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Materials Sciences and Applications 2015年第7期6卷 676-680页

作者： kenta miura Yuki Arai Osamu Hanaizumi Graduate School of Science and Technology Gunma University Kiryu Japan

In this paper, we report on the first observation of blue-light emission bands from europium-doped tantalum pentoxide (Ta2O5:Eu) thin films prepared using a simple co-sputtering method. We prepared four specimens from one as-deposited sample, and we subsequently annealed them at 700°C, 800°C, 900°C, or 1000°C for 20 min. Four remarkable photoluminescence (PL) peaks at wavelengths of 600, 620, 650, and 700 nm due to the 5D0→7F1, 5D0→7F2, 5D0→7F3, and 5D0→7F4 transitions of Eu3+ were observed from all the specimens, and blue PL peaks around a wavelength of 450 nm were also observed from the specimens annealed at 800°C, 900°C, and 1000°C. The blue PL peaks seem to be originated from the 4f65d1→4f7 transition of Eu2+. Both Eu3+ and Eu2+ ions seem to exist in our Ta2O5:Eu co-sputtered thin films annealed at temperatures from 800°C to 1000°C. Such Ta2O5:Eu co-sputtered thin films seem to be used as multi-functional coating films having both anti-reflection and down-conversion effects for realizing high-efficiency silicon solar cells.

关键词： Ta2O5 Eu Co-Sputtering Blue-Light Emission Band

Photoluminescence Properties of Europium and Cerium Co-Doped Tantalum-Oxide Thin Films Prepared Using Co-Sputtering Method

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Journal of Materials Science and Chemical Engineering 2015年第8期3卷 30-34页

作者： kenta miura Tetsuhito Suzuki Osamu Hanaizumi Graduate School of Science and Technology Gunma University Kiryu Japan

We fabricated europium and cerium co-doped tantalum (V) oxide (Ta2O5: Eu, Ce) thin films using our co-sputtering method for the first time, and evaluated photoluminescence (PL) properties of the films after annealing at 600°C - 1100°C for 20 min. Four remarkable PL peaks at wavelengths of 600, 620, 700, and 705 nm were observed from the film annealed at 900°C. The intensities of the 700- and 705-nm peaks due to the 5D0 → 7F4 transition of Eu3+ were much stronger than those of the 600-nm (5D0 → 7F1) and 620-nm (5D0 → 7F2) peaks of the film annealed at 900°C. It seems that energy transfer from Ce3+ to Eu3+ occurs in the film, and much energy is selectively used for the 5D0 →7F4 and 5D0 →?7F1?transitions. Such a Ta2O5: Eu, Ce co-sputtered thin film seems to be used as a multi-functional coating film having both anti-reflection and down-conversion effects for realizing a high-efficiency silicon solar cell.

关键词： Tantalum Oxide Europium Cerium Co-Sputtering Photoluminescence

Observation of Violet-Light Emission Band for Thulium-Doped Tantalum-Oxide Films Produced by Co-Sputtering

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Materials Sciences and Applications 2015年第7期6卷 656-660页

作者： kenta miura Tetsuhito Suzuki Osamu Hanaizumi Graduate School of Science and Technology Gunma University Kiryu Japan

We prepared thulium-doped tantalum (V) oxide (Ta2O5:Tm) thin films using co-sputtering of two Tm2O3 pellets and a Ta2O5 disc, and we observed photoluminescence (PL) peaks not only around a wavelength of 800 nm due to the 3H4→3H6 transition of Tm3+ but also around a wavelength of 400 nm (violet) from the films after annealing for the first time. Comparatively narrow PL peaks around the wavelength of 400 nm were observed from the films annealed at 800°C and 900°C for 20 min. The peak intensity from the film annealed at 900°C was approximately four-times stronger than that from the film annealed at 800°C. The origin of the 400-nm peaks seems to be the same as our non-doped Ta2O5 thin films deposited using radio-frequency sputtering because we observe PL peaks around 400 - 430 nm from the Ta2O5 films. Such a Ta2O5:Tm co-sputtered thin film seems to be used as a multi-functional coating film having both anti-reflection and down-conversion effects for realizing a high-efficiency silicon solar cell.

关键词： Tantalum Oxide Thulium Co-Sputtering Violet-Light Emission Band

Regularizing fuel-optimal multi-impulse trajectories

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Astrodynamics 2024年第1期8卷 97-119页

作者： kenta Oshima Department of Mechanical Systems Engineering Hiroshima Institute of TechnologyHiroshima731-5193Japan

The regularization theory has successfully enabled the removal of gravitational singularities associated with celestial *** this study,regularizing techniques are merged into a multi-impulse trajectory design framework that requires delicate computations,particularly for a fuel minimization *** variables based on the Levi–Civita or Kustaanheimo–Stiefel transformations express instantaneous velocity changes in a gradient-based direct optimization *** formulation removes the adverse singularities associated with the null thrust impulses from the derivatives of an objective function in the fuel minimization *** favorite singularity-free property enables the accurate reduction of unnecessary impulses and the generation of necessary impulses for local optimal solutions in an automatic *** of fuel-optimal multi-impulse trajectories are presented,including novel transfer solutions between a near-rectilinear halo orbit and a distant retrograde orbit.

关键词： regularization trajectory optimization fuel minimization multi-impulse trajectory

Fabrication of Erbium and Ytterbium Co-Doped Tantalum-Oxide Thin Films Using Radio-Frequency Co-Sputtering

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Materials Sciences and Applications 2015年第5期6卷 343-347页

作者： kenta miura Yuki Arai Kazusa Kano Osamu Hanaizumi Graduate School of Science and Technology Gunma University Kiryu Japan

An erbium and ytterbium co-doped tantalum-oxide (Ta2 O5:Er, Yb) thin film was fabricated using a simple co-sputtering method for the first time, and its photoluminescence (PL) spectrum was evaluated. Energy transfers between Er3+ and Yb3+ in the Ta2 O5:Er, Yb co-sputtered thin film were discussed by comparing between PL spectra of the Ta2 O5:Er, Yb film and Ta2 O5:Er or Ta2 O5:Yb films reported in our previous works. Such a Ta2 O5:Er, Yb co-sputtered film can be used as a high-refractive- index and light-emitting material of a multilayered photonic crystal that can be applied to a novel light-emitting device, and it will also be used as a multi-functional coating film having both anti-reflection and down-conversion effects for realizing a high-efficiency silicon solar cell.

关键词： Tantalum Oxide Erbium Ytterbium Co-Sputtering Photoluminescence

Preparation of Light-Emitting Ytterbium-Doped Tantalum-Oxide Thin Films Using a Simple Co-Sputtering Method

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Materials Sciences and Applications 2015年第2期6卷 209-213页

作者： kenta miura Kazusa Kano Yuki Arai Osamu Hanaizumi Graduate School of Science and Technology Gunma University Kiryu Japan

Light-emitting ytterbium-doped tantalum-oxide thin films were prepared using a simple co-sputtering method for the first time. Sharp photoluminescence peaks having a wavelength of around 980 nm were observed from films annealed from 700°C to 1000°C for 10 to 40 min. The strongest intensity of the 980-nm peak was obtained from a film deposited using three ytterbium-oxide pellets and annealed at 800°C for 20 min. Such rare-earth doped tantalum-oxide sputtered films can be used as high-refractive-index materials of autocloned photonic crystals that can be applied to novel light-emitting devices, and they will also be used as both anti-reflection and down-conversion layers for realizing high-efficiency silicon solar cells.

关键词： Tantalum Oxide Ytterbium Co-Sputtering Annealing Photoluminescence

Effects of Si-Layer-Thickness Ratio on UV-Light-Emission Intensity from Si/SiO2Multilayered Thin Films Prepared Using Radio-Frequency Sputtering

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Materials Sciences and Applications 2015年第3期6卷 215-219页

作者： kenta miura Hitomi Hoshino Masashi Honmi Osamu Hanaizumi Graduate School of Science and Technology Gunma University Kiryu Japan

We investigated the effects of Si-layer-thickness ratios on ultraviolet (UV) peak intensities of Si/ SiO2 multilayered films produced by alternately stacking several-nanometer-thick Si and SiO2 layers using radio-frequency sputtering for the first time. The Si-layer-thickness ratio of the Si/SiO2 film is a very important parameter for enhancing the peak intensity because the ratio is concerned with the size of Si nanocrystals in the film, which might affect the intensity of the UV light emission from the film. We prepared seven samples with various estimated Si-layer-thickness ratios, and measured the photoluminescence spectra of the samples after annealing at 1150°C, 1200°C, or 1250°C for 25 min. From our experiments, we estimate that the proper Si-layer-thickness ratio to obtain the strongest UV peaks from the Si/SiO2 multilayered films is around 0.29. Such a UV-lightemitting thin film is expected to be used in future higher-density optical-disk systems.

关键词： Si SiO2 Multilayer Sputtering UV-Light Emission

Photoluminescence Properties of Thulium and Cerium Co-Doped Tantalum-Oxide Films Prepared by Radio-Frequency Co-Sputtering

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Materials Sciences and Applications 2015年第4期6卷 263-268页

作者： kenta miura Takumi Osawa Yuya Yokota Tetsuhito Suzuki Osamu Hanaizumi Graduate School of Science and Technology Gunma University Kiryu Japan

We prepared thulium and cerium co-doped tantalum-oxide (Ta2O5 :Tm, Ce) thin films by radiofrequency co-sputtering of Tm2O3 and CeO2 pellets on a Ta2O5 disc for the first time, and photoluminescence (PL) properties of the films annealed at 700°C, 800°C, 900°C, or 1000°C for 20 min were evaluated. PL peaks around a wavelength of 800 nm due to Tm3+?were observed for films annealed at 900°C or 1000°C. The peak intensities of films prepared using one Tm2O3 pellet and one CeO2 pellet were much stronger than those of films prepared using one Tm2O3 pellet and two CeO2 pellets or films prepared using two Tm2O3 pellets and one CeO2 pellet. To obtain the strongest PL intensity from the film, the proper Tm concentration was estimated to be around 1.0 mol%, and the proper Ce concentration was estimated to be around 1.3 mol%. Such Ta2O5:Tm, Ce co-sputtered thin films can be used as high-refractive-index materials of autocloned photonic crystals that can be applied to novel light-emitting devices, and they will also be used as anti-reflection and downconversion layers for realizing high-efficiency silicon solar cells.

关键词： Tantalum Oxide Thulium Cerium Co-Sputtering Photoluminescence

Preparation of CuO-Ta2O5Composites Using a Simple Co-Sputtering Method

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Journal of Materials Science and Chemical Engineering 2015年第9期3卷 47-51页

作者： kenta miura Takumi Osawa Yuya Yokota Zobaer Hossain Osamu Hanaizumi Graduate School of Science and Technology Gunma University Kiryu Japan

We prepared CuO-Ta2O5 composite films using our simple co-sputtering method for the first time. Four specimens were prepared from an as-deposited CuO-Ta2O5 sample by cutting it using a diamond- wire saw, and the specimens were subsequently annealed at 600°C - 900°C. The X-ray diffraction and photoluminescence (PL) of the annealed specimens were evaluated. The CuO-Ta2O5 film annealed at 600°C seemed to be primarily amorphous phase, and a sharp PL peak at a wavelength of 450 nm, due to the existence of Cu2+, was observed from the film. In contrast, the CuO-Ta2O5 films annealed at 700°C, 800°C, and 900°C seemed to be tetragonal CuTa2O6 phases. We expect that good-quality CuTa2O6 films can be obtained using our very simple co-sputtering method and subsequent annealing above 900°C. Such CuTa2O6 films can be used in chemisorptions conductometric gas sensors.

关键词： Ta2O5 CuO Co-Sputtering X-Ray Diffraction Photoluminescence

Photoluminescence and X-Ray Diffraction Properties of Europium and Silver Co-Doped Tantalum-Oxide Thin Films Deposited by Co-Sputtering

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Journal of Materials Science and Chemical Engineering 2017年第2期5卷 35-40页

作者： Keisuke Shimada kenta miura Ryosuke Fujii Masahiro Kanakubo Wataru Kada Osamu Hanaizumi Graduate School of Science and Technology Gunma University Kiryu Japan

We fabricated europium and silver co-doped tantalum-oxide (Ta2O5:Eu, Ag) thin films using a simple co-sputtering method for the first time, and we evaluated their photoluminescence (PL) and X-ray diffraction (XRD) properties. We found that the most remarkable PL peak at a wavelength of 615 nm due to Eu3+ can be enhanced by Ag doping, and the strongest PL peak can be obtained from a Ta2O5:Eu, Ag thin film after annealing at 1000℃. Based on XRD measurements, we found that Ag2Ta8O21 crystalline phases produced by Ag doping are very important and Eu3TaO7 phases should be avoided in order to enhance the objective PL peak from our Ta2O5:Eu, Ag thin films.

关键词： Tantalum Oxide Europium Silver Co-Sputtering Photoluminescence