the Schottky barrier was higher than that of the CNT potential shift in the channel.

DOI： 10.1063/5.0124891

Language：English   Publisher：John Wiley & Sons Australia, Ltd  

ニワトリc-Kitタンパク質の716番から728番のアミノ酸残基からなる部分ペプチドに対するポリクローナル抗体をウサギで作製し、その特異性をウェスタンブロッティング解析と免疫細胞化学染色の両方で検証した。抗ニワトリc-Kit抗体と抗α平滑筋アクチン(αSMA)抗体との共染色により、ニワトリ後腸の輪状筋層と縦走筋層に存在するカハール介在細胞(ICC)を可視化することに成功した。分化初期段階のICCと平滑筋細胞の共通前駆細胞はαSMAとc-Kitの両方が陽性であり、後期段階では分化したICCと平滑筋細胞はそれぞれc-KitとαSMAのみを発現していた。粘膜下層から輪状筋層まで放射状に伸びる新規のICC集団も発見した。さらに、抗ニワトリc-Kit抗体は、透明化した後腸における個々のICCを描出した。以上より、本研究で作製した抗ニワトリc-Kit抗体は、ニワトリ胚の蠕動運動の研究を促進することが期待された。

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Inderscience Publishers  

The behaviour and performance of p-doped GaN and undoped GaN thin film in the presence of methanol gas were studied. GaN thin films were grown using metal organic chemical vapour deposition (MOCVD), which were then fabricated into resistive sensors. Gas-sensing characterisation with the in-house gas chamber demonstrates that the resistive sensors based on undoped and p-doped GaN exhibit high sensitivity and fast response to methanol vapour in less than a minute, as well as excellent stability in room temperature operations. Without high temperature measurements, both undoped and p-doped GaN resistive sensors exhibit significant resistance variation and response over time when exposed to methanol, albeit with distinct properties. Here we demonstrate the comparison between the two and their sensing capabilities of both p-doped GaN and undoped GaN thin film resistive sensors.

DOI： 10.1504/ijnt.2022.124520

Web of Science

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3390/s22093279

Language：English   Publishing type：Research paper (scientific journal)  

Dielectrophoresis (DEP) refers to a type of electrical motion of dielectric particles. Because DEP is caused by particle polarization, it has been utilized to characterize particles. This study investigated the DEP of three types of exosomes, namely bovine milk, human breast milk, and human breast cancer exosomes. Exosomes are kinds of extracellular vesicles. The crossover frequencies of the exosomes were determined by direct observation of their DEPs. Consequently, bovine and human milk exosomes showed similar DEP properties, whereas the cancer exosomes were significantly different from the others. The membrane capacitance and conductivity of the exosomes were estimated using determined values. A significant difference was observed between bovine and human milk exosomes on their membrane capacitance. It was revealed that the membrane capacitances of human breast milk and human breast cancer exosomes were almost identical to those of their host cells and the conductivity of the exosomes were much lower than that of the host cell. Based on these results, DEP separation of the human breast milk and cancer exosomes was demonstrated. These results imply that DEP can be utilized to separate and identify cancer exosomes rapidly. Additionally, our method can be utilized to estimate the electric property of other types of extracellular vesicles.

DOI： 10.3390/s22093279

Publisher：MicroTAS 2022 - 26th International Conference on Miniaturized Systems for Chemistry and Life Sciences  

DNase I has been considered a biomarker for early diagnosing myocardial infarction. This study demonstrated a novel DNase I detection utilizing DNA-labeled microbeads. The DNA on the dielectric microbeads was cleaved by DNase I. Then, the microbeads were applied to dielectrophoresis (DEP)-based impedance measurement. Because the microbead's DEP depends on the amount of the attached DNA, the DNase I cleavage decreases the DEP force to trap them on a microelectrode, resulting in the decrease of the conductance change. As a result, the method detected 10-6 U of DNase I in a 40 µl reaction solution within 30 min.

Scopus

Language：Japanese  

Detection of CO converted from CF₄ in SF₆ by high frequency surface discharge

DOI： 10.11527/jceeek.2021.0_270

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.34343/ijpest.2021.15.e02010

Language：English   Publishing type：Research paper (scientific journal)  

In this paper, a new diagnosis method for SF6 gas-insulated switchgear (GIS) is proposed based on decomposition gas analysis. We focus on residual CF4 gas in GIS, which is a decomposition gas generated in GIS via partial or arc discharge. Unlike other decomposition gases, which can be removed by the gas absorbent, CF4 accumulates during in-service operation, enabling trend-based GIS condition monitoring. Because direct CF4 detection using commercially available gas sensors is difficult, we propose a novel indirect detection method in which CF4 is converted into CO and CO2 by a dielectric barrier discharge (DBD). A DBD-treated artificial gas mixture composed of CF4, O2, and SF6 was analyzed via Fourier transform infrared spectroscopy (FTIR). It was found that CO and CO2 are simultaneously generated when the CF4 gas concentration is higher than 100 ppm, which is close to the target CF4 concentration for GIS diagnosis. To demonstrate rapid, simple, and on-site diagnostic capabilities, a commercial electrochemical CO gas sensor was employed to detect DBD-converted CO gas. The CO concentration quantified by the calibrated gas sensor was almost identical to that obtained via FTIR. As the CF4-to-CO conversion rate is expected to improve with an optimum DBD reactor design, the proposed scheme could be applicable to GIS diagnosis.

DOI： 10.34343/ijpest.2021.15.e02010

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1541/ieejsmas.141.233

Language：Japanese   Publishing type：Research paper (scientific journal)  

Nucleic amplification tests (NATs) are sensitive and specific methods to diagnose infectious diseases. Real-time polymerase chain reaction (PCR) is the gold standard, but it requires expensive apparatus and regents because of fluorescent detection. This study performed a combination of a conventional PCR and microbeads dielectrophoresis (DEP)-based DNA detection method to detect the SARS-CoV-2 gene quantitatively. SARS-CoV-2 is a virus causing COVID-19 and has caused the pandemic worldwide. In the microbeads DEP-based DNA detection method, the amplified DNA, amplicon, is attached to microbeads, the amplicon-labeled microbeads are detected by dielectrophoretic impedance measurement. As a result, the technique demonstrated that same sensitivity as that of real-time PCR. Our method enables the cheap diagnosis of infectious disease instead of expensive real-time PCR.

DOI： 10.1541/ieejsmas.141.233

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/d0an02349c

Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/CMD48350.2020.9287294

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/ted.2020.3019020

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/cmd48350.2020.9287294

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TED.2020.3019020

Language：Japanese  

Detection of CO converted from CF₄ in SF₆ by dielectric barrier discharge

DOI： 10.11527/jceeek.2020.0_292

Language：English   Publishing type：Research paper (scientific journal)  

Gas sensors with carbon nanotubes (CNTs) and tin dioxide (SnO2) nanoparticles for nitrogen dioxide (NO2) detection are fabricated using a two-step dielectrophoretic (DEP) assembly method, and the NO2 gas detection properties are investigated. For the fabrication of the sensor, CNTs assemble between electrodes by a DEP force, followed by SnO2 nanoparticle decoration also by a DEP assembly method, and the assembled CNTs act as high electric field electrodes. The formed CNT/SnO2 gas sensors exhibit a sharp increase in resistance followed by a gradual decrease upon NO2 exposure. pn hetero-junctions are formed between the CNTs and the SnO2 nanoparticles, and the resistance shift of the depletion region in the CNTs at the pn hetero-junction induces the sharp increase in the resistance.

DOI： 10.1063/5.0008188

Language：English   Publishing type：Research paper (scientific journal)  

We present a miniaturized vertical-type two-dimensional hole gas (2DHG) diamond metal-oxide-semiconductor field-effect transistor (MOSFET) by adopting a gate-source overlapping structure. We developed a 2μm-wide trench and disposed a part of the gate electrode to overlap the Al₂O₃ insulator film on the source electrode to eliminate the space between source and gate electrode. We obtained the maximum drain current density of I_D =12800 A/cm² at V_DS =-50 V and the specific on-resistance of R_ON =3.2 m}Ω cm² at V_DS =-10 V and confirmed their improvement by the miniaturization of devices and reduction of source to gate resistance. In addition, the drain current on/off ratio was 7 orders magnitude even at 200 °C with the formation of a highly concentrated, thick nitrogen-doped layer as the current blocking layer.

DOI： 10.1109/LED.2019.2953693

Language：English   Publishing type：Research paper (scientific journal)  

We present a miniaturized vertical-type two-dimensional hole gas (2DHG) diamond metal-oxide-semiconductor field-effect transistor (MOSFET) by adopting a gate-source overlapping structure. We developed a 2-mu m-wide trench and disposed a part of the gate electrode to overlap the Al2O3 insulator film on the source electrode to eliminate the space between source and gate electrode. We obtained the maximum drain current density of I-D = 12800 A/cm(2) at V-DS = -50 V and the specific on-resistance of R-ON = 3.2 mcm(2) at V-DS = -10 V and confirmed their improvement by the miniaturization of devices and reduction of source to gate resistance. In addition, the drain current on/off ratio was 7 orders magnitude even at 200 degrees C with the formation of a highly concentrated, thick nitrogen-doped layer as the current blocking layer.

DOI： 10.1109/led.2019.2953693

Language：Others   Publishing type：Research paper (scientific journal)  

© 2020 Author(s). Electrokinetic motion of dielectric microparticles is used in various applications, as the dielectrophoresis (DEP) of the microparticles depends on their polarization in an electric field. This polarization, given by the Clausius-Mossotti (CM) factor, depends on a particle's surface conductance. This study demonstrates that DNA can induce changes to the nature of the traveling-wave DEP (twDEP) force on a microparticle. As DNA molecules have electric charges on their phosphate backbones, attaching these molecules to the surface of a microparticle increases its surface conductance, resulting in a change in the imaginary part of the CM factor. We conducted image-based analysis of the twDEP velocity of ensembles of microparticles labeled with DNA in the range of 100-10 000 molecules per microparticle. Our experiments revealed that, in addition to being proportional to the number of DNA molecules on a particle, the twDEP velocity of sparsely labeled microparticles (∼100 DNA molecules per microparticle) can be distinguished from that of a bare one, suggesting that the twDEP velocity measurement can be utilized as a DNA detection method.

DOI： 10.1063/1.5129725

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1063/1.5129725

Language：English   Publishing type：Research paper (scientific journal)  

We propose a new microfluidic device that can be used to determine the change in the negative dielectrophoresis (n-DEP) of dielectric microbeads when a small amount of DNA is attached to them. We previously proposed a DNA detection method based on changes in the DEP of microbeads induced by the attachment of DNA. When target DNA is attached to the microbeads having n-DEP property, the DEP changes from negative to positive. This occurs because electric charges of the DNA increase the surface conductance of the microbeads. Thus, only the DNA-labeled microbeads are attracted to a microelectrode by positive DEP. The trapped DNA-labeled microbeads can be counted by dielectrophoretic impedance measurements. A large amount of DNA (approximately 10⁵ DNA molecules) is required to change the DEP from negative to positive. Even though this method can be combined with DNA amplification, reducing the amount of DNA required can help us to shorten the reaction time. In this study, we aimed to detect DNA less than 10⁵ DNA molecules by determining the change in the n-DEP change. To achieve this, we proposed a simple microfluidic device consisting of a single microchannel and a single pair of microelectrodes. Numerical simulations revealed that the device can identify the slight change in the n-DEP of the microbeads corresponding to the attachment of a small amount of DNA. In practical experiments, the fabricated device distinguished 10-1000 DNA molecules per microbead. This method represents a fast and easy method of DNA detection when combined with DNA amplification techniques.

DOI： 10.1063/1.5124419

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.1063/1.5124419

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/pssa.201900227

Language：Japanese  

Reproducibility of CF₄ detection characteristics of SnO₂ gas sensor fabricated by dielectrophoresis

DOI： 10.11527/jceeek.2019.0_325

Language：Others   Publishing type：Research paper (scientific journal)  

Correlation between the Carbon Nanotube Growth Rate and Byproducts in Antenna‐Type Remote Plasma Chemical Vapor Deposition Observed by Vacuum Ultraviolet Absorption Spectroscopy

DOI： 10.1002/smll.201901504

Language：English   Publishing type：Research paper (scientific journal)  

Normally-OFF Two-Dimensional Hole Gas Diamond MOSFETs Through Nitrogen-Ion Implantation
Diamond is a promising material for power applications owing to its excellent physical properties. Two-dimensional hole gas (2DHG) diamond metal-oxide-semiconductor field-effect transistors (MOSFETs) with hydrogen-terminated (C-H) channel have high current densities and high breakdown fields but often show normally-ON operation. From the viewpoint of safety, normally-OFF operation is required for power applications. In this letter, we used ion implantation to form a shallow and thin nitrogen-doped layer below the C-H channel region, which realized normally OFF operation. Nitrogen-ion implanted length is fixed at 5 or 10 mu m. Nitrogen is a deep donor (1.7 eV) and the nitrogen-doped layer prevents hole accumulation near the surface. The threshold voltage was as high as -2.5 V and no obvious dependence on the threshold voltage of nitrogenion implanted length is observed. The breakdown field was 2.7 MV/cm at room temperature. Of 64 devices with a common gate length, 75% showed normally-OFF operation. We confirmed the threshold voltage shift by a thin and shallow nitrogen-doped layer formed by ion implantation.

DOI： 10.1109/led.2019.2912211

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.1063/1.5099395

Language：English   Publishing type：Research paper (scientific journal)  

Selective growth techniques are believed to be the most effective approaches in the fabrication of diamond devices. Herein, the contamination from antenna and mask damage that causes poor performance in electronic applications is overcome with a high-quality diamond film on Ib (100) substrate, obtained by utilizing point-arc remote microwave plasma chemical vapor deposition (MPCVD). Scanning electron microscope (SEM) images and energy dispersive X-ray (EDX) mapping suggest that the diamond nucleation and selective growth occurred only in unmasked regions. Crystalline quality is evaluated by Raman spectra. Mo concentration from the antenna is detected with secondary ion mass spectroscopy (SIMS) at only a background level in the selectively grown diamond, indicating that the films are free of contaminant from the antenna, at three orders of magnitude lower than the impurity concentration in films selectively grown by typical hot filament CVD. Moreover, the moderate growth rate (approximately 50 nm h⁻¹) enables high reproducibility, which is of great importance for the precise control thickness of the selective growth layer, and thus the proposed method offers significant potential for the architecture modification of diamond devices.

DOI： 10.1002/pssa.201900227

Language：English   Publishing type：Research paper (scientific journal)  

Diamond is a promising material for power applications owing to its excellent physical properties. Two-dimensional hole gas (2DHG) diamond metal-oxide-semiconductor field-effect transistors (MOSFETs) with hydrogen-terminated (C-H) channel have high current densities and high breakdown fields but often show normally- ON operation. From the viewpoint of safety, normally- OFF operation is required for power applications. In this letter, we used ion implantation to form a shallow and thin nitrogen-doped layer below the C-H channel region, which realized normally- OFF operation. Nitrogen-ion implanted length is fixed at 5 or 10 \mu \text{m}. Nitrogen is a deep donor (1.7 eV) and the nitrogen-doped layer prevents hole accumulation near the surface. The threshold voltage was as high as -2.5 V and no obvious dependence on the threshold voltage of nitrogen-ion implanted length is observed. The breakdown field was 2.7 MV/cm at room temperature. Of 64 devices with a common gate length, 75% showed normally- OFF operation. We confirmed the threshold voltage shift by a thin and shallow nitrogen-doped layer formed by ion implantation.

DOI： 10.1109/LED.2019.2912211

Language：English   Publishing type：Research paper (scientific journal)  

Key factors in C 1s photoelectron spectroscopy for realistic samples of single crystal diamonds are remarked. Basic equations for angle-dependent photoelectron spectroscopy applied to single crystal diamond samples are described in Appendix A. Carbon 1s photoelectron spectroscopic works so far reported for hydrogen-terminated and oxygen-terminated diamond (001) and (111) samples were reviewed placing special attention on surface C 1s components with reference to the key factors. The results showed diversity in C 1s photoelectron spectra so far reported. We had three specific subjects of the study in C 1s XPS; the first is that we have reconfirmed the phenomenon that surface conductive layers resumed when smooth non-doped CVD C(111)-O samples were annealed in vacuum [Diam.Rela.Mate.18(2009)206]. A single C 1s XPS surface component was found for a smooth C(111)-O sample before the vacuum-anneal, which was attributed to surface carbon atoms in C–O–H bonding. The second subject is that dependence of C 1s XPS spectra on surface sensitivity has been measured for all the samples with different surface roughness of C(001)-O, C(111)-O, C(001)-H, and C(111)-H. The results were converted to the energy difference between the Fermi-level (Ef) and valence band maximum (Ev) on the probing depth from the surface. All the samples showed downward bending of Ev toward the surface. For the C(001)-H samples, this was a reconfirmation of previous work [Surf.Sci.604(2010)1148]. For the C(001)-H and C(111)-H samples, various degrees of downward band bending toward surface were observed and analyzed with two-dimensional band simulation. It was concluded that another source of holes such as shallow acceptors is present in a deeper region of the surface in addition to holes very close to surface caused by the charge-transfer-doping. The third subject is that C 1s XPS spectra for superconducting C(111)-O samples showed a lattice distortion of ~9 monolayers near the surface.

DOI： 10.1016/j.diamond.2019.01.017

Language：Others   Publishing type：Research paper (scientific journal)  

Carbon 1s X-ray photoelectron spectra of realistic samples of hydrogen-terminated and oxygen-terminated CVD diamond (111) and (001)
© 2019 Elsevier B.V. Key factors in C 1s photoelectron spectroscopy for realistic samples of single crystal diamonds are remarked. Basic equations for angle-dependent photoelectron spectroscopy applied to single crystal diamond samples are described in Appendix A. Carbon 1s photoelectron spectroscopic works so far reported for hydrogen-terminated and oxygen-terminated diamond (001) and (111) samples were reviewed placing special attention on surface C 1s components with reference to the key factors. The results showed diversity in C 1s photoelectron spectra so far reported. We had three specific subjects of the study in C 1s XPS; the first is that we have reconfirmed the phenomenon that surface conductive layers resumed when smooth non-doped CVD C(111)-O samples were annealed in vacuum [Diam.Rela.Mate.18(2009)206]. A single C 1s XPS surface component was found for a smooth C(111)-O sample before the vacuum-anneal, which was attributed to surface carbon atoms in C–O–H bonding. The second subject is that dependence of C 1s XPS spectra on surface sensitivity has been measured for all the samples with different surface roughness of C(001)-O, C(111)-O, C(001)-H, and C(111)-H. The results were converted to the energy difference between the Fermi-level (Ef) and valence band maximum (Ev) on the probing depth from the surface. All the samples showed downward bending of Ev toward the surface. For the C(001)-H samples, this was a reconfirmation of previous work [Surf.Sci.604(2010)1148]. For the C(001)-H and C(111)-H samples, various degrees of downward band bending toward surface were observed and analyzed with two-dimensional band simulation. It was concluded that another source of holes such as shallow acceptors is present in a deeper region of the surface in addition to holes very close to surface caused by the charge-transfer-doping. The third subject is that C 1s XPS spectra for superconducting C(111)-O samples showed a lattice distortion of ~9 monolayers near the surface.

DOI： 10.1016/j.diamond.2019.01.017

Language：English   Publishing type：Research paper (scientific journal)  

Thin films of single-walled carbon nanotubes (SWNTs) possess high potential for use in flexible electrochemical sensors in wearable medical devices. However, the electrochemical activity of such materials is not yet fully understood. We studied the enhancement in electrochemical activity of SWNT-based flexible electrochemical sensors. To exclude the effect of surface contaminations from the fabrication processes on the electrochemical activity, we introduced the dry process for high-quality and clean SWNT film formation and the clean device fabrication process with a protective layer. So-fabricated SWNT electrodes exhibited a low electron transfer rate. Electrochemical functionalization with an H₂SO₄ solution successfully enhanced the electrochemical activity of the SWNT electrode for the inner sphere probes such as [Fe(CN)₆]^4−/3−. This method is quite gentle and controllable, but also effective at increasing the electron transfer rate without either degrading the potential window. We found out that there was a correlation between the electron transfer rate and the amount of defects evaluated from Raman scattering spectroscopy. XPS analysis showed that the functionalization process introduced C–O and C[dbnd]O species, suggesting that these species constituted active sites for inner sphere probes. The electrochemical functionalization was also effective for enhancing the limit of detection in dopamine detection with the flexible SWNT electrode. The limit of detection was ∼100 nM for functionalized electrode whereas it was ∼1 μM for as-fabricated electrodes.

DOI： 10.1016/j.electacta.2018.10.147

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.electacta.2018.10.147

Language：English   Publishing type：Research paper (scientific journal)  

The simultaneous control of the number and position of negatively charged nitrogen-vacancy (NV) centers in diamond was achieved. While single near-surface NV centers are known to exhibit outstanding capabilities in external spin sensing, trade-off relationships among the accuracy of the number and position, and the coherence of NV centers have made the use of such engineered NV centers difficult. Namely, low-energy nitrogen implantation with lithographic techniques enables the nanoscale position control but results in degradation of the creation yield and the coherence property. In this paper, we show that low-energy nitrogen ion implantation to a 12C (99.95%)-enriched homoepitaxial diamond layer using nanomask is applicable to create shallow NV centers with a sufficiently long coherence time for external spin sensing, at a high creation yield. Furthermore, the NV centers were arranged in a regular array so that 40% lattice sites contain single NV centers. The XY8-k measurements using the individual NV centers reveal that the created NV centers have depths from 2 to 12 nm, which is comparable to the stopping range of nitrogen ions implanted at 2.5 keV. We show that the position-controlled NV centers are capable of external spin sensing with a ultra-high spatial resolution.

DOI： 10.1088/1367-2630/aad997

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.1088/1367-2630/aad997

Language：English   Publishing type：Research paper (scientific journal)  

Vertical-type two-dimensional hole gas diamond metal oxide semiconductor field-effect transistors
Power semiconductor devices require low on-resistivity and high breakdown voltages simultaneously. Vertical-type metal-oxide-semiconductor field-effect transistors (MOSFETs) meet these requirements, but have been incompleteness in diamond. Here we show vertical-type p-channel diamond MOSFETs with trench structures and drain current densities equivalent to those of n-channel wide bandgap devices for complementary inverters. We use two-dimensional hole gases induced by atomic layer deposited Al2O3 for the channel and drift layers, irrespective of their crystal orientations. The source and gate are on the planar surface, the drift layer is mainly on the sidewall and the drain is the p(+) substrate. The maximum drain current density exceeds 200 mA mm(-1) at a 12 mu m source-drain distance. On/off ratios of over eight orders of magnitude are demonstrated and the drain current reaches the lower measurement limit in the off-state at room temperature using a nitrogen-doped n-type blocking layer formed using ion implantation and epitaxial growth.

DOI： 10.1038/s41598-018-28837-5

Language：Others   Publishing type：Research paper (scientific journal)  

Role of Carboxyl and Amine Termination on a Boron-Doped Diamond Solution Gate Field Effect Transistor (SGFET) for pH Sensing

DOI： 10.3390/s18072178

Language：English   Publishing type：Research paper (scientific journal)  

In this paper, we report on the effect of carboxyl-and amine terminations on a boron-doped diamond surface (BDD) in relation to pH sensitivity. Carboxyl termination was achieved by anodization oxidation in Carmody buffer solution (pH 7). The carboxyl-terminated diamond surface was exposed to nitrogen radicals to generate an amine-terminated surface. The pH sensitivity of the carboxyl-and amine-terminated surfaces was measured from pH 2 to pH 12. The pH sensitivities of the carboxyl-terminated surface at low and high pH are 45 and 3 mV/pH, respectively. The pH sensitivity after amine termination is significantly higher—the pH sensitivities at low and high pH are 65 and 24 mV/pH, respectively. We find that the negatively-charged surface properties of the carboxyl-terminated surface due to ionization of –COOH causes very low pH detection in the high pH region (pH 7–12). In the case of the amine-terminated surface, the surface properties are interchangeable in both acidic and basic solutions; therefore, we observed pH detection at both low and high pH regions. The results presented here may provide molecular-level understanding of surface properties with charged ions in pH solutions. The understanding of these surface terminations on BDD substrate may be useful to design diamond-based biosensors.

DOI： 10.3390/s18072178

Language：English   Publishing type：Research paper (scientific journal)  

Electrical contact properties between carbon nanotube ends and a conductive atomic force microscope tip
Understanding the electrical contact properties of carbon nanotube (CNT) ends is important to use the high conductance of CNTs in the CNT on-axis direction in applications such as through-silicon via structures. In this study, we experimentally evaluated the contact resistivity between single-/multi-walled CNT ends and a metal nanoprobe using conductive atomic force microscopy (C-AFM). To validate the measured end contact resistivity, we compared our experimentally determined value with that obtained from numerical calculations and reported values for side contact resistivity. The contact resistivity normalized by the length of the CNT ends was 0.6-2.4 x 10(6) Omega nm for single-walled CNTs. This range is 1-2 orders of magnitude higher than that determined theoretically. The contact resistivity of a single-walled CNT end with metal normalized by the contact area was 2-3 orders of magnitude lower than that reported for the resistivity of a CNT sidewall/metal contact. For multi-walled CNTs, the measured contact resistivity was one order of magnitude higher than that of a CNT forest grown by remote plasma-enhanced chemical vapor deposition, whereas the contact resistivity of a top metal electrode was similar to that obtained for a single-walled CNT forest. Published by AIP Publishing.

DOI： 10.1063/1.5027849

Language：English   Publishing type：Research paper (scientific journal)  

The sheet resistance (R_sk) underneath ohmic Au-electrodes on hydrogen-terminated surface-conductive diamond (001) surfaces was examined by a special current-voltage measurement. It has been found that R_sk is about ~ 200 times larger than the sheet resistance, R_sh, in the open areas without Au-electrodes. The specific contact resistance, R_C, of ohmic Au-electrodes on H-terminated surface-conductive diamonds as determined by linear transmission line models must be corrected accordingly. As the results of this, R_C is suggested to be of the order of 1 × 10^{− 3} – 1 × 10^{− 4} Ωcm².

DOI： 10.1016/j.diamond.2017.09.020

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.diamond.2017.09.020

Language：English   Publishing type：Research paper (scientific journal)  

A vertical edge graphite layer (VEG) fabricated on a diamond (001) substrate and the recovery of the crystallinity of the diamond substrate following high-dose ion implantation and high-temperature annealing (HTA) was investigated. The Al ions were implanted into the diamond (001) surface at 773 K (500 °C), followed by HTA at 1973 K (1700 °C). The graphite edges were vertically oriented, but each domain was randomly rotated in the in-plane direction, which was confirmed via multiple cross-sectional transmission electron microscopy images obtained from different directions rotated 2, 5, 10, and 15° around the [001] axis. The Raman and photoluminescence exhibited no significant peaks. The initial sp² structure state of the VEG was nucleated in an early stage of the HTA and the surface diamond was subsequently reconstructed, which was confirmed using stopping-and-range-of-ions-in-matter calculations and Rutherford backscattering/channeling (RBS-C) measurements. The RBS-C spectra indicate that the crystal is maintained after hot implantation and is recovered by HTA. This VEG structure may be useful for ohmic contact with diamond electrical devices.

DOI： 10.1002/pssb.201700040

Language：English   Publishing type：Research paper (scientific journal)  

A vertical edge graphite layer (VEG) fabricated on a diamond (001) substrate and the recovery of the crystallinity of the diamond substrate following high-dose ion implantation and high-temperature annealing (HTA) was investigated. The Al ions were implanted into the diamond (001) surface at 773K (500 degrees C), followed by HTA at 1973 K (1700 degrees C). The graphite edges were vertically oriented, but each domain was randomly rotated in the in-plane direction, which was confirmed via multiple cross-sectional transmission electron microscopy images obtained from different directions rotated 2, 5, 10, and 158 around the [001] axis. The Raman and photoluminescence exhibited no significant peaks. The initial sp(2) structure state of the VEG was nucleated in an early stage of the HTA and the surface diamond was subsequently reconstructed, which was confirmed using stopping-and-range-of-ions-in-matter calculations and Rutherford backscattering/channeling (RBS-C) measurements. The RBS-C spectra indicate that the crystal is maintained after hot implantation and is recovered by HTA. This VEG structure may be useful for ohmic contact with diamond electrical devices. (C) 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

DOI： 10.1002/pssb.201700040

Language：English   Publishing type：Research paper (scientific journal)  

Diamond electrolyte solution-gate-field effect transistors (SGFETs) are suitable for applications as chemical ion sensors because of their wide potential window and good physical and chemical stabilities. In this study, we fabricated an anodically oxidized diamond SGFET from a full hydrogen-terminated diamond SGFET and demonstrated control of the device threshold voltage by irreversible anodic oxidation. The applied anodic bias voltage (V-AO) was varied gradually from low to high (1.1-1.7 V). As the anodic oxidation proceeded, the threshold voltage shifted to more negative values with no degradation of hole mobility. Thus, anodic oxidation is a useful method for controlling the threshold voltage of diamond SGFETs. Published by AIP Publishing.

DOI： 10.1063/1.4991364

Language：English   Publishing type：Research paper (scientific journal)  

Diamond electrolyte solution-gate-field effect transistors (SGFETs) are suitable for applications as chemical ion sensors because of their wide potential window and good physical and chemical stabilities. In this study, we fabricated an anodically oxidized diamond SGFET from a full hydrogen-terminated diamond SGFET and demonstrated control of the device threshold voltage by irreversible anodic oxidation. The applied anodic bias voltage (V_AO) was varied gradually from low to high (1.1-1.7 V). As the anodic oxidation proceeded, the threshold voltage shifted to more negative values with no degradation of hole mobility. Thus, anodic oxidation is a useful method for controlling the threshold voltage of diamond SGFETs.

DOI： 10.1063/1.4991364

Language：English   Publishing type：Research paper (scientific journal)  

A nitridation process of a diamond surface with nitrogen radical exposure far from the radio-frequency plasma for the stabilization of a negatively charged nitrogen-vacancy (NV%) centers near the surface is presented. At a nitrogen coverage of as high as 0.9 monolayers, high average Rabi contrasts of 0.40 + 0.06 and 0.46 + 0.03 have been obtained for single NV% centers formed by shallow nitrogen implantation with acceleration voltages of 1 and 2 keV, respectively. This indicates that nitrogen termination by a radical exposure process produces an electric charge state suitable for single NV% centers near the surface compared with the states obtained for alternatively terminated surfaces.

DOI： 10.7567/APEX.10.055503

Language：English   Publishing type：Research paper (scientific journal)  

A nitridation process of a diamond surface with nitrogen radical exposure far from the radio-frequency plasma for the stabilization of a negatively charged nitrogen-vacancy (NV%) centers near the surface is presented. At a nitrogen coverage of as high as 0.9 monolayers, high average Rabi contrasts of 0.40 +/- 0.06 and 0.46 +/- 0.03 have been obtained for single NV% centers formed by shallow nitrogen implantation with acceleration voltages of 1 and 2 keV, respectively. This indicates that nitrogen termination by a radical exposure process produces an electric charge state suitable for single NV- centers near the surface compared with the states obtained for alternatively terminated surfaces. (C) 2017 The Japan Society of Applied Physics

DOI： 10.7567/APEX.10.055503

Language：English   Publishing type：Research paper (scientific journal)  

We investigated the charge state stability and coherence properties of near-surface single nitrogen vacancy (NV) centers in 12C-enriched diamond for potential use in nanoscale magnetic field sensing applications. The stability of charge states in negatively charged NV centers (NV-) was evaluated using one of the pulsed optically detected magnetic resonance measurements, Rabi oscillation measurements. During the accumulation of Rabi oscillations, an unstable shallow NV- was converted to a neutral state. As a result, the contrast of Rabi oscillations degraded, depending on charge state stability. We stabilized the NV- state of very shallow NV centers (∼2.6 ± 1.1nm from the surface) created by 1.2 keV nitrogen ion implantation by diamond surface modification, UV/ozone exposure, and oxygen annealing. This improvement indicates that we can suppress the upward surface band bending and surface potential fluctuations through Fermi level pinning originating from oxygen-terminated diamond surfaces.

DOI： 10.7567/JJAP.56.04CK08

Language：English   Publishing type：Research paper (other academic)  

We investigated the charge state stability and coherence properties of near-surface single nitrogen vacancy (NV) centers in 12C-enriched diamond for potential use in nanoscale magnetic field sensing applications. The stability of charge states in negatively charged NV centers (NV-) was evaluated using one of the pulsed optically detected magnetic resonance measurements, Rabi oscillation measurements. During the accumulation of Rabi oscillations, an unstable shallow NV- was converted to a neutral state. As a result, the contrast of Rabi oscillations degraded, depending on charge state stability. We stabilized the NV- state of very shallow NV centers (∼2.6 ± 1.1nm from the surface) created by 1.2 keV nitrogen ion implantation by diamond surface modification, UV/ozone exposure, and oxygen annealing. This improvement indicates that we can suppress the upward surface band bending and surface potential fluctuations through Fermi level pinning originating from oxygen-terminated diamond surfaces.

DOI： 10.7567/JJAP.56.04CK08

Language：English   Publishing type：Research paper (scientific journal)  

Diamond has unique physical properties, which show great promise for applications in the next generation power devices. Hydrogen-terminated (C-H) diamond metal-oxide-semiconductor field-effect transistors (MOSFETs) often have normally-on operation in devices, because the C-H channel features a p-type inversion layer; however, normally-off devices are preferable in power MOSFETs from the viewpoint of fail safety. We fabricated hydrogen-terminated (C-H) diamond MOSFETs using a partially oxidized (partial C-O) channel. The fabricated MOSFETs showed a high breakdown voltage of over 2 kV at room temperature and normally-off characteristics with a gate threshold voltage V_th of -2.5 - 4 V.

DOI： 10.1109/LED.2017.2661340

Language：English   Publishing type：Research paper (scientific journal)  

Diamond has unique physical properties, which show great promise for applications in the next generation power devices. Hydrogen-terminated (C-H) diamond metal-oxide-semiconductor field-effect transistors (MOSFETs) often have normally-on operation in devices, because the C-H channel features a p-type inversion layer; however, normally-off devices are preferable in power MOSFETs from the viewpoint of fail safety. We fabricated hydrogen-terminated (C-H) diamond MOSFETs using a partially oxidized ( partial C-O) channel. The fabricated MOSFETs showed a high breakdown voltage of over 2 kV at room temperature and normally-off characteristics with a gate threshold voltage V-th of -2.5-- 4 V.

DOI： 10.1109/LED.2017.2661340

Language：English   Publishing type：Research paper (scientific journal)  

Complementary power field effect transistors (FETs) based on wide bandgap materials not only provide high-voltage switching capability with the reduction of on-resistance and switching losses, but also enable a smart inverter system by the dramatic simplification of external circuits. However, p-channel power FETs with equivalent performance to those of n-channel FETs are not obtained in any wide bandgap material other than diamond. Here we show that a breakdown voltage of more than 1600 V has been obtained in a diamond metal-oxide-semiconductor (MOS) FET with a p-channel based on a two-dimensional hole gas (2DHG). Atomic layer deposited (ALD) Al 2 O 3 induces the 2DHG ubiquitously on a hydrogen-terminated (C-H) diamond surface and also acts as both gate insulator and passivation layer. The high voltage performance is equivalent to that of state-of-the-art SiC planar n-channel FETs and AlGaN/GaN FETs. The drain current density in the on-state is also comparable to that of these two FETs with similar device size and V B.

DOI： 10.1038/srep42368

Language：English   Publishing type：Research paper (scientific journal)  

Complementary power field effect transistors (FETs) based on wide bandgap materials not only provide high-voltage switching capability with the reduction of on-resistance and switching losses, but also enable a smart inverter system by the dramatic simplification of external circuits. However, p-channel power FETs with equivalent performance to those of n-channel FETs are not obtained in any wide bandgap material other than diamond. Here we show that a breakdown voltage of more than 1600 V has been obtained in a diamond metal-oxide-semiconductor (MOS) FET with a p-channel based on a two-dimensional hole gas (2DHG). Atomic layer deposited (ALD) Al2O3 induces the 2DHG ubiquitously on a hydrogen-terminated (C-H) diamond surface and also acts as both gate insulator and passivation layer. The high voltage performance is equivalent to that of state-of-the-art SiC planar n-channel FETs and AlGaN/GaN FETs. The drain current density in the on-state is also comparable to that of these two FETs with similar device size and V-B.

DOI： 10.1038/srep42368

Language：English   Publishing type：Research paper (scientific journal)  

A polycrystalline boron-doped diamond (BDD) electrolyte solution-gate field effect transistor (SGFET) for use as a pH sensorwas developed. The polycrystalline diamond films with a boron-doped layer possessed semiconducting properties that were comparable to hydrogen-terminated non-doped diamond. The hydrogen-terminated BDD surface was successfully transferred to a partially oxygen-terminated surface by ozone exposure, and its SGFET current-voltage (I-V) characteristics were evaluated with bias voltages within the potential window of diamond. The drain-source current(Ids)-drain-source voltage(Vds) characteristics showed pinch-off and saturation. In addition, they stably operated in electrolyte solutions with pH values from 2 to 12. The transfer characteristics exhibited a pH sensitivity of approximately 30 mV/ pH, which is comparable with the pH sensitivity of the conventional oxygen-terminated nondoped SGFET and the single-crystal BDD SGFET investigated in our previous work. Furthermore, the BDD SGFET exhibited improved long-term stability, and the coefficient of variation (CV) of Ids for 10 months was up to 10%. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.electacta.2016.06.104

Language：English   Publishing type：Research paper (scientific journal)  

A polycrystalline boron-doped diamond (BDD) electrolyte solution-gate field effect transistor (SGFET) for use as a pH sensor was developed. The polycrystalline diamond films with a boron-doped layer possessed semiconducting properties that were comparable to hydrogen-terminated non-doped diamond. The hydrogen-terminated BDD surface was successfully transferred to a partially oxygen-terminated surface by ozone exposure, and its SGFET current–voltage (I–V) characteristics were evaluated with bias voltages within the potential window of diamond. The drain-source current(Ids)–drain-source voltage(Vds) characteristics showed pinch-off and saturation. In addition, they stably operated in electrolyte solutions with pH values from 2 to 12. The transfer characteristics exhibited a pH sensitivity of approximately 30 mV/pH, which is comparable with the pH sensitivity of the conventional oxygen-terminated non-doped SGFET and the single-crystal BDD SGFET investigated in our previous work. Furthermore, the BDD SGFET exhibited improved long-term stability, and the coefficient of variation (CV) of Ids for 10 months was up to 10%.

DOI： 10.1016/j.electacta.2016.06.104

Language：English   Publishing type：Research paper (other academic)  

More than 1600V breakdown voltages have been obtained in hydrogen terminated (C-H) diamond planar p-channel MOSFETs with gate-drain distance of 16-22 μm. The drain current density exceeds 100mA/mm in the FETs. The blocking voltage and drain current characteristics are comparable to those of n-channel AlGaN/GaN FETs and planar SiC MOSFETs in a similar device size. Atomic layer deposited Al₂O₃ works as gate insulator and passivation layer. It also induces the 2 dimensional hole gas ubiquitously on C-H diamond surface not only in planar, but in a trench gate structure. The first diamond vertical MOSFET has also operated using the trench structure.

DOI： 10.1109/ISPSD.2016.7520883

Language：English   Publishing type：Research paper (scientific journal)  

The hydrogen-terminated diamond surface (C-H diamond) has a two-dimensional hole gas (2DHG) layer independent of the crystal orientation. A 2DHG layer is ubiquitously formed on the C-H diamond surface covered by atomic-layer-deposited-Al2O3. Using Al2O3 as a gate oxide, C-H diamond metal oxide semiconductor field-effect transistors (MOSFETs) operate in a trench gate structure where the diamond side-wall acts as a channel. MOSFETs with a side-wall channel exhibit equivalent performance to the lateral C-H diamond MOSFET without a side-wall channel. Here, a vertical-type MOSFET with a drain on the bottom is demonstrated in diamond with channel current modulation by the gate and pinch off. Published by AIP Publishing.

DOI： 10.1063/1.4958889

Language：English   Publishing type：Research paper (other academic)  

More than 1600V breakdown voltages have been obtained in hydrogen terminated (C-H) diamond planar p-channel MOSFETs with gate-drain distance of 16-22 μm. The drain current density exceeds 100mA/mm in the FETs. The blocking voltage and drain current characteristics are comparable to those of n-channel AlGaN/GaN FETs and planar SiC MOSFETs in a similar device size. Atomic layer deposited Al2O3 works as gate insulator and passivation layer. It also induces the 2 dimensional hole gas ubiquitously on C-H diamond surface not only in planar, but in a trench gate structure. The first diamond vertical MOSFET has also operated using the trench structure.

DOI： 10.1109/ISPSD.2016.7520883

Language：English   Publishing type：Research paper (scientific journal)  

Understanding of the contact conductivity of carbon nanotubes (CNTs) will contribute to the further application of CNTs for electronic devices, such as thin film transistors whose channel or electrode is made of dispersed CNTs. In this study, we estimated the contact conductivity of a CNT/CNT interface from the in-plane conductivity of an uncapped CNT forest on SiC. Investigation of the electrical properties of dense CNT forests is also important to enable their electrical application. The in-plane conductivity of a dense CNT forest on silicon carbide normalized by its thickness was measured to be SO S/cm, which is two to three orders of magnitude lower than the conductivity of a CNT yarn. It was also found that both the CNT cap region and the CNT bulk region exhibit in-plane conductivity. The contact conductivity of CNTs was estimated from the in-plane conductivity in the bulk region. Dense and uncapped CNT forest can be approximated by a conductive mesh, in which each conductive branch corresponds to the CNT/CNT contact conductance. The evaluated contact conductivity was in good agreement with that calculated from the tunneling effect.

DOI： 10.1021/acs.jpcc.5b11815

Language：English   Publishing type：Research paper (other academic)  

The electrical contact properties of silicon carbide (SiC) and carbon nanotubes (CNTs) were measured by conductive atomic force microscopy (C-AFM). A CNT forest was synthesized by SiC surface decomposition. Trenches, which electrically separate the conduction area, were fabricated using a focused ion beam (FIB) without a cover layer, and the resistance of each island was measured by C-AFM. From the dependence of the resistance on the CNT forest island size, the contact resistance between the CNTs and the SiC substrate was measured. By varying the dopant density in the SiC substrate, the Schottky barrier height was evaluated to be ~0.5 eV. This is slightly higher than a previously reported result obtained from a similar setup with a metal covering the CNT forest. We assumed that the damaged region existed in the islands, which is due to the trench formation by the FIB. The commensurate barrier height was obtained with the length of the damaged region assumed to be ~3 μm. Here, we could estimate the resistivity of a CNT/SiC interface without a cover layer. This indicates that a CNT forest on SiC is useful as a brief contact electrode.

DOI： 10.4028/www.scientific.net/MSF.858.561

Language：English   Publishing type：Research paper (scientific journal)  

Large-current-controllable carbon nanotube field-effect transistors (CNT-FETs) were fabricated with mm-long CNT sheets. The sheets, synthesized by remote-plasma-enhanced CVD, contained both single- and double-walled CNTs. Titanium was deposited on the sheet as source and drain electrodes, and an electrolyte solution was used as a gate electrode (solution gate) to apply a gate voltage to the CNTs through electric double layers formed around the CNTs. The drain current came to be well modulated as electrolyte solution penetrated into the sheets, and one of the solution gate CNT-FETs was able to control a large current of over 2.5 A. In addition, we determined the transconductance parameter per tube and compared it with values for other CNT-FETs. The potential of CNT sheets for applications requiring the control of large current is exhibited in this study.

DOI： 10.1063/1.4921454

Language：English   Publishing type：Research paper (scientific journal)  

Large-current-controllable carbon nanotube field-effect transistors (CNT-FETs) were fabricated with mm-long CNT sheets. The sheets, synthesized by remote-plasma-enhanced CVD, contained both single-and double-walled CNTs. Titanium was deposited on the sheet as source and drain electrodes, and an electrolyte solution was used as a gate electrode (solution gate) to apply a gate voltage to the CNTs through electric double layers formed around the CNTs. The drain current came to be well modulated as electrolyte solution penetrated into the sheets, and one of the solution gate CNT-FETs was able to control a large current of over 2.5 A. In addition, we determined the transconductance parameter per tube and compared it with values for other CNT-FETs. The potential of CNT sheets for applications requiring the control of large current is exhibited in this study. (C) 2015 AIP Publishing LLC.

DOI： 10.1063/1.4921454

Language：English   Publishing type：Research paper (scientific journal)  

Electrical contacts to silicon carbide with low contact resistivity and high current durability are crucial for future SiC power devices, especially miniaturized vertical-type devices. A carbon nanotube (CNT) forest formed by silicon carbide (SiC) decomposition is a densely packed forest, and is ideal for use as a heat-dissipative ohmic contact in SiC power transistors. The contact resistivity and Schottky barrier height in a Ti/CNT/SiC system with various SiC dopant concentrations were evaluated in this study. Contact resistivity was evaluated in relation to contact area. The Schottky barrier height was calculated from the contact resistivity. As a result, the Ti/CNT/SiC contact resistivity at a dopant concentration of 3 x 10(18) cm(-3) was estimated to be similar to 1.3 x 10(-4) Omega cm(2) and the Schottky barrier height of the CNT/SiC contact was in the range of 0.40-0.45 eV. The resistivity is relatively low for SiC contacts, showing that CNTs have the potential to be a good ohmic contact material for SiC power electronic devices. (C) 2015 AIP Publishing LLC.

DOI： 10.1063/1.4916248

Event date： 2024.3 - 2023.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：徳島大学常三島キャンパス, 徳島県徳島市   Country：Japan  

Event date： 2024.3

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2024.3

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

researchmap

Event date： 2023.11

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：オンライン   Country：Japan  

Event date： 2023.11

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

researchmap

Event date： 2023.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Keio Plaza Hotel, Sapporo, Hokkaido   Country：Japan  

Event date： 2023.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東海大学湘南キャンパス, 神奈川県平塚市   Country：Japan  

Event date： 2023.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東海大学湘南キャンパス, 神奈川県平塚市   Country：Japan  

Event date： 2023.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東海大学湘南キャンパス, 神奈川県平塚市   Country：Japan  

Event date： 2023.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東海大学湘南キャンパス, 神奈川県平塚市   Country：Japan  

Event date： 2023.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：熊本城ホール, 熊本県熊本市   Country：Japan  

Event date： 2023.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：熊本城ホール, 熊本県熊本市   Country：Japan  

Event date： 2023.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Waseda University, Shinjuky-ku, Toky   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：熊本城ホール, 熊本県熊本市   Country：Japan  

Event date： 2023.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Palau de Congressos de Palma, Mallorca   Country：Spain  

Event date： 2023.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Palau de Congressos de Palma, Mallorca   Country：Spain  

Event date： 2023.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Palau de Congressos de Palma, Mallorca   Country：Spain  

Event date： 2023.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Palau de Congressos de Palma, Mallorca   Country：Spain  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue： 崇城大学, 熊本県熊本市   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue： 崇城大学, 熊本県熊本市   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue： 崇城大学, 熊本県熊本市   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue： 崇城大学, 熊本県熊本市   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue： 崇城大学, 熊本県熊本市   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue： 崇城大学, 熊本県熊本市   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue： 崇城大学, 熊本県熊本市   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：西新プラザ, 福岡県福岡市   Country：Japan  

Event date： 2023.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Busan   Country：Korea, Republic of  

Event date： 2023.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：上智大学四谷キャンパス, 東京都千代田区   Country：Japan  

Event date： 2023.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋大学東山キャンパス, 愛知県名古屋市   Country：Japan  

Event date： 2023.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋大学東山キャンパス, 愛知県名古屋市   Country：Japan  

Event date： 2023.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋大学東山キャンパス, 愛知県名古屋市   Country：Japan  

Event date： 2023.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京工業大学大岡山キャンパス, 東京都目黒区   Country：Japan  

Event date： 2022.12

Language：English   Presentation type：Oral presentation (general)  

Venue：産業貿易センター，神奈川県横浜市   Country：Japan  

Event date： 2022.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：慶應義塾大学矢上キャンパス, 神奈川県横浜市   Country：Japan  

Event date： 2022.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：慶應義塾大学矢上キャンパス, 神奈川県横浜市   Country：Japan  

Event date： 2022.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：アスティとくしま, 徳島県徳島市   Country：Japan  

Event date： 2022.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：THE KASHIHARA, 奈良県橿原市   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東北大学川内北キャンパス, 宮城県仙台市   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東北大学川内北キャンパス, 宮城県仙台市   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東北大学川内北キャンパス, 宮城県仙台市   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福井大学文京キャンパス, 福井県福井市   Country：Japan  

Event date： 2022.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Kanazawa Bunka Hall, Kanazawa   Country：Japan  

Event date： 2022.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Kanazawa Bunka Hall, Kanazawa   Country：Japan  

Event date： 2022.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Kanazawa Bunka Hall, Kanazawa   Country：Japan  

Event date： 2022.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2022.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2022.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2022.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2022.1

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2022.1

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：Online   Country：Japan  

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.1

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.1

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2021.1

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2020.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2020.10

Language：English   Presentation type：Oral presentation (general)  

Venue：Online   Country：Japan  

Event date： 2020.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2020.9

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Japan  

Event date： 2020.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京電機大学北千住キャンパス   Country：Japan  

Event date： 2020.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京電機大学北千住キャンパス   Country：Japan  

Event date： 2020.3

Language：English   Presentation type：Oral presentation (general)  

Venue：東京電機大学北千住キャンパス   Country：Japan  

Event date： 2020.1

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：三菱電機健康保険組合 湯布郷館, 大分県由布市湯布院町   Country：Japan  

Event date： 2020.1

Language：English   Presentation type：Oral presentation (general)  

Venue：三菱電機健康保険組合 湯布郷館, 大分県由布市湯布院町   Country：Japan  

Event date： 2019.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：アクトシティ浜松 （静岡県浜松市）   Country：Japan  

Event date： 2019.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京工業大学（東京都目黒区）   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州工業大学 戸畑キャンパス, 福岡県北九州市   Country：Japan  

Event date： 2019.9

Language：English   Presentation type：Oral presentation (general)  

Venue：九州工業大学 戸畑キャンパス, 福岡県北九州市   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州工業大学 戸畑キャンパス, 福岡県北九州市   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州工業大学 戸畑キャンパス, 福岡県北九州市   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州工業大学 戸畑キャンパス, 福岡県北九州市   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州工業大学 戸畑キャンパス, 福岡県北九州市   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州工業大学 戸畑キャンパス, 福岡県北九州市   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州工業大学 戸畑キャンパス, 福岡県北九州市   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州工業大学 戸畑キャンパス, 福岡県北九州市   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：九州工業大学 戸畑キャンパス, 福岡県北九州市   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学札幌キャンパス(北海道札幌市)   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：広島県広島市、広島工業大学五日市キャンパス   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：岩⼿⼤学上⽥キャンパス (岩⼿県盛岡市)   Country：Japan  

Event date： 2019.7

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京工業大学すずかけ台キャンパス, 神奈川県横浜市   Country：Japan  

Event date： 2019.7

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京工業大学すずかけ台キャンパス, 神奈川県横浜市   Country：Japan  

Type：Competition, symposium, etc. 

Type：Competition, symposium, etc. 

Type：Peer review 

Number of peer-reviewed articles in foreign language journals：7

Type：Competition, symposium, etc. 

Type：Competition, symposium, etc. 

Audience：Infants,　Schoolchildren,　Junior students,　High school students

Type：Other