Effects of Ag on electrical properties of Ag/Ni/p-GaN ohmic contact

Properties of the Ag/Ni/p-GaN structure at different temperatures are studied by Auger electron spectroscopy, scanning electron microscopy and high resolution x-ray diffraction. The effect of Ag in ohmic contact on the crystalline quality is investigated and the optimized value of annealing temperature is reported. The lowest specific contact resistance of 2.5 x 10(-4) Omega cm(2) is obtained at annealing temperature of 550 degrees C.

Thermal annealing behaviour of Ni/Au on n-GaN Schottky contacts

The Schottky behaviour of Ni/Au contact on n-GaN was investigated under various annealing conditions by current-voltage (I-V) measurements. A non-linear fitting method was used to extract the contact parameters from the I-V characteristic curves. Experimental results indicate that high quality Schottky contact with a barrier height and ideality factor of 0.86 +/- 0.02 eV and 1.19 +/- 0.02 eV, respectively, can be obtained under 5 min annealing at 600degreesC in N-2 ambience.

GaP中N和N和Ni对束缚激子压力行为的研究

于G批量导入至Hzhangdi

Ni-Cr系光谱选择性吸收薄膜制备与表征

太阳能选择性吸收薄膜是中高温太阳能集热器的最关键部分，目前世界很多国家都在积极研究工艺简单、成本低廉、性能优良稳定的中高温光谱选择性吸收薄膜。本论文根据金属陶瓷型太阳能光谱选择性吸收表面和磁控溅射技术的原理，在国内外研究发展的基础上，针对目前国内平板型太阳能集热器的现有状况，结合太阳能热水器建筑一体化的发展趋势，开展了磁控溅射制备光谱选择性吸收薄膜的研究。本工作以直流反应磁控溅射方法作为制备手段，选择Ni-Cr合金作为靶材，以N2, 02两种气体为反应气体，反应溅射制备折射率变化的NiCr-NiCrO,N

Upgrading of liquid fuel from the vacuum pyrolysis of biomass over the Mo-Ni/gamma-Al2O3 catalysts

High amounts of acid compounds in bio-oil not only lead to the deleterious properties such as corrosiveness and high acidity, but also set up many obstacles to its wide applications. By hydrotreating the bio-oil under mild conditions, some carboxylic acid compounds could be converted to alcohols which would esterify with the unconverted acids in the bio-oil to produce esters. The properties of the bio-oil could be improved by this method. In the paper, the raw bio-oil was produced by vacuum pyrolysis of pine sawdust. The optimal production conditions were investigated. A series of nickel-based catalysts were prepared. Their catalytic activities were evaluated by upgrading of model compound (glacial acetic acid). Results showed that the reduced Mo-10Ni/gamma-Al2O3 catalyst had the highest activity with the acetic acid conversion of 33.2%. Upgrading of the raw bio-oil was investigated over reduced Mo-10Ni/gamma-Al2O3 catalyst. After the upgrading process, the pH value of the bio-oil increased from 2.16 to 2.84. The water content increased from 46.2 wt.% to 58.99 wt.%. The H element content in the bio-oil increased from 6.61 wt.% to 6.93 wt.%. The dynamic viscosity decreased a little. The results of GC-MS spectrometry analysis showed that the ester compounds in the upgraded bio-oil increased by 3 times. it is possible to improve the properties of bio-oil by hydrotreating and esterifying carboxyl group compounds in the bio-oil.

Ni-MH电池稀土AB_2型贮氢合金负极材料的研究

本文主要对稀土AB_2型贮氢合金用于Ni-MH电池负极材料的电化学性能进行了研究。结果表明，（一）通过优化合金组分，发现多相结构的 LaNi_(2-x)Al_x合金(0.15 ≤ x ≤ 0.25)显示突出的放电性能和长的循环寿命；（二）非化学计量比贮氢合金呈现更高的放电容量和满意的活化性能；（三）原材料的纯度对合金的电极性能影响甚微；（四）退火使合金的结构重整，但对合金电极的电化学性能不利；（五）长时间球磨可以促进活化，但导致电化学容量迅速衰减；短时间球磨大大增加放电容量和提高倍率放电性能；（六）合金电极高能辐照可以激活合金电极的表面活性，促进活化，有效的控制自放电；（七）随着在热碱液中浸泡时间的增加，合金电极的充放电性能得到明显的改善；（八）以镍粉为导电剂的合金电极比以铜粉为导电剂的合金电极有较好的综合电化学性能；（九）温度对合金的电极性能有很大影响。在30 ℃和40 ℃ 测试温度下所得的放电容量几乎相同，但在60 ℃和70 ℃放电容量开始减少。随着温度增加，电极的活化过程加速，高倍率放电能力略有所增加。合金电极呈现不理想的低温放电性能；（十）循环后合金电极的 XPS、XRD、ICP、SEM的图谱分析表明，LaNi_2基合金的腐蚀是造成容量衰减的主要原因，合金的本征衰退也可能是造成容量衰减的原因之一。

氟化Π－烯丙基镍的合成及性质-Ni(naph)_2-AlEt_3-BF·OEt_2丁二烯聚合体系活性中心的研究

本文研究了环烷酸镍一三乙基铝一三氧化硼已醚络合物三组分体系催化丁二烯聚合的活性中心模型化合物氧化Π－烯丙基镍的合成及性质。由双环辛二烯－1,5－镍与烯丙基氧反应合成的氟化Π－烯丙基镍还没有得到纯的产物，但通过核磁、顺磁、紫外光谱等仪器分析及络合物的化学反应和水解产物的生成证实了氟化Π－烯丙基镍的存在。并试图通过改善合成条件避免副反应的及通过重结晶、生成稳定化合物、升华、减压蒸镏等法纯制产物。但最终都没有完全达到目的。现合成中能得到的最高产率可达76％，固体产物的纯度为75％左右。纯化方法局限性是由于产物的性质引起的。实验中发现，氧化Π－烯丙基镍通常以二聚体形式存在，是一种无定形的橙红色固体，具有易氧化，易水解，能发生歧化反应。能与卤代烷发生偶连反应的化学性质，并具有溶解度低，热稳定性高，单聚体易挥发等物理性质。用它作为丁二烯聚合的催化剂，得到的聚合物的顺－1,4结构比氯代Π－烯丙基镍体系得到的高。符合卤代Π－烯丙基镍系列中阴离子电负性越高，聚合物顺－1,4含量就越高的规律。但由于它在聚合中表现的低活性，不稳定性，否认了它作为环烷酸镍一三乙基铝一三氧化硼乙醚络合物体系活性中心的可能。当在聚合体系的分别添加三氟化硼乙醚络合物和三乙基铝组分后，都能催化聚合，并各有特点。由此分别讨论了三氟化硼乙醚给合物和三乙基铝件作用。但是任一两组分的组合都不能得到预斯的聚合结果，因此它们也不会是Ni(naph)_2-AlEt_3-BF_3·OEt_2体系的活性中心。只有当氟化Π－烯丙基镍，三氧化硼乙醚络合物。三乙基铝三组分共同组成的催化剂才得到了与环烷酸镍一三氧化硼乙醚混合物一三乙基铝体系相似的聚合结果。说明在形成活性中心过程中三个组分的作用都是不可忽视的。本文讨论了这两个体系的区别和联系，推测二者具有相同的活性中心结构。通过实验证明了环烷酸镍一三乙基铝一三氟化硼乙醚络合物体系生成这种结构是可能的。同时对这种活性中心结构的合理性以及它对于二烯定向聚合机理进行了讨论。

Y在固体电极的电化学过程及Y_(mm)-Ni和Y_(mm)-Fe合金制备

本文对YCl_3-KCl.NaCl熔体中Y在固体M_0，Ni和Fe电极上的电化学过程及用氯化的熔休电解制备Y_(mm)-Ni和Y_(mm)-Fe合金进行了系统研究。对电解时电解槽内熔体温度分布进行了测定，得出了电解制备Y_(mm)-Ni合金时槽内熔体温度分布图。结果表明，从阴极表面到电解槽内表面的温度递降不是均匀的，阴极附近出现一个高温区。随着边缘电解质温度的升高，阴极表面温度基本上平行地上升。电极表面温度超出边缘电解质温度随电解时阴极电流密度和电流强度的增大而增加，在一定范围内有很好的线性关系；当使用高阴极电流密度时，可高达近百度。

Ni基电极淀积前后表面处理对p-GaN欧姆接触的影响

在p-GaN上蒸发Ni/Au电极前,采用王水、HCl、缓冲HF进行前表面处理,O_2气氛下退火后,比较各电极样品的I-V特性和表面形貌.结果显示无表面处理时接触电阻最小,且溶剂处理后残留的电解质会影响电极的电流特性和稳定性.用俄歇电子能谱(AES)测试不同元素随深度分布情况,发现高温退火过程中NiO的形成有自动清洁p-GaN表面的作用,因此对于Ni基电极前表面处理不是必需的.再将样品用10%草酸溶液处理,其I-V特性显示接触电阻率明显下降;X射线光电子能谱(XPS)测试显示草酸溶液处理后电极表面Ni含量显著减少,而Au元素信号峰增强,说明表面高阻P型NiO被有效除去,对改善接触性能具有实际意义.

NiO removal of Ni/Au Ohmic contact to p-GaN after annealing

The Ni/Au contact was treated with oxalic acid after annealing in O_2 ambient, and its I-V characteristic showed the property of contact has been obviously improved. An Auger electron spectroscopy (AES) depth pro-file of the contact as-annealed showed that the top layer was highly resistive NiO, while an X-ray photo-electron spectroscopy (XPS) of oxalic acid treated samples indicated that the NiO has been removed effectively. A scanning electron microscope (SEM) was used to observe the surface morphology of the contacts, and it was found that the lacunaris surface right after annealing became quite smooth with lots of small Au exposed areas after oxalic acid treatment. When the test probe or the subsequently deposited Ti/Au was directly in contact with these small Au areas, they worked as low resistive current paths and thus decrease the specific contact resistance.

Ni?莫来石界面反应的XPS研究

国家自然科学基金