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There has been much research and speculation recently on the nature of radiation induced defects in zirconium and its alloys, and in particular on the absence of voids at high fluences and temperatures in the range 0.3 to 0.5 T m (T m is the absolute melting temperature). Wolfenden and Farrell1 have reviewed the evidence and suggest that α-Zr has so far resisted void formation during neutron irradiation because of: (a) the absence of a dislocation (loop or tangle) structure and/or (b) a low insoluble gas (e.g. helium) content. 相似文献
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The thickness of the altered layer created by ion bombardment of the 6H–SiC single crystal was determined by means of Auger electron spectroscopy (AES) depth profiling in conjunction with factor analysis. After pre-bombardment of the surface by argon ions with energies 1, 2 and 4 keV until the steady state, the depth profiles of the induced altered layers were recorded by sputtering with low energy argon ions of 300 eV. Since the position and shape of the carbon Auger peak depend on the perfection of the crystalline structure, they were used for depth profile evaluation by factor analysis. In this way the depth profiles of the damaged surface region could be estimated in dependence on the ion energy. As a result, the thickness of the altered layer of SiC bombarded with 1, 2 and 4 keV Ar ions using an incident angle of 80° as well as the corresponding argon implantation profile could be measured. 相似文献
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Kohji Kamada Yoshio Katano Yuji Enokido Nariaki Ookubo Isao Yoshizawa 《辐射效应与固体损伤》2013,168(3):275-287
In previous papers, one of the authors (K. K.) has observed the anomalous melting of the surface layer of deuteron implanted Al, containing so-called "tunnel structures", on the electron bombardment in transmission electron microscope. In the present paper, we intended to observe the evidence of the d-d nuclear reaction, expecting neutron emission, associated with the melting phenomenon. However, the result was rather unexpected. The melting phenomenon was certainly observed under the same experimental conditions as before. But, in spite of the melting, neutron emission associated with the nuclear reaction was not observed. And, more unexpectedly, X-ray emission of energy less than roughly 400 v keV was observed when specimens with a bubble structure, which never showed melting, were bombarded with electron beams. Several conceivable mechanisms are discussed which, however, are all not convincing to explain the melting. The melting is attributed to some excess energy generation. The error estimation of the radiation measurements was undertaken. 相似文献
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P. Kavouras M. Katsikini N. Vouroutzis C. B. Lioutas E. C. Paloura J. Antonopoulos Th. Karakostas 《Journal of Crystal Growth》2001,230(3-4):454-458
We study the effect of N+ and O+ implantation on the microhardness and the microstructure of epitaxially grown GaN. The microhardness is measured using a Knoop diamond indenter while information on the effect of implantation on the surface morphology, microstructure and electronic structure is provided by atomic force microscopy, cross-section transmission electron microscopy and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. It is demonstrated that implantation increases the surface microhardness. A possible mechanism for the surface hardening effect is based on the formation of N interstitials that pin the dislocations and prohibit the plastic deformation. In addition to the hardening effect, the implantation induced N interstitials introduce a characteristic resonance in the NEXAFS spectra, at 1.4 eV below the absorption edge. 相似文献
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Jia Zhang Yue Yuan Minling Gao Zheng Han Chengyan Chu Yuguo Li Peter C. M. vanZijl Mingyao Ying Jeff W. M. Bulte Guanshu Liu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(29):9976-9980
While carbon dots (C‐dots) have been extensively investigated pertaining to their fluorescent, phosphorescent, electrochemiluminescent, optoelectronic, and catalytic features, their inherent chemical exchange saturation transfer magnetic resonance imaging (CEST MRI) properties are unknown. By virtue of their hydrophilicity and abundant exchangeable protons of hydroxyl, amine, and amide anchored on the surface, we report here that C‐dots can be adapted as effective diamagnetic CEST (diaCEST) MRI contrast agents. As a proof‐of‐concept demonstration, human glioma cells were labeled with liposomes with or without encapsulated C‐dots and implanted in mouse brain. In vivo CEST MRI was able to clearly differentiate labeled cells from non‐labeled cells. The present findings may encourage new applications of C‐dots for in vivo imaging in deep tissues, which is currently not possible using conventional fluorescent (near‐infrared) C‐dots. 相似文献
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离子注入层的X射线光电子能谱分析 总被引:6,自引:0,他引:6
采用金属蒸汽真空弧(MEVVA)离子源发出的强束流脉冲钨离子,对H13钢进行了离子注入表面改性研究,借助X射线光电子能谱(XPS)考察了注入表面层中钨,氧,铁的化学状态,研究发现,钨离子注入层中钨元素以替位钨和三氧化钨形式存在,铁元素以金属铁和三氧化二铁形式出现,而且各价态元素的原子比随深度而变化。 相似文献
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We propose an original method for the determination of the physical properties of nanometer sized helium bubbles using spectrum imaging in an energy-filtered transmission electron microscope. Helium bubbles synthesized by high fluence implantation and thermal annealing in silicon are investigated. The acquisition parameters are determined to optimize both signal/noise ratio and time. The limitations to the extent of observable areas on a typical sample are explained. The necessary data correction and helium K-edge position measurement procedures are detailed and the accuracy of the method is discussed. Finally helium density maps are obtained and discussed. 相似文献
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Electrical and optical activation studies of AlxGa1−xN (x = 0.11 and 0.21) implanted with silicon were made as a function of ion dose and anneal temperature. Silicon ions were implanted at 200 keV with doses ranging from 1 × 1014 to 1 × 1015 cm−2 at room temperature. The implanted samples were subsequently annealed from 1100 to 1300 °C for 20 min in a nitrogen environment. A maximum electrical activation efficiency of 91% was obtained for the Al0.11Ga0.89N implanted with the highest dose of 1 × 1015 cm−2 even after annealing at 1150 °C. 100% activation efficiencies were successfully obtained for the Al0.21Ga0.79N samples after annealing at 1300 °C for both doses of 5 × 1014 and 1 × 1015 cm−2. The mobility of the Si-implanted AlxGa1−xN increases with annealing temperature, and the highest mobilities are 109 and 98 cm2/V·s for Al0.11Ga0.89N and Al0.21Ga0.79N, respectively. The cathodoluminescence (CL) spectra for all the samples exhibited a sharp neutral-donor-bound exciton peak, and the CL intensity increases with annealing temperature, indicating successive improved implantation damage recovery as the annealing temperature is increased. These results provide the optimum annealing conditions for activation of implanted Si ions in AlxGa1−xN. 相似文献