Effects of Mg-doping temperature on the structural and electrical properties of nonpolar a-plane p-type GaN films

Nonpolar(11–20) a-plane p-type GaN films were successfully grown on r-plane sapphire substrate with the metal–organic chemical vapor deposition(MOCVD) system. The effects of Mg-doping temperature on the structural and electrical properties of nonpolar p-type GaN films were investigated in detail. It is found that all the surface morphology, crystalline quality, strains, and electrical properties of nonpolar a-plane p-type GaN films are interconnected, and are closely related to the Mg-doping temperature. This means that a proper performance of nonpolar p-type GaN can be expected by optimizing the Mg-doping temperature. In fact, a hole concentration of 1.3×10^(18)cm^(-3), a high Mg activation efficiency of 6.5%,an activation energy of 114 me V for Mg acceptor, and a low anisotropy of 8.3% in crystalline quality were achieved with a growth temperature of 990℃. This approach to optimizing the Mg-doping temperature of the nonpolar a-plane p-type GaN film provides an effective way to fabricate high-efficiency optoelectronic devices in the future.

Preparation of Phlogopite-based Geopolymer and Its Surface Nonpolar Modification

Phlogopite-based geopolymer was first prepared successfully under the activation of lye by compression molding at 50 MPa for 1 minute.The geopolymer was endowed with nonpolar surface via brushing modified liquid at room temperature.Swill-cooked dirty oil,whose main component was fatty acid,was used as nonpolar modifier.The raw materials and geopolymer samples were characterized by XRD,FT-IR and SEM.The compression strength of 7-day specimen run up to 36.8 MPa and its surface static water contact angle could reach 132°.The solubility of phlogopite powder directly affected the compressive strength of geopolymers and the evaluation index of mechanical strength of geopolymer based on the solubility of phlogopite powder was proposed.

Treatment of tunnel wash waters-experiments with organic sorbent materials.PartⅠ:Removal of polycyclic aromatic hydrocarbons and nonpolar oil

Tunnel wash waters characterize all waters that run off after washing procedures of tunnels are performed.These waters represent a wide spectrum of organic and inorganic pollutants,such as polycyclic aromatic hydrocarbons(PAHs)and toxic metals.Removal of such contaminants from water runoff was investigated using laboratory tests after washing procedure was performed on two road tunnels in eastern Norway(Hanekleiv and Bragernes).Due to diverse character of both,treatment media and treated wash waters, the wh...

Structural and optical investigation of nonpolar a-plane GaN grown by metal-organic chemical vapour deposition on r-plane sapphire by neutron irradiation

Nonpolar （1150） a-plane GaN films are grown by metal-organic chemical vapour deposition （MOCVD） on r-plane （1102） sapphire. The samples are irradiated with neutrons under a dose of 1× 1015 cm-2. The surface morphology, the crystal defects and the optical properties of the samples before and after irradiation are analysed using atomic force microscopy （AFM）, high resolution X-ray diffraction （HRXRD） and photoluminescence （PL）. The AFM result shows deteriorated sample surface after the irradiation. Careful fitting of the XRD rocking curve is carried out to obtain the Lorentzian weight fraction. Broadening due to Lorentzian type is more obvious in the as-grown sample compared with that of the irradiated sample, indicating that more point defects appear in the irradiated sample. The variations of line width and intensity of the PL band edge emission peak are consistent with the XRD results. The activation energy decreases from 82.5 meV to 29.9 meV after irradiation by neutron.

Stress and morphology of a nonpolar a-plane GaN layer on r-plane sapphire substrate

The anisotropic strain of a nonpolar （1120） a-plane GaN epilayer on an r-plane （1102） sapphire substrate, grown by low-pressure metal-organic vapour deposition is investigated by Raman spectroscopy. The room-temperature Raman scattering spectra of nonpolar a-plane GaN are measured in surface and edge backscattering geometries. The lattice is contracted in both the c- and the m-axis directions, and the stress in the m-axis direction is larger than that in the c-axis direction. On the surface of this sample, a number of cracks appear only along the m-axis, which is confirmed by the scanning electron micrograph. Atomic force microscopy images reveal a significant decrease in the root-mean-square roughness and the density of submicron pits after the stress relief.

Luminescence of a GaN grain with a nonpolar and semipolar plane in relation to microstructural characterization

We report on the growth of the high-quality GaN grain on a r-plane sapphire substrate by using a self-organized SiN interlayer as a selective growth mask. Transmission electron microscopy, scanning electron microscopy, and Raman spectroscopy are used to reveal the effect of SiN on the overgrown a-plane GaN growth. The SiN layer effectively terminates the propagation of the threading dislocation and basal plane stacking faults during a-plane GaN regrowth through the interlayer, resulting in the window region shrinking from a rectangle to a ＂black hole＂. Furthermore, strong yellow luminescence （YL） in the nonpolar plane and very weak YL in the semipolar plane on the GaN grain is revealed by cathodoluminescence, suggesting that C-involved defects are responsible for the YL.

Groove-type channel enhancement-mode Al GaN/GaN MIS HEMT with combined polar and nonpolar AlGaN/GaN heterostructures

A novel groove-type channel enhancement-mode AlGaN/GaN MIS high electron mobility transistor（GTCE-HEMT）with a combined polar and nonpolar AlGaN/GaN heterostucture is presented. The device simulation shows a threshold voltage of 1.24 V, peak transconductance of 182 m S/mm, and subthreshold slope of 85 m V/dec, which are obtained by adjusting the device parameters. Interestingly, it is possible to control the threshold voltage accurately without precisely controlling the etching depth in fabrication by adopting this structure. Besides, the breakdown voltage（VB） is significantly increased by 78% in comparison with the value of the conventional MIS-HEMT. Moreover, the fabrication process of the novel device is entirely compatible with that of the conventional depletion-mode（D-mode） polar AlGaN/GaN HEMT. It presents a promising way to realize the switch application and the E/D-mode logic circuits.

Nonpolar a-plane light-emitting diode with an in-situ SiN_x interlayer on r-plane sapphire grown by metal-organic chemical vapour deposition

We report on the growth and fabrication of nonpolar a-plane light emitting diodes with an in-situ SiNx interlayer grown between the undoped a-plane GaN buffer and Si-doped GaN layer. X-ray diffraction shows that the crystalline quality of the GaN buffer layer is greatly improved with the introduction of the SiNx interlayer. The electrical properties are also improved. For example, electron mobility and sheet resistance are reduced from high resistance to 31.6 cm2/（V· s） and 460 Ω/respectively. Owing to the significant effect of the SiNx interlayer, a-plane LEDs are realized. Electrolurninescence of a nonpolar a-plane light-emitting diode with a wavelength of 488nm is demonstrated. The emission peak remains constant when the injection current increases to over 20 mA.

Analysis of Nonpolar Components from Ginseng of Different Ages

Nonpolar components from ginseng of different ages were extracted and analysed using a GC-MS technique to determine their chemical compositions. In total, 23 ingredients, mostly aliphatic compounds, were identified. The compounds extracted included 10,12-octadecadiynoic acid (12.81% - 36.43%), falcarinol (4.95% - 36.79%), n-hexadecanoic acid (0.60% - 9.70%), 9,12-octadecadienoic acid, ethyl ester (0.33% - 5.63%), 5,7-dodecadiyn-1,12-diol (0.97% - 3.85%), (Z)-9-octadecenamide (2.66% - 5.38%) and (Z,Z)-9,12-octadecadienoic acid (0.46% - 5.27%). The two major diyne compositions, falcarinol (8) and 10,12-octadecadiynoic acid (12), were the predominant components (over 50%) of the nonpolar extract of older ginseng. Moreover, the 10,12-octadecadiynoic acid obviously accumulated as the ginseng grew. Sitosterol, a universal metabolite in higher plants, makes up 55.80% of the content of 6-year-old ginseng, but markedly decreases in older ginseng. There was not much difference between the extracts of 8, 10, 12 and 16-year ginsengs, but the extracts of 6-year-old ginseng were distinctive.

基于N-P关联式计算溶剂化吉布斯自由能

溶剂化吉布斯自由能(ΔG_(solv))是一个重要的热力学参数,广泛用于化学、生物、药理等领域.尽管计算溶剂化吉布斯能的模型众多,但仍缺乏简易高效的预测模型.本文提出一种基于Arrhenius方程的N-P关联式计算方法,其中参数N、P分别描述溶剂-溶质体系的非极性效应及极性效应对溶剂化吉布斯能的贡献.当溶剂及溶质分子被赋予经验参数N、P值时,基于N-P关联式能对任何溶剂-溶质对的溶剂化吉布斯能进行计算.将6 238个溶剂化吉布斯能数据对N-P关联式进行了测试,均方根误差仅为0.698 kcal/mol,低于测试精度1 kcal/mol,证实了本文提出的N-P关联式能快速计算溶剂化吉布斯自由能.

极性、半极性和非极性InN薄膜的MOCVD外延生长与表征

利用金属有机化合物化学气相沉积(MOCVD)技术,在不同晶面的蓝宝石(Al2O3)衬底上实现了极性(0002)面、半极性(11-22)面和非极性(11-20)面InN薄膜的外延生长,并通过多种表征手段对三个不同极性面InN薄膜的结构和光学特性进行了系统研究。X射线衍射(XRD)曲线展示了(0002)、(11-22)和(11-20)面InN较强的衍射峰,表明InN薄膜具有较高的成膜质量。通过扫描电子显微镜(SEM)表面图发现,极性(0002)面InN的表面形貌较光滑,而半极性和非极性InN表面均存在未完全合并的孔洞。光致发光(PL)光谱展示,不同极性面InN的峰值能量在0.63 eV附近,并从极性、半极性到非极性逐渐红移。此外,可见-红外分光光度计测得的透射谱显示,极性(0002)面InN的吸收边约为0.85 eV,而半极性(11-22)面和非极性(11-20)面InN的吸收边约为0.78 eV,表明极性InN具有更大的斯托克斯位移。

High-Temperature Synthesis in Nonpolar Solvent for CsPbBr3 and CH3NH_3PbBr3 Perovskite Nanocrystals with High-Efficient Luminescence

We report a method to synthesize both organicinorganic CH3NH3PbBr3 and all-inorganic CsPbBr3 perovskite nanocrystals in nonpolar solvent at high temperature. The cesium oleate and CH3NH3Br （MABr） are prepared and then injected into the nonpolar solvent of octadecene including oleic acid, oleylamine, and lead halide. In the synthesis of organic-inorganic perovskites of CHaNH3PbBr3, the frequently-used polar solvent of dimetbylformamide or other polar solvents are not used. The prepared CsPbBr3 nanocrystals are spherical nanoparticles with the diameter of 250 nm. The CHaNH3PbBr3 perovskites are micro-scale hexagonal nanoplatelets. The colloidal perovskites exhibit high-efficient fluorescence and excellent stability.

Nonpolar Al_(x)Ga_(1−x)N/Al_(y)Ga_(1−y)N multiple quantum wells on GaN nanowire for UV emission

Nonpolar m-plane AlGaN offers the advantage of polarization-free multiple quantum wells(MQWs)for ultraviolet(UV)emission and can be achieved on the sidewalls of selective area grown GaN nanowires.We reveal that the growth of AlGaN on GaN nanowires by metal organic chemical vapor deposition(MOCVD)is driven by vapor-phase diffusion,and consequently puts a limit on the pitch of nanowire array due to shadowing effect.An insight into the difficulty of achieving metal-polar AlGaN nanowire by selective area growth(SAG)in MOCVD is also provided and can be attributed to the strong tendency to form pyramidal structure due to a very small growth rate of{1011}semipolar planes compared to(0001)c-plane.The nonpolar m-plane sidewalls of GaN nanowires obtained via SAG provides an excellent platform for growth of nonpolar AlGaN MQWs.UV emission from mplane Al_(x)Ga_(1−x)N/Al_(y)Ga_(1−y)N MQWs grown on sidewalls of dislocation-free GaN nanowire is demonstrated in the wavelength range of 318–343 nm.

Twofold bioinspiration of TiO_(2)-PDA hybrid fabrics with desirable robustness and remarkable polar/nonpolar liquid separation performance

The fundamental relationship between microstructure,constituent,processing and performances of separating materials is really a vital issue.Traditional preparation methods for separation membranes are complex,time-consuming and easy to be fouled.Also,the durability of conventional coatings on membrane is poor.By combination of bioinspiration from mussel adhesive and fish scales’underwater superoleophobicity,we propose a general route to prepare organic-inorganic hybrid coatings,while no complex apparatus is needed.Specifically,based on the biomimetic adhesion of polydopamine(PDA),we used it as a binder to adhere TiO_(2)nanoparticles and built rough microstructure on fabric.In this way,we obtained TiO_(2)-PDA treated fabric with special wettability.These TiO_(2)-PDA treated samples owned superamphiphilicity in air,underwater superoleophobicity(underwater oil contact angles(OCAs)>150°),underoil superhydrophobicity(underoil water contact angles(WCAs)>150°),excellent multiresistance;and can separate polar/nonpolar liquid mixture effectively.It also owned superaerophobicity underwater(underwater bubble contact angles(BCAs)>150°).The proposed TiO_(2)-PDA coatings are highly expected to be employed for real situation of water pollution remediation,self-cleaning,oil extraction and harsh chemical engineering issues.

780 nm波段高分光比消偏振分光片的制备及测试

消偏振分光片是空间光学中的重要分光元件,为了实现780 nm波段激光在大分光比条件下的稳定分光输出,设计并制备了一种高分光比消偏振分光片。使用TFCalc软件仿真设计了双面消偏振分光膜系,通过离子束辅助电子束热蒸镀技术制备了消偏振分光片样品。然后,使用透射电子显微镜、分光光度计对所制备样品进行了测量表征,得到了分光片的实际薄膜结构及透射光谱,光谱结果显示该分光片的透射率接近98%,s偏振光与p偏振光的透射率偏差小于0.3%。最后,搭建测试光路对分光片进行变偏振方向、变波长及长时间稳定性等测试。实验结果表明:该分光片在目标波段内的透射率接近98%,偏振方向大范围变化时透射率偏差小于0.2%,波长在772~792 nm内变化时透射率波动小于0.12%;10 h长时结果显示,当平均时间为100 s时,分光比与透射率的Allan方差分别为1.41×10-3和4.12×10-5。所提出的消偏振分光片具有良好的消偏振性能,可直接应用于光学测试计量和量子传感探测等精密测量领域。

Micro-LED器件:从极性c面到非极性或半极性的发展趋势

氮化镓作为第三代照明器件材料相较于第一代硅与第二代砷化镓在性能上有了很大提高,基于氮化镓的MicroLED器件也愈发被人们所关注。然而由于在传统c面上生长的LED其自身所固有的一些缺陷往往在实际应用中发射效率不高,如存在量子限制斯塔克效应、绿色间隙、载流子传输等问题。基于非极性或半极性的LED没有极化电场,具有较强的内量子效率,电子和空穴复合机率大等优点,对非极性和半极性Micro-LED器件的研究与应用引起了人们很大的兴趣。本文对非极性和半极性Micro-LED器件研究现状进行综述。首先从量子限制斯托克效应、绿色间隙、载流子传输、效率下降4个方面介绍了非极性和半极性氮化镓基材料的优势。接着针对缺陷位错、增加光提取效率与在不同电流密度下实现全彩显示等问题,介绍了芯片成形、图案刻蚀与阵列这3种技术,最后对Micro-LED作为下一代显示引领者进行了展望。希望对Micro-LED今后的研究有所帮助。

FT-SERS研究非极性R侧链氨基酸在银胶体系中的吸附状态

利用傅里叶变换表面增强拉曼光谱（FT-SERS）研究了以L-蛋氨酸为代表的非极性R侧链氨基酸在纳米银衬底上的吸附状态和相互作用的特性，并结合浓度、pH值的变化探讨了吸附作用的特点和规律。实验结果表明，L-蛋氨酸在银胶上的最佳FT-SERS的浓度范围为10^-3～10^-4mol·L^-1；其pH范围以酸性、等电点、碱性而分段，当pH值在等电点附近及酸碱度过大时的FT-SERS都较差；L-蛋氨酸与纳米银的作用是通过氨基、羧基、硫与银的物理、化学吸附，其吸附态随着pH值的变化而改变。结合文献，对非极性R侧链氨基酸与纳米银的吸附特性作了总结，以期有助于对氨基酸、蛋白质、多肽、酶等相关领域更深入的研究。

非极性硫化橡胶微波脱硫的研究

从微波能在非极性硫化橡胶中的转换规律着手，考察了不同的胶种、补强剂和废硫化胶粒径与脱硫时间以及温度的相关性，探讨了这些因素对脱硫胶物理性能和溶胀特性的影响。结果表明，粒径大的硫化胶物料温升速度快；ＮＲ硫化胶的温升速度比ＳＢＲ硫化胶快；炭黑补强硫化胶的温升速度比白炭黑补强硫化胶快。溶胀特性数据表明，ＮＲ的脱硫效果优于ＳＢＲ，硫化胶粒（粒径１～３ｍｍ）的脱硫效果优于硫化胶粉（４０目和６０目）；

表面活性剂加强氧化铝种分分解粒度分布研究

铝酸钠溶液中加入有机表面活性剂可以强化分解过程 ,增加产品氢氧化铝的粒度。其中加入硬脂酸是吸附在颗粒表面 ,使种子表面疏水 ;而石蜡油的加入可强化疏水性质 ,并在 2个或多个固体颗粒粘结时起着“桥梁”作用。对产品氢氧化铝用热重和红外光谱分析 ,得出产品氢氧化铝在低于 10 0 0℃焙烧后 ,有机物添加剂可有效分解 ,不会带入后面的铝电解工序中。

硅藻土的研究现状及进展

硅藻土具有多孔性、密度小、比表面积大、吸附性好、耐酸、耐碱、绝缘等特性,并且中国硅藻土矿储量丰富,所以硅藻土作为一种新型的吸附材料近年来已被广泛应用于许多工业部门。本文在简单介绍硅藻土化学成分、表面特性等性质的基础上,综述了近年来国内外用聚苯胺、聚乙烯亚胺等聚合物对硅藻土进行改性的方法,同时针对不同的工业废水介绍了目前硅藻土的改性方法以及改性前后的硅藻土作为吸附材料对工业废水中的染料、重金属离子以及非极性芳香烃吸附的研究进展,并展望了硅藻土作为新型的吸附材料的发展趋势。