用光学方法研究玻璃微珠电流变液颗粒间的相互作用

运用一套适合研究颗粒间相互作用的双光镊系统,通过对粒聚集时间的测量,得出颗粒聚集时间和电场的平方成反比。这是第一次用电流变液颗粒在动态情况下直接验证电偶极子对间的相互作用。发展了一套使用高速CCD摄像机进行扩散波谱（DWS）测量的方法,首次实时测量具有颗粒结构的非各态历经体系的自相关函数,以研究电流变液机理,得到了玻璃微珠电流变液的结构响应时间和力和响应时间;测量了不同电场下体系相关函数的特征衰减时间随时间的变化。在不同电场下测量扩散系数可以反映出相互作用力与电场的平方成正比。     

Discrete Charge Storage Nonvolatile Memory Based on Si Nanocrystals with Nitridation Treatment

A nonvolatile memory device with nitrided Si nanocrystals embedded in a floating gate was fabricated. The uniform Si nanocrystals with high density （3× 10^11 cm^-2 ） were deposited on ultra-thin tunnel oxide layer （- 3 nm） and followed by a nitridation treatment in ammonia to form a thin silicon nitride layer on the surface of nanocrystals. A memory window of 2.4 V was obtained and it would be larger than 1.3 V after ten years from the extrapolated retention data. The results can be explained by the nitrogen passivation of the surface traps of Si nanoerystals, which slows the charge loss rate.     

新型光谱可调定标光源系统准直物镜设计

高精度光谱可调定标光源系统是针对高光谱遥感器的高精度定标提出的一种新型参考光源,设计了一个折射式宽谱段大相对孔径的准直物镜。镜头工作在400 nm~1 000 nm波段,半视场角2.2、相对孔径F/2.8、焦距135 mm。利用部分色散（P）和阿贝数（）的修正公式,基于复消像差的基本原理,获得了镜头的初始结构。借助Zemax光学设计软件进行优化设计,点校正了系统的二级光谱。最后,在设计波段上实现了复消色差,二级光谱残余量约为0.04 mm,其他像差也得到了良好的平衡。镜头的MTFs在37 lp/mm空间频率处均大于0.8,镜头整体性能满足设计指标。     

超薄氢化非晶锗膜的结构与光电性质

通过PECVD制备出了不同厚度的a-Ge∶H膜,采用Raman光谱对样品进行了结构表征,由椭圆偏振光谱仪得到样品的厚度和光学常数,并计算了样品的光学带隙。由变温电导率分析了薄膜的电学输运性质,结果表明,载流子的传输机制为扩展态电导。进而利用变温PL谱研究了薄膜的发光性能,发现其发光峰在1.63 μm处;随着膜厚的减小,峰位和峰形都有改变,且强度明显提高。进一步分析发现,随着膜厚的减小非辐射复合跃迁的激活能增大,从而导致辐射复合过程增强。     

Structural evolution of a-Si:H/SiO2 multilayers upon step by step thermal annealing

a-Si:H/SiO_2 multilayers were prepared by alternatively changing plasma enhanced chemical vapour deposition of a-Si:H layers and in situ plasma oxidation process. Subsequently, as-grown samples were annealed at temperatures from 350℃ to 1100℃ in N_2 ambient with an increment of 100℃. The evolution of bonding configurations and structures with annealing treatments was systematically investigated by Fourier-transform infrared spectroscopy. The peak position of Si－O stretching vibration of SiO_2 layers shift to 1087cm^{-1} after annealing at 1100℃, which demonstrates that the SiO_2 films fabricated by plasma oxidation after high temperature annealing can have similar properties to the thermal grown ones. A Si－O vibration from interfacial SiO_x was identified: the value x was found to increase as increasing the annealing temperature, which is ascribed to the cooperation of hydrogen effusion and reordering of the oxygen bond in SiO_x networks. The H-related bonds were observed in the form of H－Si－O_3 and H－Si－Si_{3-n}O_n (n=1－2) configurations, which are supposed to be present in SiO_2 and interfacial SiO_x layers, respectively. The H atoms bonded in different bonding configurations effuse at different temperatures due to their different desorption energies.     

数学课堂怎样使生成更有价值——一则教学片断与反思

课堂教学是我们实施课改的主阵地,光有良好的课堂教学结构、精辟的问题设计是不够的,自然生成的每一个细节是十分重要的.当前教师对生成出现两种不良倾向,一种是对学生的生成问题不予理睬,或用轻视的态度对待.另一种是对学生的生成问题往往不深入分析,只知道一味肯定学生.     

NiMnCo粉末触媒合成金刚石特征的研究

本文采用扫描电子显微镜(SEM)、图象分析仪和金刚石性能测试仪分别对粉末状和片状NiMnCo触媒合成的金刚石形貌、(111)、(100)结晶面的微形貌、包裹体分布及其力学性能进行分析.研究结果表明:与片状触媒合成的金刚石相比,NiMnCo粉末触媒合成的金刚石呈典型的六-八面体,晶型完整率高;(111)、(100)结晶面完整无缺陷,透明度高、包裹体少且细小分散.因此,NiMnCo粉末触媒合成的金刚石具有较高的静压强度和热稳定性.     

用光学方法研究玻璃微珠电流变液颗粒间的相互作用

运用一套适合研究颗粒间相互作用的双光镊系统,通过对颗粒聚集时间的测量,得出颗粒聚集时间和电场的平方成反比.这是第一次用电流变液颗粒在动态情况下直接验证电偶极子对间的相互作用.发展了一套使用高速CCD摄像机进行扩散波谱(DWS)测量的方法,首次实时测量具有颗粒结构的非各态历经体系的自相关函数,以研究电流变液机理,得到了玻璃微珠电流变液的结构响应时间和力的响应时间;测量了不同电场下体系相关函数的特征衰减时间随时间的变化.在不同电场下测量扩散系数可以反映出相互作用力与电场的平方成正比.     

Sol-gel法制备SO_4~(2-)/ZrO_2-SiO_2及催化合成对硝基苯甲酸甲酯的研究

以ZrOCl2·8H2O和正硅酸乙酯(TEOS)为原料,采用溶胶-凝胶法和透析法制备固体超强酸SO42-/ZrO2-SiO2催化剂,考察了制备条件对硅、锆凝胶化时间的影响,并以合成对硝基苯甲酸甲酯为探针反应,研究了催化剂制备条件对催化活性的影响,最后采用Hammett指示剂法、BET法、FT-IR、TEM和XRD分别对催化剂的酸强度、比表面、反应前后骨架结构和形貌变化、晶相进行了表征。结果表明:(1)当水浴温度为80℃,水10mL时,锆凝胶化时间最短;(2)水浴温度为80℃,水8mL,pH=3.0-4.0时硅凝胶化时间最短;(3)当硅、锆原子摩尔比为10:1,H2SO4浸渍液浓度为1.0mol·L-1,焙烧温度550℃时,催化剂的活性最高,酯产率为70%左右;(4)催化剂酸强度Ho-12.70,反应前后催化剂比表面变化较大且结构形态存在较大差异,催化剂中的SiO2为无定形态,ZrO2为四方晶态。     

Structural and electrical properties of laser-crystallized nanocrystalline Ge films and nanocrystalline Ge/SiN_x multilayers

Nanocrystalline Ge （nc-Ge） single layers and nc-Ge/SiNx multilayers are prepared by laser annealing amorphous Ge （a-Ge） films and a-Ge/SiNx multilayers. The microstructures as well as the electrical properties of laser-crystallized samples are systematically studied by using various techniques. It is found that the optical band gap of nc-Ge film is reduced compared with its amorphous counterpart. The formed nc-Ge film is of p-type, and the dark conductivity is enhanced by 6 orders for an nc-Ge single layer and 4 orders for a multilayer. It is suggested that the carrier transport mechanism is dominant by the thermally activation process via the nanocrystal, which is different from the thermally annealed nc-Ge sample at an intermediate temperature. The carrier mobility of nc-Ge film can reach as high as about 39.4 cm2.V ^-1 .s^-1, which indicates their potential applications in future nano-devices.