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Background: Combined effects of physical activity (PA) and passive/mentally active sedentary behavior (SB) on dementia are unclear. Purpose: Identifying the effects of these behaviors on dementia onset among older adults. Methods: All residents aged ���65 in Tsuru, Yamanashi, Japan, were enrolled. A mail survey was conducted in 2016. Respondents were followed up for five years, and 5323 participants were included in the analyses (79.7%). Dementia onset was examined using long-term care insurance data. PA was evaluated with the International Physical Activity Questionnaire and categorized into, The Health & Fitness Journal of Canada, Vol. 14 No. 3 (2021): Proceedings from the 8th International Society for Physical Activity and Health Congress

Wide bandgap semiconductors are increasingly important for bioimaging applications, as they can possess good biocompatibility and host a large range of fluorescent defects spanning the visible to infrared. Gallium nitride is one promising host for photostable fluorophores. In particular, neodymium (Nd)-doped gallium nitride (GaN) shows bright near infrared fluorescence and narrow room temperature linewidth and is therefore a candidate material for fluorescent probes for bioimaging. To explore the conditions necessary to generate biomarkers based on Nd:GaN, this paper reports the room temperature photoluminescence (PL) properties of small ensembles of Nd ions implanted into nanoscale regions of GaN epilayers. The minimum volume of Nd-implanted GaN which can be optically detected in this study is about 8E+4 nm^3 and the minimum detected ensemble of Nd ions is about 4E3, although not all of implanted Nd ions activate as luminescence centers. We show from the PL excitation spectra that the strongest resonant excitation appears at 619 nm, attributed to the 4I9/2 → 4G5/2 (4G7/2) transition in the 4f-shell. We measure the luminescence lifetime to be several tens of microseconds. We also identify the presence of a different excitation mechanism from the resonant excitation when excited below 510 nm (above 2.43 eV).

Spin defects of which states can be manipulated in Silicon Carbide (SiC) have drawn considerable attention because of their applications to quantum technologies. The single negatively-charged pairs of VSi and nitrogen atom (N) on an adjacent C site (NcVsi- center) in SiC is suitable for them. This paper reports the formation of NcVsi- centers on 4H-SiC epilayers with different nitrogen concentrations using light/heavy ion irradiation and subsequent thermal annealing. The formation of NcVsi- centers is characterized by the near infrared photoluminescence (PL) spectroscopy. It is shown that the PL intensity from NcVsi- centers depends on the N concentration and the ion irradiation conditions. The PL intensity increases monotonically with increasing the N concentration when the N concentration is above 2.6×10^16 cm^-3 , whereas no linear correlation between them does not appear below that N concentration. Although the PL intensity increases with increasing defects induced by ion irradiation, the PL quenching due to neighboring residual defects appear at above the areal vacancy concentration of 10^17 vac/cm^2 and the broad Raman scattering spectra originated from vibration modes of amorphized regions hinder the PL from NcVsi- centers at above 10^18 vac/cm^2. The formation mechanism and the charge state stability of NcVsi- centers are discussed based on the obtained results.

This paper reports optical properties of negatively charged NcVsi- centers in silicon carbide (a nitrogen substituting for a carbon atom adjacent to a silicon vacancy) whose emission wavelength is 1100-1500 nm at room temperature. High-purity semi-insulating (HPSI) 4H-SiCs are implanted with high energy N ion beams and subsequently thermally annealed to form NcVsi- centers. We investigated a wide range of N ion implantation dose using a micro ion beam implantation technique and observed the photoluminescence intensity from the SiC-NV centers. We show that under conditions of heavy implantation, the excitation laser power excites residual defects and their fluorescences interferes with the emission from the NcVsi- centers. These results allow us to clarify the requirements to optically detect isolated single NcVsi- centers at lightly implanted conditions.

Single-photon sources and their optical spin readout are at the core of applications in quantum communication, quantum computation, and quantum sensing. Their integration in photonic structures such as photonic crystals, microdisks, microring resonators, and nanopillars is essential for their deployment in quantum technologies. While there are currently only two material platforms (diamond and silicon carbide) with proven single-photon emission from the visible to infrared, a quantum spin–photon interface, and ancilla qubits, it is expected that other material platforms could emerge with similar characteristics in the near future. These two materials also naturally lead to monolithic integrated photonics as both are good photonic materials. While so far the verification of single-photon sources was based on discovery, assignment and then assessment and control of their quantum properties for applications, a better approach could be to identify applications and then search for the material that could address the requirements of the application in terms of quantum properties of the defects. This approach is quite difficult as it is based mostly on the reliability of modeling and predicting of color center properties in various materials, and their experimental verification is challenging. In this paper, we review some recent advances in an emerging material, low-dimensional (2D, 1D, 0D) hexagonal boron nitride (h-BN), which could lead to establishing such a platform. We highlight the recent achievements of the specific material for the expected applications in quantum technologies, indicating complementary outstanding properties compared to the other 3D bulk materials.

Since Rare-Earth (RE) doped Gallium Nitride (GaN) is expected to be used as electrically driven single photon source at room temperature, low dose RE-ion implantation and their activation as luminescent centers are of interest. This paper reports photoluminescence (PL) properties of Praseodymium (Pr) implanted GaN at different temperatures ranging from room temperature to 1200 °C. All the Pr-implanted GaN samples are thermally annealed after implantation and show strong PL emissions at 650.2 nm and 652.0 nm, originated from 3P0→3F2 transition in 4f-shell of Pr3+ ions. It is shown that the PL intensity originating from Pr3+ ions is reduced as the implantation temperature increases for the Pr-implanted samples annealed at 1200 °C. This result suggests that Pr3+ ions quench due to the formation of complex defects and defect clusters. The effect of high temperature implantation on the recovery of GaN crystallinity is discussed in terms of critical dose and displacement damage.

Organic solar cells have attractive potential for space applications as they have very high specific power (power generated per weight) and ultra-high flexibility (to reduce stowed volume). However, one critical issue is whether they are stable under the harsh space environment, particularly their stability under high energy, high flux, electron and proton bombardment. In this paper, the stability of benchmark organic photovoltaic layers under proton bombardment (150 keV with a fluence of 1E12 /cm2) and electron bombardment (1MeV with a fluence of 1E13 /cm2) unde vacuum is investigated. Raman spectroscopy, Photoluminescence spectroscopy, and optical reflectance spectroscopy are applied to study their chemical/structural, photo-chemical/morphological, and optical stability after the bombardments. The results show that all the benchmark organic photovoltaic films are stable under the radiation, implying that organic solar cells could be feasible for space applications.

We fabricated circular- and square-shaped pillar arrays with sizes ranging from 100 nm to 2 µm on Pr-implanted GaN epilayers using electron beam lithography, metal deposition, and dry etching techniques. The implantation energy and dose were 100 keV and 1.3×1014 cm-2, respectively. The peak implanted region was estimated to be 24 nm from the top of pillars according to the Monte Carlo simulation code TRIM, and the pillar length was measured to be 510 nm by scanning electron microscopy. Intensity of two emission peaks at 650 nm and 652 nm, which were attributed to 3P0-3F2 transition in the 4f-shell, was analyzed by a home build confocal microscopy. It was shown that the photon emission intensity from Pr3+ ions strongly depended on the nanopillar structures and sizes, and the enhancement more than 20-fold was achieved compared to the non-structured region. The luminescence lifetime was independent of nanopillar structures and sizes. These results indicate that the absorption efficiency of incident photons and the photon extraction efficiency were enhanced by the confinement in nanopillars., 4th QST International Symposium

窒化ガリウム半導体(GaN)中の孤立したランタノイドは、室温でも狭い線幅で高輝度の発光を示すことから、単一光子源への応用が期待できる。Prイオン注入したGaN上に様々なサイズのナノピラー構造を形成し、ピラー中Pr3+の3P0 → 3F2遷移に起因する652 nm付近の発光を室温で観察したところ、ピラー構造を持たないGaN中Pr3+よりも高い発光強度を得た。本講演では、励起光強度依存性や発光遷移寿命と併せてそのメカニズムについて議論する。, 第67回応用物理学会春季学術講演会

Lanthanoid (Ln)-doped Gallium Nitride (GaN) have attracted attentions because of their high intensity luminescence and sharp room-temperature (RT) optical linewidth. These superior luminescent properties are quite attractive for the application of single photon source (SPS) which is a key technology for quantum computing, quantum sensing, and quantum key distribution. However, one of the challenges to realize Ln-doped GaN SPS is the long luminescent transition lifetime, resulting in the low photon counts insufficient to optically detect isolated single Ln ions. Confinement of luminescent centers into nanometersized regions is an effective method to enhance their photon emission and we here we show that confinement into GaN nanopillars enhances photon emission from implanted praseodymium (Pr) ions at RT., The 8th International Conference on Nanoscience and Nanotechnology (ICONN2020)

Introduction Nitrogen-vacancy (NV) centers in diamond are promising solid-state quantum sensors. The sensor can potentially monitor the real-time magnetic field at room-temperature toward the brain-machine interface. One of the biggest challenges is to implement a highly sensitive sensor in a compact system. There are two major ways to achieve it. An analog signal processing method with a lock-in amplifier is fast to obtain the signal, but it increases the size of the sensor system. The digital signal processing method with the Fourier transform is simple, but it needs more computational resources. Reducing computational resources with the simple system is an important task for monitoring a real-time magnetic field. In this study, we demonstrate an alternative method of digital signal processing with less computational resources than the Fourier transform. The computational time of the method to compute the signal from n points of data is O(n), whereas the time with Fourier transform is O(n log n). Method and Result We confirm our method with a large detection volume of the ensemble NV centers. The microwave and optical systems used in our experiment are shown in Fig. 1. The diamond sample containing NV centers was placed between the microwave resonator and a compound parabolic concentrator1. We used a coplanar waveguide resonator (CWR) with a wide center electrode for strong and uniform microwave irradiation2. The power of microwave with frequency modulation is 25 dBm before the CWR. The 300 mW laser beam to the diamond was focused with a beam diameter of about 30 μm. The fluorescence from the NV centers was collected through the compound parabolic concentrator and detected using a photodiode. The detected signal of the photodiode is analyzed by digital signal processing. The method obtains the result using a digital filter that effectively becomes a sinc filter using the orthogonality of trigonometric functions by multiplication of the acquired data by a trigonometric function. Figures 2 shows continuous-wave optical detected magnetic resonance (CW-ODMR) spectrum using the digital signal processing with a different modulation frequency of the microwave. The maximum slope and the noise of the signal become smaller with increasing the modulation frequency for different reasons. The low transition rate between quantum states of the NV center reduces the maximum slope for high modulation frequency. While the noise becomes smaller for high modulation frequency. We evaluate the maximum signal slope (Fig. 3) and noise level of the spectrum (Fig. 4). We found the reduction of the noise is greater than the reduction of the maximum slope. This work was supported by MEXT Quantum Leap Flagship Program (MEXT Q-LEAP) Grant Number JPMXS0118067395., The 2nd International Forum on Quantum Metrology and Sensing への出席

Recently, NCVSi- centers in silicon carbide (SiC), i.e. negatively-charged pairs of silicon vacancy (VSi) and nitrogen (N) atom on an adjacent carbon (C) site, have attracted attention as they are an optically active defect with an electronic structure strongly resembling that of NV centers in diamond. The emission wavelength of NCVSi- centers is around 1300 nm at room temperature (RT) which is advantageous for in-vivo imaging and sensing (temperature, magnetic field, etc.), since the near-infrared (NIR) light can penetrate biological tissues efficiently than visible light. Although NCVSi- centers are known to be formed by charged particle bombardment and subsequent thermal annealing, fundamental optical properties are less well understood. In this study, we clarified the luminescence lifetime and saturation behavior of photon emisstion, and their excitation wavelength dependence., The 2nd International Forum on Quantum Metrology and Sensing (IFQMS)

太陽電池の放射線照射効果の解明は、宇宙用太陽電池の軌道上劣化予測や、放射線耐性向上の実現において重要である。短絡電流（Isc）低下に影響する拡散長の放射線損傷は先行研究によって明らかになっており、この知見は宇宙用太陽電池の設計に反映されている。そのため、現在宇宙用太陽電池として主流の3接合太陽電池では、Iscの劣化量は少なく、放射線による出力低下は電圧劣化の影響が支配的である。更なる放射線耐性向上を実現するためには、電圧劣化を決定する非発光再結合寿命に関する放射線損傷の解明が求められる。しかし、非発光再結合寿命に関する放射線損傷は、電界が印加されている空乏領域と印加されていない中性領域において異なることが示唆されており、その定量的な分離は従来の解析手法では困難であった。そこで我々は、空乏領域と中性領域における非発光再結合寿命を得るための解析手法を提案し、それを放射線照射前後の3接合太陽電池に適用することで、各領域における非発光再結合寿命に関する放射線損傷を調べた。, QST高崎サイエンスフェスタ2019

炭化ケイ素(SiC)半導体における電子を1個捕獲した窒素・空孔複合欠陥(NCVSi-)は、スピン量子数S = 1を有し、生体透過性が極めて高い1300 nm付近の発光を室温で示すことから、生命科学や医療分野における量子センシング（局所領域の高感度磁場・温度計測）への応用が期待されている。NCVSi-は量子ビーム照射とその後の高温熱処理によって形成されることがわかっており、発光スペクトルの温度依存性やゼロフォノン線(ZPL)の同定がなされている。しかし、量子センシングの実現にあたっては、発光スペクトルのみならず、発光遷移寿命や励起光波長依存性等、詳細な発光特性を明らかにする必要があるため、NCVSi-の光学特性を詳細に明らかにした。, QST高崎サイエンスフェスタ2019

4H-SiC中における電子を1個捕獲した窒素・空孔複合欠陥（SiC-NVセンター）は量子センサとしての応用が期待されているが、その効率的な形成条件については明らかになっていない。本研究では、不純物窒素濃度が異なる4H-SiCエピタキシャル膜に対し、様々な条件でのイオンビーム照射を行い、室温および80 Kでのフォトルミネッセンス測定を行い、SiC-NVセンターの形成量を評価した。その結果、不純物窒素濃度、欠陥導入量の変化によるSiC-NVセンター起因の発光強度の変化を系統的に明らかにすることができた。, 先進パワー半導体分科会 第6回講演会

SiC結晶中シリコン空孔(VSi)の光検出磁気共鳴(ODMR)信号にアニール温度が及ぼす影響を調べた。600 °Cでのアニール後、ODMR信号コントラストは最大となった。アニールに対する欠陥の振る舞いと欠陥準位より、EH3センターといった他の欠陥の減少がコントラストの増加に寄与したと考えられる。, 先進パワー半導体分科会 第6回講演会

粒子ビーム描画(PBW)を用いてSiC pnダイオード内に作製した3 次元配列Vsiを用いて、光・電気同時励起時におけるVsiの光学特性を調べた。小電流印加で発光量、光検出磁場共鳴(ODMR)スペクトルのコントラストが共に劣化した。光・電気励起は同時に起きない発光メカニズムモデルを用いたシミュレーションは発光量変化をよく再現した。, 先進パワー半導体分科会 第6回講演会

Lanthanoid-doped gallium nitride (GaN) semiconductors have attracted attention because of their high intensity luminescence and sharp room-temperature (RT) optical linewidth. GaN surfaces can be chemically functionalized and nanometer-sized particles are available, opening the door to lifescience applications such as bioimaging and biosensing. Neodymium (Nd)-doped GaN is of strong interest due to its strong near infrared luminescence at 0.9~1.1 µm which is suitable for optical imaging in biological tissues. To realize bioimaging/sensing using Nd-doped GaN nanoparticles, the small ensemble of Nd ions has to be optically detected at RT with high contrast. This paper reports photoluminescence of Nd ions implanted into submicron regions of GaN epilayer and their luminescence properties at RT. The Nd implanted square regions with the side of 250 nm were optically detected. The minimum size which was successfully fabricated and optically detected was 150 nm in this study, which supports further investigations into fluorescent nanoparticles for bioimaging applications. In the presentation, PL spectra, PL excitation spectra, saturation behavior, and luminescent transition lifetime at RT will be discusse, 29th Annual Meeting of MRS-J

In this study, we investigate the photoluminescence (PL) properties of implanted Praseodymium (Pr) ions into GaN at temperatures up to 1200 oC to clarify the effect of implantation temperature on the Pr3+ activation., 23rd International Workshop on Inelastic Ion-Surface Collisions

We investigated optical properties, luminescence intensity and optically detected magnetic resonance (ODMR) signal, of three dimensionally (3D) arrayed VSis upon simultaneous optically and electrically excitation. The results showed that transited conducting electrons disturb photoexcitation and ODMR by Pauli exclusion principle, which degrades optical properties of VSi under simultaneous excitation., International Conference on Silicon Carbide and Related Materials

We investigated the effect of nitrogen concentration of 4H-SiC epilayer on the near-infrared (NIR) photoluminescence (PL) intensities from nitrogen-vacancy (NV) centers and found that the NIR-PL emission increased with increasing N concentration. It can be concluded that the effects of irradiation fluence on PL intensity of NV centres in SiC strongly depends on the primary N concentration., International Conference on Silicon Carbide and Related Materials 2019

We demonstrated the enhancement of the optically detected magnetic resonance (ODMR) contrast of negatively charged silicon vacancy (VSi-) in SiC by thermal treatment. To create high density VSi-, Proton Beam Writing (PBW) was conducted. After an annealing at 600 °C, ODMR contrast showed the highest value in the investigated temperature range. At a fewer irradiation fluence, despite no significant change was observed in terms of VSi- PL intensity, the improvement of the ODMR contrast was observed. Considering defect energy levels and annealing behavior previously reported, it was deduced that the improvement of the ODMR contrast was caused by the reduction of other irradiation induced defect centers, such as EH1/EH3 centers., International Conference on Silicon Carbide and Related Materials

We present a study of electrically active radiation-induced defects formed in 4H-SiC epitaxial layers following irradiation with fast neutrons, as well as 600 keV H+ and 2 MeV He++ ion implantations. We also look at electron emission energies and mechanisms of the carbon vacancy in 4H-SiC by means of first-principles modelling. Combining the relative stability of carbon vacancies at different sites with the relative amplitude of the observed Laplace-DLTS peaks, we were able to connect Z1 and Z2 to emissions from double negatively charged carbon vacancies located at the h- and k-sites, respectively.

4H-SiC pin-diodes are fabricated and the surface SPSs formed in the pin diodes are investigated using a confocal laser scanning fluorescence microscope (CFM). Locations where the surface SPSs appear as well as photoluminescence spectra of the observed surface SPSs are presented. Antibunching characteristics of the surface SPSs are also investigated by the second order autocorrelation function measurement. We conclude that two different types of surface SPSs appear in the surface of 4H-SiC. The location dependence of the observed surface SPSs indicates that the oxide layer on 4H-SiC plays an important role in the formation of surface SPSs, whereas neither ion implantation nor donor ions had an effect. The peak wavelength of luminescence spectra widely varies depending on their locations, indicating lattice strain introduced by the oxide layer has the potential to affect the luminescence spectra.