北京边界层大气中HONO和NO2垂直廓线的测量与分析

基于扫描长程差分吸收光谱(DOAS)系统于2007年8月27日～9月4日期间对北京市郊区进行了大气污染物HONO和NO2等垂直廓线的连续监测,详细探讨了HONO,NO2和HONO/NO2比值的垂直分布特征,重点研究了HONO的形成途径.结果显示HONO和NO2浓度随着高度的增加而降低,而HONO浓度梯度下降的更加剧烈;...     

A novel 9-MC-3 and 15-MC-6 onset stacked metallacrown single-molecule magnet: synthesis and crystal structure

A novel enneanuclear manganese complex, [Mn(9)O(4)(Mesao)(6)(MeO)(3)(O(2)CMe)(3)(OH)(MeOH)(2)]·2.5DMF [1; Me-saoH(2) = 2-hydroxyphenylethanone oxime], was synthesized. The structure of 1 contains an unusual [Mn(9)O(4)] core with an unprecedented defective "supertetrahedron" topology based on two parallel, onset stacked 9-MC-3 and 15-MC-6 metallacrown subunits. Magnetic studies indicate that 1 behaves as a single-molecule magnet.     

GaN hexagonal pyramids formed by a photo-assisted chemical etching method

A series of experiments were conducted to systematically study the effects of etching conditions on GaN by a con-venient photo-assisted chemical （PAC） etching method. The solution concentration has an evident influence on the surface morphology of GaN and the optimal solution concentrations for GaN hexagonal pyramids have been identified. GaN with hexagonal pyramids have higher crystal quality and tensile strain relaxation compared with as-grown GaN. A detailed anal- ysis about evolution of the size, density and optical property of GaN hexagonal pyramids is described as a function of light intensity. The intensity of photoluminescence spectra of GaN etched with hexagonal pyramids significantly increases compared to that of as-grown GaN due to multiple scattering events, high quality GaN with pyramids and the Bragg effect.     

Synthesis and infrared and fluorescence spectra of new europium and terbium polynuclear complexes with an amide-based 1,10-phenanthroline derivative

An amide-based 1,10-phenanthroline (phen) derivative and its complexes with europium(III) and terbium(III) ions were synthesized. The complexes were characterized by elemental analysis, infrared spectra and conductivity. The europium and terbium ions were coordinated by O atoms of C=O, Ar-O-C and N atoms of phen. The fluorescence properties of the complexes in THF, dioxane, MeCN and DMF were investigated. Under the excitation of UV light, these complexes exhibited characteristic fluorescence of europium and terbium ions. The solvent factors influencing the fluorescent intensity were discussed.     

SBT-memristor-based crossbar memory circuit

Implementing memory using nonvolatile, low power, and nano-structure memristors has elicited widespread interest. In this paper, the SPICE model of Sr_0.95Ba_0.05TiO₃ (SBT)-memristor was established and the corresponding characteristic was analyzed. Based on an SBT-memristor, the process of writing, reading, and rewriting of the binary and multi-value memory circuit was analyzed. Moreover, we verified the SBT-memristor-based 4×4 crossbar binary and multi-value memory circuits through comprehensive simulations, and analyzed the sneak-path current and memory density. Finally, we apply the 8×8 crossbar multi-value memory circuits to the images memory.     

Approach to Single-Mode Dominated Resonant Emission in Ga N-Based Square Microdisks on Si

Square microdisks with round corners are fabricated using a standard GaN-based blue LED on Si substrates.Whispering gallery-like inodes in the square microdisks are investigated by finite-difference time-domain simulation.The simulation results reveal that the round corners in square microdisks can substantially suppress the number of light propagation paths and further reduce the number of optical modes.A con focal microphotoluminescence is performed to analyze the optical properties of the squ...     

Human fibrinogen adsorption onto single-walled carbon nanotube films

The adsorption behavior of human fibrinogen (Hfg) on single-walled carbon nanotube (SWNT) films was investigated using scanning electron microscopy (SEM) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. It was shown in the SEM images that fibrinogen was adsorbed strongly on the surface of SWNT when the samples were incubated in the Hfg solutions for 10 min. The dependence of adsorption on the concentration of fibrinogen was also investigated and it was found that adsorption increased with increasing concentration. In order to further explore the adsorption of fibrinogen on SWNT surface, NEXAFS spectra were obtained at the N K-edge and the C K-edge. The results confirmed the conclusion regarding the dependence of adsorption on fibrinogen concentration. It is demonstrated that, due to its high sensitivity to the surface elements, NEXAFS spectroscopy is a powerful tool to investigate the adsorption of fibrinogen on SWNT films.     

High-field-induced electron detrapping in An AlGaN/GaN high electron mobility transistor

A step stress test is carried out to study the reliability characteristics of an AlGaN/GaN high electron mobility transistor(HEMT).An anomalous critical drain-to-gate voltage with a negative temperature coefficient is observed in the stress sequence,beyond which the HEMT device starts to recover from degradation induced by early lower voltage stress.While the performance degradation featuring the drain current slump stems from electron trapping in the surface or bulk states during low-to-medium bias stress,the recovery is attributed to high field induced electron detrapping.The carrier detrapping mechanism could be helpful for lessening the trapping-related performance degradation of a GaN-based HEMT.     

GaN1-xPx薄膜的结构特性研究

用金属有机物化学气相沉积技术在蓝宝石衬底上外延了高P组分的GaN1-xPx 薄膜.利用x射线衍射仪和拉曼光谱仪研究了P对GaN1-xPx晶体结构的影响.研究结果表明:随着P组分比的增加,GaN1-xPx(0002)衍射峰逐渐向小角度移动,即晶格常数变大;与非掺杂GaN相比,GaN1-xPx薄膜的拉曼光谱中出现了4个新的振动模式,将它们分别归因于P族团引起的准局部振动模式、Ga-P键振动引起的间隙模,以及来自缺陷引起的无序激活散射.同时,随着P组分比的增加,A1(LO)模式的频率向低频方向移动,这种红移现象起因于合金化和应变的影响.     

GaN1-xPx薄膜的结构特性研究

用金属有机物化学气相沉积技术在蓝宝石衬底上外延了高P组分的GaN_1-xP _x 薄膜.利用x射线衍射仪和拉曼光谱仪研究了P对GaN_1-xP_x晶体结构 的影响.研究结果表明：随着P组分比的增加，GaN_1-xP_x（0002）衍射 峰逐渐向小角度移动，即晶格常数变大；与非掺杂GaN相比，GaN_1-xP_x薄 膜的拉曼光谱中出现了4个新的振动模 关键词： 1-xP_x')" href="#">GaN_1-xP_x 金属有机物化学气相沉积 x射线衍射 拉曼光谱