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951.
Measurements of the positron lifetime and Doppler-broadened annihilation-radiation have been performed in electron-irradiated GaAs. The positron lifetime at the irradiation induced defects was 0.250 ns at 300 K. The defect clustering stage was found to occur at around 520–620 K, and the coarsening and annealing stage is believed to be above 620 K. Similar annealing stages were also observed in GaAs lightly doped with Si (0.2×1018 cm–3). Both the lifetime and the S-parameter in the irradiated GaAs were found to decrease with temperature from 300 K to 100 K, suggesting the coexistence of shallow traps in electron irradiated GaAs. 相似文献
952.
Copper(I) thiocyanate (CuSCN) is one of the most robust hole-transport materials for perovskite solar cells (PSCs). However, the power conversion efficiency of CuSCN-based PSCs is low due to difficulty in crystallization of CuSCN. In this study, we focused on humidity conditions during the aging process of CuSCN-based PSCs to improve their performance. PSCs aged in humid air, i. e., at a relative humidity of 70 %, exhibited better performance (efficiency; 10.6 %) than those aged in lower humidity (5.9 %) due to improved crystallinity of CuSCN layers. The results of the study provide insights into how to improve fabrication process of CuSCN-based PSCs for higher stability and efficiency. 相似文献
953.
The ring-opening reaction of 3-(trimethylstannyl)cyclobutene gave a mixture of the (Z)- and (E)-1,3-dienes, whereas that of 3-tert-butylcyclobutene exclusively afforded the (E)-1,3-diene due to the steric influences. The contrasting rotational behaviors suggest that there is some effect operating with the 3-stannylcyclobutene to stabilize the inward transition state, counteracting the steric influences. This contrasteric effect is ascribed to negative hyperconjugation. The stannyl group in the inward transition state accommodates electron density from the breaking sigma orbital of the cyclobutene into its low-lying tin-carbon sigma orbital. Theoretical studies supported this interpretation. 相似文献
954.
Yasushi Murakami Kazuhiko Tanaka Yusuke Takechi Saki Takahashi Yuuki Nakano Taki Matsumoto Wataru Sugimoto Yoshio Takasu 《Journal of Sol-Gel Science and Technology》2004,29(1):19-24
Microporous silica was synthesized by the salt catalytic sol-gel process with extremely low content of water to tetramethoxysilane. Silica particles were precipitated even when the extent of hydrolysis was very low, since ammonium carbonate as a salt catalyst made the polycondensation faster than an acid catalyst. Microporous silica with a high surface area (680 m2 g–1) was obtained by combustion of methoxy groups at 450°C. The methoxy groups can be removed by the post-hydrolysis before heating. A high specific surface area (>750 m2g–1) of microporous silica was obtained with pore diameter between 1.2 and 2.0 nm. 相似文献
955.
Katsumata Hideyuki Kawanishi Tomoko Furukawa Mai Tateishi Ikki Kaneco Satoshi 《Journal of Analytical Chemistry》2022,77(5):581-587
Journal of Analytical Chemistry - A sensitive and selective mixed hemimicelles solid phase extraction magnetic material based on sodium dodecyl sulfate-coated magnetite (Fe3O4)/alumina (Al2O3) is... 相似文献
956.
Hikari Takahara Hiroyuki Murakami Toru Kinashi Chris Sparks 《Spectrochimica Acta Part B: Atomic Spectroscopy》2008
Hafnium silicate is a so-called high-k material, which is a new key material in the semiconductor field. This material is difficult to analyze by a conventional W-Lβ1TXRF source due to the high background originating from Hf-Lα lines. In this paper, the capability of Ir source TXRF analysis on hafnium silicate films is investigated with intentional contamination of Ti, Cr, Fe, Ni and Cu elements. The spectral fitting is discussed where X-ray resonant Raman scattering and escape peak of Ir-Lα overlap with Ni-Kα peak. The detection limits are estimated to 0.9 × 1010 to 2 × 1010 atoms/cm2 for the transition metals. 相似文献
957.
Hideyuki Ishi 《manuscripta mathematica》2009,130(3):353-358
We show that the isotropy group of a bounded homogeneous domain always has a non-trivial torus subgroup, which gives an answer
to the problem posed by Hundemer. 相似文献
958.
959.
960.
Hideyuki Higashimura Kiyoshi Fujisawa Masaaki Kubota Shiro Kobayashi 《Journal of polymer science. Part A, Polymer chemistry》2005,43(9):1955-1962
“Radical‐controlled” oxidative polymerization of phenol (p‐1) by (1,4,7‐triisopropyl‐1,4,7‐triazacyclononane)copper(II) catalyst was performed and compared with that of 4‐phenoxyphenol (p‐2) in detail. Although the coupling selectivity for p‐1 seemed to be controlled by the catalyst, the C? C coupling, which was excluded completely for p‐2, occurred to some extent. The initial reaction rate of p‐1 was much smaller than that of p‐2, leading to the difference of polymerization behavior between p‐1 and p‐2. The rate‐determining step would be the coupling of controlled radicals species from the ESR measurement of the reaction mixture. The polymer resulting from p‐1 consisted mainly of phenylene oxide units, but had no crystallinity in contrast to the crystalline polymer from p‐2. However, the present polymer showed the highest thermal stability in the polymers obtained by oxidative polymerization of p‐1. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1955–1962, 2005 相似文献