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Powerful recombination centers resulting from reactions of hydrogen with carbon–oxygen defects in n‐type Czochralski‐grown silicon (Phys. Status Solidi RRL 8/2017) 下载免费PDF全文
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A method of simulating the CV profiles of multilayer isotype semiconductors is presented which utilises a novel, non-iterative approach to the solution of Poisson's equation. Computer run times are typically of the order of a few minutes using PASCAL on a HP series 200 desk-top computer. Interface charge, degeneracy and deep levels may be included and the effects of quantum confinement may be approximated in some circumstances. We show the effects of varying the interface parameters on the resulting profiles and illustrate the technique with a fit to a CV profile, taken from a five-layer heterostructure, which has enabled us to determine the charged states at each interface and relate these states to interfacial recombination. 相似文献
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A. T. Naveed M. Q. Huda K. F. Abd El-Rahman J. Hartung J. H. Evans-Freeman A. R. Peaker D. C. Houghton C. Jeynes W. P. Gillin 《Journal of luminescence》1998,80(1-4):381-386
Strained Si1−xGex/Si quantum wells have been doped with erbium by implantation. A comparison is made with strained Si1−xGex/Si quantum wells and relaxed Si1−xGex, with x between 10% and 25%, doped with erbium during MBE growth. The erbium concentration was between 1×1018 and 5×1018 cm−3 throughout the active regions. Transmission electron microscopy, X-ray diffraction, and photoluminescence studies indicate that good regrowth can been achieved after full amorphisation by implantation of the strained quantum wells. The erbium luminescence is more intense in the Si1−xGex/Si layers, but erbium-implanted samples containing Si1−xGex exhibit defect luminescence in the region of 0.9–1.0 eV. These defects are also present when Si1−xGex/Si quantum wells are implanted with an amorphising dose of silicon, and then regrown. They are attributed to small germanium-rich platelets, rather than to erbium-related defects. Electroluminescence is presented from a forward biased erbium-implanted Si0.87Ge0.13/Si structure at a drive current density of only 1.8 mA/cm2. 相似文献
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A series of poly(methyl methacrylate)s with molecular weights in the range 3.0 × 104–1.03 × 106 have been prepared by anionic polymerization and their limiting viscosity numbers determined in a variety of solvents. It was found that whereas the higher-molecular-weight polymers behaved normally, the lower-molecular-weight polymers showed anomalous behavior. First, the limiting viscosity numbers of the lower-molecular-weight polymers were much higher than expected, and, second, their number-average molecular weights as measured by gel permeation chromatography were considerably smaller than those determined by membrane osmometry. 相似文献
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In this study, methanol extracts (MEs) and essential oil (EO) of Angelica purpurascens (Avé-Lall.) Gill obtained from different parts (root, stem, leaf, and seed) were evaluated in terms of antioxidant activity, total phenolics, compositions of phenolic compound, and essential oil with the methods of 2,2-azino-bis(3ethylbenzo-thiazoline-6-sulfonic acid (ABTS•+), 2,2-diphenyl-1-picrylhydrazil (DPPH•) radical scavenging activities, and ferric reducing/antioxidant power (FRAP), the Folin–Ciocalteu, liquid chromatography−tandem mass spectrometry (LC−MS/MS), and gas chromatography-mass spectrometry (GC−MS), respectively. The root extract of A. purpurascens exhibited the highest ABTS•+, DPPH•, and FRAP activities (IC50: 0.05 ± 0.0001 mg/mL, IC50: 0.06 ± 0.002 mg/mL, 821.04 ± 15.96 µM TEAC (Trolox equivalent antioxidant capacity), respectively). Moreover, EO of A. purpurascens root displayed DPPH• scavenging activity (IC50: 2.95 ± 0.084 mg/mL). The root extract had the highest total phenolic content (438.75 ± 16.39 GAE (gallic acid equivalent), µg/mL)). Twenty compounds were identified by LC−MS/MS. The most abundant phenolics were ferulic acid (244.39 ± 15.64 μg/g extract), benzoic acid (138.18 ± 8.84 μg/g extract), oleuropein (78.04 ± 4.99 μg/g extract), and rutin (31.21 ± 2.00 μg/g extract) in seed, stem, root, and leaf extracts, respectively. According to the GC−MS analysis, the major components were determined as α-bisabolol (22.93%), cubebol (14.39%), α-pinene (11.63%), and α-limonene (9.41%) among 29 compounds. Consequently, the MEs and EO of A. purpurascens can be used as a natural antioxidant source. 相似文献
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AR Engel 《Contemporary Physics》2013,54(6):523-526
This article reviews some of the applications of physics to the solution of archaeological problems. The use of magnetic, resistivity and electromagnetic surveying techniques for the location of buried features is described. Various methods of age determination are outlined while the problems associated with radiocarbon dating of organic material and thermoluminescent dating of pottery are discussed in detail. The techniques, including petrological examination, chemical analysis and isotopic analysis, employed in the physical examination of archaeological artefacts are described. Examples of the application of these techniques in establishing the source of the raw materials used in pottery, metal and stone implements and in elucidating the techniques of manufacture of pottery and metal objects are also given. 相似文献