Interface and oxide trap states of SiO2/GaN metal–oxide–semiconductor capacitors and their effects on electrical properties evaluated by deep level transient spectroscopy

The relationship between the electrical properties and the carrier trap properties of the SiO2/GaN metal–oxide–semiconductor (MOS) capacitors was investigated using electrical measurements and deep level transient spectroscopy (DLTS). The capacitance–voltage (C–V) measurement showed that the frequency dispersion of the C–V curves became smaller after an 800 °C annealing in O2 ambient. DLTS revealed that before the annealing, the interface trap states, in a broad energy range above the midgap of GaN, were detected with the higher interface state density at around 0.3 and 0.9 eV below the conduction band minimum (Ec) of GaN. Moreover, the oxide trap states were formed at around 0.1 eV below the Ec of GaN, plausibly indicating a slow electron trap with a tunneling process. Although both trap states affect the electrical reliability and insulating property of the SiO2/GaN MOS capacitors, they were found to drastically decrease after the annealing, leading to the improvement of the electrical properties.Shingo Ogawa, Hidetoshi Mizobata, Takuma Kobayashi, Takayoshi Shimura, Heiji Watanabe; Interface and oxide trap states of SiO2/GaN metal–oxide–semiconductor capacitors and their effects on electrical properties evaluated by deep level transient spectroscopy. J. Appl. Phys. 7 September 2023; 134 (9): 095704. https://doi.org/10.1063/5.016589

Effect of anti-alpha-fetoprotein serum on growth and plating efficiency of alpha-fetoprotein-producing hepatoma cells in vitro

The effect of a specific rabbit antiserum to rat alpha-fetoprotein (AFP) was examined on the growth and the plating efficiency of AFP-producing rat hepatoma cells (AH70Btc Clone 10-5) in cultures. The addition of anti-AFP serum to the culture medium inhibited cell growth moderately and inhibited plating efficiency markedly, although no inhibitory effect of complexes of AFP and antibody to AFP was observed on cell growth. Anti-AFP globulin in the immune serum was demonstrated on the cell surface by fluorescent antibody technique. Several clones producing low levels of AFP were obtained by long-term treatment of the original Clone 10-5 cells with anti-AFP serum. These treated clones showed characteristics that differed from the untreated original clone 10-5 cells: The relative plating efficiency of the treated clones on agar plates containing 5% anti-AFP serum was higher than the original Clone 10-15 cells and the amount of AFP secreted by the treated clones was lower.</p

Input and output budgets of radiocesium concerning the forest floor in the mountain forest of Fukushima released from the TEPCO's Fukushima Dai-ichi nuclear power plant accident

AbstractEstimations of radiocesium input and output concerning the forest floor within a mountain forest region have been conducted in the north and central part of the Abukuma Mountains of Fukushima, northeast Japan, after a 2–3 year period following the TEPCO Fukushima Dai-ichi nuclear power plant accident. The radiocesium input and output associated with surface washoff, throughfall, stemflow, and litterfall processes at experimental plots installed on the forest floor of evergreen Japanese cedars and deciduous Konara oaks have been monitored. Despite the high output potential in the mountainous forest of Fukushima, the results at both monitoring locations show the radiocesium input to be 4–50 times higher than the output during the summer monsoon in Fukushima. These results indicate that the radiocesium tends to be preserved in the forest ecosystem due to extremely low output ratios (0.05%–0.19%). Thus, the associated fluxes throughout the circulation process are key issues for the projecting the environmental fate of the radiocesium levels, along with the subsequent reconstruction of life emphasized within the setting

Control on the density and optical properties of color centers at SiO2/SiC interfaces by oxidation and annealing

Color centers in solids can serve as single photon emitters (SPEs) those are important in many quantum applications. Silicon carbide (SiC) is a promising host for color centers because of its well-established crystal growth and device technologies. Although color centers with extremely high brightness were found at the silicon dioxide (SiO2)/SiC interface, controlling their density and optical properties remains a challenge. In this study, we demonstrate control over the color centers at the SiO2/SiC interface by designing the oxidation and annealing conditions. We report that post-oxidation CO2 annealing has the ability to reduce the color centers at the interface and form well-isolated SPEs with bright emission. We also discuss the correlation between the color centers and electrically active defects.Takato Nakanuma, Kosuke Tahara, Katsuhiro Kutsuki, Takayoshi Shimura, Heiji Watanabe, Takuma Kobayashi; Control on the density and optical properties of color centers at SiO2/SiC interfaces by oxidation and annealing. Appl. Phys. Lett. 4 September 2023; 123 (10): 102102. https://doi.org/10.1063/5.016674

A Novel Ex Vivo Bone Culture Model for Regulation of Collagen/Apatite Preferential Orientation by Mechanical Loading

The anisotropic microstructure of bone, composed of collagen fibers and biological apatite crystallites, is an important determinant of its mechanical properties. Recent studies have revealed that the preferential orientation of collagen/apatite composites is closely related to the direction and magnitude of in vivo principal stress. However, the mechanism of alteration in the collagen/apatite microstructure to adapt to the mechanical environment remains unclear. In this study, we established a novel ex vivo bone culture system using embryonic mouse femurs, which enabled artificial control of the mechanical environment. The mineralized femur length significantly increased following cultivation; uniaxial mechanical loading promoted chondrocyte hypertrophy in the growth plates of embryonic mouse femurs. Compressive mechanical loading using the ex vivo bone culture system induced a higher anisotropic microstructure than that observed in the unloaded femur. Osteocytes in the anisotropic bone microstructure were elongated and aligned along the long axis of the femur, which corresponded to the principal loading direction. The ex vivo uniaxial mechanical loading successfully induced the formation of an oriented collagen/apatite microstructure via osteocyte mechano-sensation in a manner quite similar to the in vivo environment.Watanabe R., Matsugaki A., Ishimoto T., et al. A Novel Ex Vivo Bone Culture Model for Regulation of Collagen/Apatite Preferential Orientation by Mechanical Loading. International Journal of Molecular Sciences, 23, 13, 7423. https://doi.org/10.3390/ijms23137423

Impaired alignment of bone matrix microstructure associated with disorganized osteoblast arrangement in malignant melanoma metastasis

Malignant melanoma favors spreading to bone, resulting in a weakened bone with a high fracture risk. Here, we revealed the disorganized alignment of apatite crystals in the bone matrix associated with the homing of cancer cells by developing an artificially controlled ex vivo melanoma bone metastasis model. The ex vivo metastasis model reflects the progressive melanoma cell activation in vivo, resulting in decreased bone mineral density and expression of MMP1-positive cells. Moreover, less organized intercellular connections were observed in the neighboring osteoblasts in metastasized bone, indicating the abnormal and randomized organization of bone matrix secreted by disconnected osteoblasts. Our study revealed that the deteriorated microstructure associated with disorganized osteoblast arrangement was a determinant of malignant melanoma-related bone dysfunction.Matsugaki A., Kimura Y., Watanabe R., et al. Impaired alignment of bone matrix microstructure associated with disorganized osteoblast arrangement in malignant melanoma metastasis. Biomolecules, 11, 2, 1. https://doi.org/10.3390/biom11020131