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气相色谱法测定车间空气中2,4-二氯苯氧基乙酸丁酯 总被引:2,自引:0,他引:2
介绍了一种用气相色谱法测定车间空气中 2 ,4-二氯苯氧基乙酸丁酯质量浓度的方法。最低检出限为 5 0pg,测定范围为 5 0 μg/ m3~ 2 .5 mg/ m3。 相似文献
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Comparative study of adsorption characteristics of Cs on the GaN (0001) and GaN (0001) surfaces 下载免费PDF全文
The adsorption characteristics of Cs on GaN (0001) and GaN (0001) surfaces with a coverage from 1/4 to 1 monolayer have been investigated using the density functional theory with a plane-wave uttrasoft pseudopotential method based on first-principles calculations. The results show that the most stable position of the Cs adatom on the GaN (0001) surface is at the N-bridge site for 1/4 monolayer coverage. As the coverage of Cs atoms at the N-bridge site is increased, the adsorption energy reduces. As the Cs atoms achieve saturation, the adsorption is no longer stable when the coverage is 3/4 monolayer. The work function achieves its minimum value when the Cs adatom coverage is 2/4 monolayer, and then rises with Cs atomic coverage. The most stable position of Cs adatoms on the GaN (000i) surface is at H3 site for 1/4 monolayer coverage. As the Cs atomic coverage at H3 site is increased, the adsorption energy reduces, and the adsorption is still stable when the Cs adatom coverage is 1 monolayer. The work function reduces persistently, and does not rise with the increase of Cs coverage. 相似文献
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A 150-nm-thick GaN photocathode with an Mg doping concentration of 1.6× 1017cm-3 is activated by Cs/O in ultrahigh vacuum chamber, and quantum efficiency (QE) curve of negative electron affinity transmission-mode (t-mode) GaN photocathode is obtained. The maximum QE reaches 13.0% at 290 nm. According to the t-mode QE equation solved from the diffusion equation, the QE curve is fitted. From the fitting results, the electron escape probability is 0.32, the back-interface recombination velocity is 5× 104 cm·s-1, and the electron diffusion length is 116 nm. Based on these parameters, the influence of GaN thickness on t-mode QE is simulated. The simulation shows that the optimal thickness of GaN is 90 nm, which is better than the 150-nm GaN. 相似文献
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GaN 光电阴极的理论研究主要集中在量子产额、电子能量分布和表面模型三个方面.国内对 GaN 光电阴极的研究尚处于起步阶段,存在基础理论不太明确、关键制备工艺欠成熟的问题.重点探讨了 GaN 光电阴极在发射机理、材料生长、表面净化、激活工艺的优化、变掺杂结构设计和稳定性等方面的研究动向、存在的相关问题及应采取的措施.根据实验结果提出了制备GaN光电阴极的可行性工艺流程.
关键词:
GaN
光电阴极
发展 相似文献
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分析了基于创新、 创业、 创意( 三创)教育的光电信息科学与工程专业实践教学体系构建原则, 构建了
“ 三个三”的实践教学体系, 分析了体系中各环节的目标. 提出三创教育在实践教学体系中的具体实施路径 相似文献
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We employ plane-wave with ultrasoft pseudopotential method to calculate and compare the total density of states and partial density of states of bulk-phase GaN,Ga0.9375 N,and GaN0.9375 systems based on the first-principle density-functional theory(DFT).For Ga and N vacancies,the electronic structures of their neighbor and next-neighbor atoms change partially.The Ga0.9375 N system has n-type semiconductor conductive properties,whereas the GaN0.9375 system has p-type semiconductor conductive properties.By studying the optical properties,the influence of Ga and N vacancy defects on the optical properties of GaN has been shown as mainly in the low-energy area and very weak in high-energy area.The dielectric peak influenced by vacancy defects expands to the visible light area,which greatly increases the electronic transition in visible light area. 相似文献
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针对应用型人才培养目标,分别从教学方法、教学内容、教学手段和考核方法这4个方面对光学实验教学进行了探讨,提出实验与理论教师的兼职,课堂理论与具体实验仪器原理的结合,优化了实验教学内容,划分实验教学单元,把演示实验与操作实验相结合,建立不同方位的考核体系. 相似文献