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191.
An influence of electronic states at an insulator/GaN interface on the behavior of excess holes in an ultraviolet-illuminated metal/ SiO2/n-GaN structure has been studied by numerical simulations for weak (gate bias of −0.1 V ) and strong (−1 V ) depletion, in a wide range of excitation light intensities (from 1010 to 1020 photons cm−2 s−1) and for various bulk carrier lifetimes (from 1 to 100 ns). It has been found that the interface states with densities of 1012 eV −1 cm−2 dramatically reduce the total (integrated in the whole GaN layer) density of photogenerated holes and thus degrade the sensitivity of the metal/insulator/GaN-based photodetector. 相似文献
192.
Local elastic and thermal behaviors of dielectric breakdown regions in multilayer ceramic capacitors 下载免费PDF全文
Local elastic and thermal behaviors of dielectric breakdown regions in BaTiO3 based multilayer ceramic capacitors were investigated by acoustic and thermal mode scanning probe microscopy. Nanoscale elastic microstructures closely related to the dielectric breakdown‐induced stress release was found to develop in the BaTiO3 ceramic grains adjacent to the dielectric breakdown region. Such nanostructures could be supposed to be the origin of the elementary structures for the failure of MLCC. The breakdown region exhibits very lower thermal conductivity due to the possible glass phase formation. Such new findings provide a new clue to further understand the breakdown mechanism of multilayer ceramic capacitors. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
193.
Shyuan Yang Brian R. Tull Nadia K. Pervez Limin Huang Eli S. Leland Daniel A. Steigart Stephen O'Brien Ioannis Kymissis 《Journal of Polymer Science.Polymer Physics》2013,51(1):35-38
Nanoparticle polymer composite capacitors have been examined for some time as a route to high performance, printable capacitors. One approach to creating these composites is to use a particle film together with vapor deposited polymers, which can yield high performance, but also forms a structurally asymmetric device. The performance of a nanoparticle (Ba, Sr)TiO3 (BST)/parylene‐C composite capacitor is compared to that of a nanoparticle BST capacitor without the polymer layer under both directions of bias. The composite device shows a five orders of magnitude improvement in the leakage current under positive bias of the bottom electrode relative to the pure‐particle device, and four orders of magnitude improvement when the top electrode is positively biased. The voltage tolerance of the device is also improved and asymmetric (44 V vs. 28 V in bottom and top positive bias, respectively). This study demonstrates the advantage of this class of composite device construction, but also shows that proper application of the device bias in this type of asymmetrical system can yield an additional benefit. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013 相似文献
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195.
Deposition of aluminum nitride thin film on Si(1 1 1) by KrF excimer laser and its characterizations
We present the deposition of aluminum nitride (AlN) thin film by KrF excimer laser sputtering and the study of the effects of substrate temperature and laser fluences. Deposition rate of AlN thin film at 0.3 Å/pulse has been achieved with laser fluence of 1500 mJ/cm2 and at substrate temperature of 250 K, and this shows the enhancement of the deposition rate at low substrate temperature. Surface morphology of the deposited films is characterized by atomic force microscopy (AFM). In addition, the electrical performance of the MIS devices with AlN thin films prepared in this experiment has been characterized. 相似文献
196.
电化学电容器(超级电容器)是一种兼具高能量密度和高功率密度的新型储能元件,它既具有传统电容器大电流快速充放电的特性,又具有蓄电池高储能密度的特性. 近几年,电化学电容器储能机理的研究和纳米结构电极复合材料的合成不断取得新突破,超级电容器的电化学性能得到了显著的提高. 为了更好地解析电化学电容器的工作特性,建立描述电容器内部浓度分布和电场的物理模型是一项非常重要的研究方法. 本文首先介绍电化学电容器理论基础,并论述近几年电化学电容器连续模型研究进展,最后阐述连续模型进一步发展的前景和挑战. 相似文献
197.
Electric double-layer capacitors (EDLCs) are an excellent electrochemical energy storage system (ESS) because of their superior power density, faster charge–discharge ability, and longer cycle life compared to those of other EES systems. Activated carbons (ACs) have been mainly used as the electrode materials for EDLCs because of their high specific surface area, superior chemical stability, and low cost. Petroleum pitch (PP) is a graphitizable carbon that is a promising precursor for ACs because of its high carbon content, which is obtained as an abundant by-product during the distillation of petroleum. However, the processibility of PP is poor because of its stable structure. In this study, pre-oxidized PP-derived AC (OPP-AC) was prepared to investigate the effects of pre-oxidation on the electrochemical behaviors of PP. The specific surface area and pore size distribution of OPP-AC were lower and narrower, respectively, compared to the textural properties of untreated PP-derived AC (PP-AC). On the other hand, the specific capacitance of OPP-AC was 25% higher than that of PP-AC. These results revealed that pre-oxidation of PP induces a highly developed micropore structure of ACs, resulting in improved electrochemical performance. 相似文献
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199.
Dr. Shuhong Wu Chao Li Prof. Ying Wang Dr. Yan Zhuang Yi Pan Prof. Na Wen Dr. Shuo Wang Prof. Zizhong Zhang Zhenxin Ding Prof. Rusheng Yuan Prof. Wenxin Dai Prof. Xianzhi Fu Prof. Jinlin Long 《Angewandte Chemie (International ed. in English)》2023,62(36):e202309026
The keto-switched photocatalysis of covalent organic frameworks (COFs) for efficient H2 evolution was reported for the first time by engineering, at a molecular level, the local structure and component of the skeletal building blocks. A series of imine-linked BT-COFs were synthesized by the Schiff-base reaction of 1, 3, 5-benzenetrialdehyde with diamines to demonstrate the structural reconstruction of enol to keto configurations by alkaline catalysis. The keto groups of the skeletal building blocks served as active injectors, where hot π-electrons were provided to Pt nanoparticles (NPs) across a polyvinylpyrrolidone (PVP) insulting layer. The characterization results, together with density functional theory calculations, indicated clearly that the formation of keto-injectors not only made the conduction band level more negative, but also led to an inhomogeneous charge distribution in the donor-acceptor molecular building blocks to form a strong intramolecular built-in electric field. As a result, visible-light photocatalysis of TP-COFs-1 with one keto group in the skeletal building blocks was successfully enabled and achieved an impressive H2 evolution rate as high as 0.96 mmol g−1 h−1. Also, the photocatalytic H2 evolution rates of the reconstructed BT-COFs-2 and -3 with two and three keto-injectors were significantly enhanced by alkaline post-treatment. 相似文献