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101.
n-GaN肖特基势垒光敏器件的电子辐照效应 总被引:1,自引:1,他引:0
本文主要研究了n型GaN肖特基紫外光敏器件(包括GaN肖特基势垒紫外探测器,GaN肖特基二极管)的电子辐照效应和失效机理,以及辐照后二极管对不同波长光的光敏特性的变化。从实验中观测到,随着辐照注量的不断增加,GaN光敏器件的击穿电压明显减小,反向漏电流逐渐增大。证实了辐照后Au/GaN间产生的界面态是引起GaN肖特基势垒光敏器件辐照失效的原因。另外,在研究辐照效应对GaN肖特基二管光敏特性的影响时观测到,经过一定剂量的辐照后,GaN肖特基二管能探测到380nm的紫外光和可见光,而在辐照以前,它是探测不到的。这说明辐照效应将导致肖特基势垒光敏器件对较长波长的吸收,使得UV探测器中可见光成分的背景噪声增加。 相似文献
102.
In previous investigations the formation of radicals induced by γ-irradiation in CR-39 samples has been studied by electron spin resonance (ESR) spectroscopy. On the other hand, all attempts fail to detect radicals in samples irradiated by particles (p, and neutrons). The present work succeeded in detection of radicals produced by charged particle radiation in CR-39 (TASTRAK). The detectors were irradiated with protons of 7 MeV and -particles of 3 MeV with fluences in the order of 1011–1012 particles/cm2. The observed ESR signal is composed of at least four different resonance lines for each of which we determined the amplitudes, g-factors, lifetimes and the G-value. The amplitude of the total ESR signal decreases rapidly with a short and a longer lifetime. About 5 days after irradiation the ESR intensity decreased to an undetectable value. The lowest detectable dose (LDD) is of the order of 1 kGy. 相似文献
103.
Moura E. A. B. Lugo A. B. Andrade E Silva L. G. 《Radiation Physics and Chemistry》1998,52(1-6):229-232
TFE is highly unstable. It can easily go through an explosive disproportionation reaction under polymerization. The present work proposes the use of ionizing radiation for the study of monomer stability by inducing the polymerization and disproportionation reactions. Radiation was used to promote the initiation of TFE polymerization with and without inhibitors. Inhibitors and TFE were irradiated by γ-rays from 60Co. Small explosions with polymerization were observed yielding oligomer and polymer plus byproducts. It was shown that the initiation was completely inhibited by the addition of 0.1% of -pinene, dipentene, terpinolene or its mixture 1:1:1. In conclusion, radiation is a safe, reliable and easily controllable method to study TFE stabilization. 相似文献
104.
Application of microwave method to the solid phase synthesis of pseudopeptides containing ester bond
Bishnu Prasad Joshi 《Tetrahedron letters》2008,49(1):98-101
A new procedure was developed for reducing the reaction time and improving the yield of esterification reaction in solid phase synthesis of pseudopeptides containing an ester bond by utilizing microwave irradiation. We selected a pseudodipeptide (Fmoc-LysΨ[COO]Leu-NH2) and optimized the microwave-assisted esterification reaction in solid phase synthesis using Fmoc chemistry. For this, microwave-assisted esterification reactions with different reaction time, temperature, and solvents were performed using 1,3-diisopropylcarbodiimide (DIC) as the coupling reagent. We synthesized several pseudodipeptides containing an ester bond by using the optimized microwave irradiation method. The purity and yield of the pseudodipeptides synthesized in this way were better than those obtained without microwave irradiation. Furthermore, we applied this methodology for synthesizing pseudopeptides (6- and 12-mer) corresponding to the α helical peptide. The microwave-assisted esterification reaction afforded the target pseudopeptides with high yield (∼80%) and purity within 12 min, whereas the reaction without microwave irradiation afforded the target compound with poor yield (∼45%) and low purity. 相似文献
105.
L. Peruchon E. Puzenat A. Girard-Egrot L. Blum J.M. Herrmann C. Guillard 《Journal of photochemistry and photobiology. A, Chemistry》2008,197(2-3):170-176
The photocatalytic properties of commercialized self-cleaning glasses have been evaluated by the degradation of stearic acid C17H35COOH (SA), selected as a model molecule representative of fatty dirt. The relative amount of SA has been determined by measuring the FTIR peak area in the range 2752 and 2992 cm−1 corresponding to the C–H stretching bands. In order to estimate the thickness of one layer, the deposit of SA has been performed using the Langmuir–Blodgett (LB) method, which allows obtaining organized monomolecular layers of amphiphilic organics on a substrate. The thickness of one SA layer, obtained by Langmuir–Blodgett deposition, has been correlated to the FTIR signal. The photocatalytic degradation of a SA layer of a controlled thickness was carried out in a double jacket Pyrex reactor equipped with a UV Philips HPK 125 lamp. The photocatalytic degradation rate of the SA layer with different thicknesses was determined. The SA degradation rate was investigated under UV-A and UV-B irradiations to determine the influence of the photon wavelength range on efficiency. 相似文献
106.
Nakagawa K Ikota N Anzai K 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,69(5):1384-1387
We investigated the sucrose radical-production cross-section induced by heavy-ion irradiation. L-alanine was also used in order to compare radical yield and cross-section. The stable free radicals after irradiation were analyzed by electron paramagnetic resonance (EPR). The radical yield obtained by the irradiated samples had a logarithmic correlation with the LET (linear energy transfer). Quantitative EPR analyses showed that radical productions for sucrose and L-alanine vary both by different particle irradiation and the LET under the same absorbed dose. Furthermore, the cross-sections of radical productions for samples were calculated. Both cross-sections for C ions irradiation under LET 30 keV/microm at 50 Gy dose were approximately 3.0x10(-9) microm(2), taking account of the molecular areas of the samples. The values of the cross-sections imply that multiple ionizing particles involve producing stable radicals. 相似文献
107.
John R. Moss Siyabonga Ngubane Banothile C.E. Makhubela Jay A. Labinger Lawrence M. Henling 《Journal of organometallic chemistry》2008,693(16):2700-2702
Irradiation of Cp∗Ru(CO)2CH3 (1) in C6D6 at room temperature yields Cp∗Ru(CO)2C6D5 and CH3D (where Cp∗ = n5-C5Me5). Cp∗Ru(CO)2CD3 (2) has also been prepared and similar irradiation in C6H6 yields Cp∗Ru(CO)2C6H5 (3) and CD3H. This latter reaction confirms that it is the methyl group bonded to ruthenium that is involved in the C-H activation process and not the methyl groups on the Cp∗ ligand system. The compound Cp∗Ru(CO)2C6H5 (3) has been prepared for the first time in good yield by the reaction of Cp∗Ru(CO)2Br with NaBPh4. X-ray crystal structures of both Cp∗Ru(CO)2CH3 (1) and Cp∗Ru(CO)2C6H5 (3) have been determined and the results are reported and discussed. 相似文献
108.
The effect of ionizing radiation on the surface and electrokinetic characteristic parameters for a porous membrane of pore size 0.2 mum is determined and correlated with the irradiation dose (10 and 80 J/kg). Changes in NaCl permeability and membrane system electrical resistance determined from diffusion and impedance spectroscopy measurements are consistent with the increase of membrane pore radii/porosity, in agreement with SEM micrographs and reported results. Low irradiation dose seems to clean the membrane surface of impurities, according to XPS results, but the increase of irradiation doses could affect surface roughness. Due to the relatively high pore radius, ion transport numbers are practically independent of radiation and dose, but irradiation slightly modifies the membrane solution interface by increasing its weakly electronegative character, which could be of interest in the ultrafiltration of proteins or macromolecules. 相似文献
109.
We have used electron spin resonance spectroscopy to study the defects induced in yttria-stabilized zirconia (YSZ) single crystals by 2.5-MeV electron irradiations. Two paramagnetic centers are produced: the first one with an axial d 111 symmetry is similar to the trigonal Zr 3+ electron center (T center) found after X-ray irradiation or thermo-chemical reduction, whereas the second one is a new oxygen hole center with an axial d 100 symmetry different from the orthorhombic O m center induced by X-ray irradiation. At a fluence around 10 18 e/cm 2 , both centers are bleached out near 600 v K, like the corresponding X-ray induced defects. At a fluence around 10 19 e/cm 2 , defects are much more stable, since complete thermal bleaching occurs near 1000 v K. Accordingly, ageing of as-irradiated samples shows that high-dose defects at more stable than the low-dose ones. 相似文献
110.
S. P. Tripathy R. Mishra K. K. Dwivedi S. Ghosh D. Fink D. T. Khathing 《辐射效应与固体损伤》2013,168(8):583-591
Optical and thermal responses of two cellulose detectors, Cellulose triacetate (Triafol-TN) and Cellulose acetate butyrate (Triafol-BN), to four different doses of 62 MeV protons were studied using spectroscopic, thermal and track-etching techniques. The spectroscopic analysis revealed that though the optical band-gap in the polymers was affected by proton irradiation, the polymers showed high resistance against any major structural modification by radiation. The thermal stability of the polymers was found to be affected by proton irradiation. The activation energy of etching was found to be almost constant for both the polymers even after irradiation. It is hoped that the findings in this work would be of significant relevance to material science and applications of polymers. 相似文献