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91.
Influence of annealing conditions on impurity species in arsenic-doped HgCdTe grown by molecular beam epitaxy 下载免费PDF全文
Based on our previous work,the influence of annealing conditions on impurity species in in-situ arsenic (As)-doped Hg 1 x Cd x Te (x ≈ 0.3) grown by molecular beam epitaxy has been systematically investigated by modulated photoluminescence spectra.The results show that (i) the doped-As acting as undesirable shallow/deep levels in as-grown can be optimized under proper annealing conditions and the physical mechanism of the disadvantage of high activation temperature,commonly assumed to be more favourable for As activation,has been discussed as compared with the reports in the As-implanted HgCdTe epilayers (x ≈ 0.39),(ii) the density of V Hg has an evident effect on the determination of bandgap (or composition) of epilayers and the excessive introduction of V Hg will lead to a short-wavelength shift of epilayers,and (iii) the V Hg prefers forming the V Hg-As Hg complex when the inactivated-As (As Hg or related) coexists in a certain density,which makes it difficult to annihilate V Hg in As-doped epilayers.As a result,the bandedge electronic structures of epilayers under different conditions have been drawn as a brief guideline for preparing extrinsic p-type epilayers or related devices. 相似文献
92.
Dongho Park Nak‐Kyoung Choi Sang‐Gu Lee Jungho Hwang 《Particle & Particle Systems Characterization》2009,26(4):179-186
For this study, a 4 stage electrical low pressure impactor was designed to measure the real‐time size distribution of diesel particulate matter (DPM). For the performance evaluation, sodium chloride (NaCl) particles and dioctyl sebacate (DOS) particles were used. After evaluating the collection efficiency of each stage of the impactor, the size distributions of test particles were estimated using electrical current data and their inversion algorithm, and this was found to agree with the results obtained by a scanning mobility particle sizer (SMPS). For measurement of DPM, a common‐rail direct injection (CRDI) diesel engine, for engine speeds of 1,200 rpm and 1,500 rpm at 2.7 kgf·m, was used. Therefore, it was found that the size distribution of the DPM could be easily obtained, with the currents measured by the impactor and the data inversion algorithm, in less than 5 seconds. Furthermore, the effective density of the DPM could be obtained using the calculated results and the SMPS data. 相似文献
93.
The spectrum change of a Gaussian pulse in the far field is studied with the Fresnel diffraction integral when it is incident on an aperture with Gaussian form transmittance. It is found that the side-lobes of the diffracted spectral intensity, which exist in a normal circular aperture with unit transmittance, can be eliminated completely under such a condition. Also, the red shift and blue shift of the spectral intensity maximum of the incident pulse are presented. 相似文献
94.
95.
The Knoevenagel condensation of Meldrum's acid with aromatic aldehydes proceeded efficiently in a reusable ionic liquid, ethylammonium nitrate, at room temperature in the absence of any catalyst with high yields. 相似文献
96.
The reaction of diaryliodonium salts with β-substituted-α,β-enones in the presence of a palladium catalyst affords Hβ-substituted products with excellent yields. 相似文献
97.
C. L. Kuo T. L. Tsai A. C. Chiang K. S. Chang-Liao J. H. Chao 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(1):465-473
The purpose of this study is to develop a neutron activation method to determine trace amounts of 129I in cement-solidified radwastes. The radwaste samples were alkaline fused using KOH and then 129I and iodine carrier were chemically separated by solvent extraction before and after neutron irradiation. Both stable iodine (127I) and 129I can be activated by neutrons through 127I (n, 2n) 126I and 129I (n, γ) 130I reactions; their activated radionuclides were counted together with a high-purity germanium detector. The chemical recovery yields ranged from 30 to 60 %, and it was found that more than 99.9 % of interfering radionuclides can be removed using solvent extraction after neutron irradiation. The minimum detectable amounts can be lowered to less than 1 mBq g?1, which is superior to low energy γ-ray spectrometry by a factor of >102, on average. The established technique can be applied to re-evaluation of 129I content in radwastes that can be re-classified to lower classes, and the cost for designing a final disposal facility can be significantly reduced. 相似文献
98.
In this paper we describe a class of stochastic biochemical systems exhibiting bistable behavior, in the sense that the invariant measure associated to the system is concentrated near two different classes of states of the system. We develop methods that allow us to describe the behavior of the invariant measure in some suitable asymptotic limits, as well as the switching times for the transitions between the states close to each of the states with high probability. Due to the discrete character of the problem, switching times cannot be computed using the classical Kramers’ formula, and alternative methods are required. 相似文献
99.
A homologous series of 4,4'-bis(omega-hydroxyalkoxy)-alpha-methylstilbenes, denoted HAMS-n, has been synthesized. Here n is the carbon atom length of the peripheral n-alkyl chain; in this work n = 2 to 8 and 11. The composition, microstructure, thermal properties, and mesomorphism of the homologues were determined using elemental analysis, 1H NMR, FTIR, DSC, wide angle X-ray diffraction, and polarizing optical microscopy with a heating stage. The influence of the length and the even/odd numbers of methylene units of the peripheral chains on the variants of mesomorphism and the stability of mesophases, as well as on their transition temperatures, are discussed. The homologues with n = 8 and 11 were enantiotropic monomorphic, CrG (or CrH). The odd homologues showed monotropic trimorphism on cooling, while the even homologues exhibited enantiotropic trimorphism. A pronounced even/odd effect on the melting temperatures was observed. 相似文献
100.
Qingpei Xiang Dongfeng Tian Fanhua Hao Chengsheng Chu Ge Ding Jun Zeng Fei Luo 《Journal of Radioanalytical and Nuclear Chemistry》2014,299(3):1439-1445
In recent years, the cerium-doped lanthanum bromide, LaBr3 (Ce = 5 %) detector is increasingly playing an important role in radiation measurements because of its higher energy resolution (~3 % at 662 keV), faster luminescence decay time (~35 ns) and higher detection efficiency compared to 7.65 cm × 7.65 cm NaI(Tl) detector. Intrinsic spectra between 1,800 and 3,000 keV derived from internal radioactivity within LaBr3(Ce) scintillators have been investigated in some literatures, and these results are confirmed by the experiments in this work. In this paper, a new method for LaBr3(Ce) detector energy calibration from 100 to 2,000 keV is proposed using the intrinsic spectra (self-calibration) instead of the standard gamma sources. Proof-of-concept experiment results show that self-calibration can guarantee energy accuracy of better than 0.815 % and can be applied outside the laboratory. The stability and applicability of this method are also investigated systematically. 相似文献