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971.
已探明塔里木盆地下古生界碳酸盐岩地层储量巨大。对塔里木盆地西北部柯坪-巴楚-阿图什一带的4块区域开展了系统的野外和重点观测工作,包括蓬莱坝剖面、柯坪水泥厂剖面、托普郎剖面等。本研究通过考察塔里木盆地奥陶系碳酸盐岩热液溶蚀及相关现象。从野外产状、伴生关系以及矿物岩石学特征角度解剖奥陶系地层中热液矿物组合的地质特征。研究表明,该区域存在富镁流体、富氟流体和富硫流体3种流体,分别来源于封存卤水、火成活动和TSR热液。不同性质流体蚀变具有相似的分带性。 相似文献
972.
本文将磁偏转三级象差的工作推广,使适用于电子束入射处就有磁场的情况,导出一个能在任意平面上求三级偏转象差的公式,并经过数学处理,使公式简洁、换算方便。最后运用这套象差系数就水平一列式电子枪(PI枪)经偏转后所产生的光栅图形进行了分析和探讨。 相似文献
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974.
975.
DING GuoJian GUO LiWei XING ZhiGang CHEN Yao XU PeiQiang JIA HaiQiang ZHOU JunMing & CHEN Hong Beijing National Laboratory of Condensed Matter Physics 《中国科学:物理学 力学 天文学(英文版)》2010,(1)
Al x Ga 1-x N/GaN high-electron-mobility transistor (HEMT) structures with Al composition ranging from x = 0.13 to 0.36 are grown on sapphire substrates by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). The effects of Al content on crystal quality, surface morphology, optical and electrical characteristics of the AlGaN/GaN heterostructures have been analyzed. Although high Al-content (36%) heterostructure exhibits a distinguished photoluminescence peak related to recombination between the two-dimensional electron gas and photoexcited holes (2DEG-h), its crystal quality and rough surface morphology are poor. 2DEG mobility increases with the Al content up to 26% and then it apparently decreases for high Al-content (36%) AlGaN/GaN heterostructure. The increase of sheet carrier density with the increase of Al content has been observed. A high mobility at room temperature of 2105 cm 2 /V s with a sheet carrier density of n s = 1.10 × 10 13 cm -2 , for a 26% Al-content AlGaN/GaN heterostructure has been obtained, which is approaching state-of-the-art for HEMT grown on SiC. Sheet resistance as low as 274 Ω/□ has also been achieved. 相似文献
976.
连续太赫兹激光透射扫描成像实验研究 总被引:1,自引:0,他引:1
太赫兹成像可用于安检、反恐和工业生产等领域,已成为研究热点。由于连续太赫兹激光源体积较小、操作简单,因此,近几年对连续太赫兹激光成像的研究越来越多。基于C02激光泵浦甲醇气体生成的118.83μm激光,采用室温单元探测器、二维位移平台、聚乙烯透镜、光阑和计算机等器件组成的扫描透射成像系统对物体进行了成像实验,比较分析了扫描步长分别为1mm和0.5mm的成像结果。实验结果表明,由于增加光阑,实际成像功率下降,但此套成像系统在激光输出功率约为20mW时,仍成像清晰,且步长为0.5mm的成像效果更好。 相似文献
977.
978.
Two types of Mei adiabatic invariants induced by perturbation of Mei symmetry for nonholonomic controllable mechanical systems are reported. Criterion and restriction equations determining Mei symmetry after being disturbed of the system are established. Form and existence condition of Mei adiabatic invariants are obtained. 相似文献
979.
We perform a first-principles calculation based on density functional theory to investigate the interface between single layer graphene and metal oxides. Our study reveals that the monolayer graphene becomes semiconducting by single crystal SiO2 and Al2O3 contact, with energy gaps to - 0.9 and - 1.8 eV, respectively. We find the gap originates from the breakage of π bond integrity, whose extent is related to the interface atom configuration. We believe that our results highlight a promising direction for the feasibility to apply large scale graphene layers as building blocks in future electronics devices. 相似文献
980.
Influence of O2 Flux on Compositions and Properties of ITO Films Deposited at Room Temperature by Direct-Current Pulse Magnetron Sputtering
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Indium tin oxide (ITO) films were deposited on glass substrates at room temperature by dc pulse magnetron sputtering. Varying 02 flux, ITO films with different properties are obtained. Both x-ray diffractometer and x-ray photoelectron spectrometer are used to study the change of crystalline structures and bonding structures of ITO films, respectively. Electrical properties are measured by four-point probe measurements. The results indicate that the chemical structures and compositions of ITO films strongly depend on the O2 flux. With increasing O2 flux, ITO films display better crystallization, which could decrease the resistivity of films. On the contrary, ITO films contain less O vacancies with increasing O2 flux, which could worsen the conductive properties of films. Without any heat treatment onto the samples, the resistivity of the ITO film could reach 6.0 × 10^-4 Ω·cm, with the optimal deposition parameter of 0.2 scem O2 flux. 相似文献