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排序方式: 共有348条查询结果,搜索用时 171 毫秒
181.
Vanesa Romero Isabel Costas-Mora Isela Lavilla Carlos Bendicho 《Spectrochimica Acta Part B: Atomic Spectroscopy》2011,66(2):156-162
In this work, different Pd-based substrates (i.e. Pd wire, Pd-coated stainless steel wire and Pd-coated SiO2) are tried for microextraction of Hg prior to its release into a modified quartz T-cell so as to develop a cost-effective, sensitive and easy-to-handle coupling between solid-phase microextraction (SPME) and atomic absorption spectrometry. The new design allows a direct sample injection from the SPME device into a quartz T-cell thus avoiding analyte dilution. Mercury amalgamation onto a Pd wire provided the best performance in respect to sensitivity and fiber lifetime, but Pd wires could not be implemented in the SPME device due to their poor mechanical characteristics. On the contrary, Pd-coated SiO2 fibers could be easily adapted to the typical sampling device used for SPME. Narrow time-dependent absorption signal profiles that could be integrated within 25 s were obtained. The detection limit was 90 pg mL−1 of Hg, and the repeatability expressed as relative standard deviation was 4.3%. 相似文献
182.
分别在Si(110)和Si(111)衬底上制备了In Ga N/Ga N多量子阱结构蓝光发光二极管(LED)器件.利用高分辨X射线衍射、原子力显微镜、室温拉曼光谱和变温光致发光谱对生长的LED结构进行了结构表征.结果表明,相对于Si(111)上生长LED样品,Si(110)上生长的LED结构晶体质量较好,样品中存在较小的张应力,具有较高的内量子效率.对制备的LED芯片进行光电特性分析测试表明,两种衬底上制备的LED芯片等效串联电阻相差不大,在大电流注入下内量子效率下降较小;但是,相比于Si(111)上制备LED芯片,Si(110)上LED芯片具有较小的开启电压和更优异的发光特性.对LED器件电致发光(EL)发光峰随驱动电流的变化研究发现,由于Si(110)衬底上LED结构中阱层和垒层存在较小的应力/应变而在器件中产生较弱的量子限制斯塔克效应,致使Si(110)上LED芯片EL发光峰随驱动电流的蓝移量更小. 相似文献
183.
Wu-Ji Sun Yong-Yan Zhao Jin Zhou Xue-Feng Cheng Prof. Jing-Hui He Prof. Jian-Mei Lu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(18):4808-4813
Recently, resistance random access memories (RRAMs) have been studied extensively, because the demand for information storage is increasing. However, it remains challenging to obtain a flexible device because the active materials involved need to be nontoxic, nonpolluting, distortion-tolerable, and biodegradable as well adhesive to diverse flexible substrates. In this paper, tannic acid (TA) and an iron ion (FeIII) coordination complex were employed as the active layer in a sandwich-like (Al/active layer/substrate) device to achieve memory performance. A nontoxic, biocompatible TA-FeIII coordination complex was synthesized by a one-step self-assembly solution method. The retention time of the TA-FeIII memory performance was up to 15 000 s, the yield up to 53 %. Furthermore, the TA-FeIII coordination complex can form a high-quality film and shows stable ternary memory behavior on various flexible substrates, such as polyethylene terephthalate (PET), polyimide (PI), printer paper, and leaf. The device can be degraded by immersing it in vinegar solution. Our work will broaden the application of organic coordination complexes in flexible memory devices with diverse substrates. 相似文献
184.
We introduce the double-Hamiltonian evolution technique approach toinvestigate the unconventional geometric quantum logical gate with dissipation under the model of many identical three-level atoms in a cavity, driven by a classical field. Our concrete calculation is made for the case of two atoms for the large-detuning interaction of the atoms with the cavity mode. The main advantage of our scheme is of eliminating the photon flutuation in the cavity mode during the gating. The corresponding analytical results will be helpful for experimental realization of speed geometric quantum logical gate in real cavities. 相似文献
185.
Undoped GaSb is p-type with the residual acceptor concentration of about 1e17 cm−3 due to the gallium vacancies and gallium in antimony site. Counter-doping of GaSb with low level of Te can reduce the net carrier concentration resulting in higher optical transparency in a broad IR spectral range. In this work, the carrier concentration, mobility and sheet resistance of n-type and p-type Te-doped GaSb substrates were measured using Hall method at 300 K and 77 K. The Hall carrier concentration data at 300 K were correlated with the absorption coefficients of GaSb in the IR spectral range. An empirical relationship between these values was established. Based on this correlation, we discuss application of FTIR spectroscopy for non-destructive optical screening of the substrates that allows construction of the carrier concentration distribution map across GaSb wafers. Investigations of the electronic properties of the low-doped p-type and n-type GaSb substrates upon cooling down to 77 K indicate the reduction of the hole carrier concentration background for both GaSb types. This is evident from the decrease in the Hall-measured carrier concentration for p-type GaSb. For n-type GaSb, an increase in the carrier concentration is observed due to the reduction of the hole carrier concentration background. 相似文献
186.
187.
柔性太阳电池具有重量轻、可卷对卷连续生产、可卷曲、不易破碎、便于携带和可穿戴等特点,可在多种领域为人们提供电力,具有非常广泛的应用前景。近年来,在基于刚性衬底的有机/无机杂化钙钛矿太阳电池(PSC)展示了出色的功率转换效率之后,柔性PSC研究也受到了人们的广泛关注。目前,柔性PSC的转换效率已经达到了18.1%。本文介绍了近年来柔性PSC领域的相关研究工作,综述了已应用于柔性PSC的柔性基底、透明电极和界面传输层等关键材料近来的发展,并探讨了这些材料应用于柔性PSC时的优势和面临的主要问题,最后对柔性PSC未来的发展进行了展望。 相似文献
188.
Shengshan Qin Yinxiang Li Qiang Zhang Congcong Le Jiangping Hu 《Frontiers of Physics》2018,13(3):137502
We investigate superconductivity that may exist in the doped BaCoSO, a multi-orbital Mott insulator with a strong antiferromagnetic ground state. The superconductivity is studied in both t-J type and Hubbard type multi-orbital models by mean field approach and random phase approximation (RPA) analysis. Even if there is no C4 rotational symmetry, it is found that the system still carries a d-wave like pairing symmetry state with gapless nodes and sign changed superconducting order parameters on Fermi surfaces. The results are largely doping insensitive. In this superconducting state, the three \({t_{{2_g}}}\) orbitals have very different superconducting form factors in momentum space. In particular, the intra-orbital pairing of the \({d_{{x^2} - {y^2}}}\) orbital has an s-wave like pairing form factor. The two methods also predict very different pairing strength on different parts of Fermi surfaces. These results suggest that BaCoSO and related materials can be a new ground to test and establish fundamental principles for unconventional high temperature superconductivity. 相似文献
189.
F. Sima N. Stefan I.N. Mihailescu L.E. Sima E. Palcevskis I. Zalite 《Applied Surface Science》2009,255(10):5312-5317
We studied the influence of porous Al2O3 substrates on Ce-stabilized ZrO2-doped hydroxyapatite thin films morphology pulsed laser deposited on their top. The porosities of substrates were monitored by changing sintering temperatures and measured with a high pressure Hg porosimeter.The depositions were conducted in 50 Pa water vapors by multipulse ablation of the targets with an UV KrF* (λ = 248 nm, τ ∼ 25 ns) excimer laser. The surface morphology of synthesized nanostructures was investigated by scanning electron microscopy and atomic force microcopy. Ca/P ratio within the range 1.67-1.70 was found for hydroxyapatite coatings by energy dispersive spectroscopy.The films were further seeded with mesenchymal stem cells for in vitro tests. The cells showed good attachment and spreading uniformly covering the entire surface of samples. The complexity of film morphology which is increasing with substrate porosity was shown to have a positive influence on cultivated cells density. 相似文献
190.
A. Guillén-Cervantes Z. Rivera-Álvarez I. Koudriavtsev 《Applied Surface Science》2009,255(9):4742-4746
GaAs (1 0 0) substrates prepared in a quartz chamber under a H2/As4 flux, and then exposed to air were used for the subsequent growth of GaAs-AlGaAs single quantum wells by molecular beam epitaxy. The substrates prepared by this method showed atomically flat surfaces corroborated by atomic force microscopy analysis. Quantum wells grown directly on these substrates without a GaAs buffer layer exhibited narrow and intense photoluminescence peaks, an indication of a high quality material. The secondary ion mass spectroscopy analysis showed oxygen and carbon traces on the first AlGaAs barrier layer grown after air exposure with no effects on the quantum wells optical emissions. From the results we conclude that the prepared GaAs surfaces are useful for the epitaxial growth of high quality quantum structures. 相似文献