有机非线性光学晶体N-(4-硝基苯基)-L-脯氨醇(NPP)表面结构的AFM研究

本文首次用AFM对非线性晶体的表面结构进行了研究。NPP晶体属单斜晶系,其表面结构与晶面有密切关系。用AFM对其解理(101)面和(001)的研究表明,这两个表面上的分子排列与体相结构一致,未发生重构;在(001)面上分子中的苯环和五元环可被区分开来。用AFM所测得的分子跃迁偶极矩与单斜P2_1晶体结构的二重轴之间的夹角为56°,接近理论值,说明NPP晶体具有很高的宏观二阶非线性活性。这些结果首次在实空间中直接给出了NPP晶体不同晶向的表面结构。     

Experimental Characterization of Correlation—Functions of Random Surfaces by Speckle Measurement and Complementary Algorithm

A method for the extracting the correlation functions of random surfaces is proposed by using the image speckle intensity.Theoretically,we analyse the integral expression of average intensity of the image speckles,and compare it with the pair of Fourier-Bessel-transform-and-the-inversion of the exponential function of the height-height correlation function of the random surfaces.Then the algorithm is proposed numerically to complement the lacking Bessel function factor in the expression of the average speckle intensity,which changes the intensity data into the pair of the Fourier-Bessel-transforn.Experimentally,we measure the average image speckle intensities versus the radius of the filtering aperture in the 4f system and extract the height-height correlation function by using the proposed algorithm.The results of the practical measurements for three surface samples and the comparison with those by atomic force microscopy validate the feasibility of this method.     

Synthesis of Various Types of Silver Nanoparticles Used as Physical Developing Nuclei in Photographic Science

Ag nanoparticles used as physical developing nuclei in photographic science were prepared by reduction method.The as-formed Ag nanoparticle colloid was characterized by UV-Vis absorption spectrum.Atomic Force Microscopy(AFM) and Charge Coupled Device(CCD) technique.It is found that the source of Ag ions,the addition of surfactant and polymer,all have great influence on the size,topography and catalytic activity of Ag nanoparticles.     

Theoretical Study on the Capillary Force between an Atomic Force Microscope Tip and a Nanoparticle

Considering that capillary force is one of the most important forces between nanoparticles and atomic force microscope （AFM） tips in ambient atmosphere, we develop an analytic approach on the capillary force between an AFM tip and a nanoparticle. The results show that the capillary forces are considerably affected by the geometry of the AFM tip, the humidity of the environment, the vertical distance between the AFM tip and the nanoparticle, as well as the contact angles of the meniscus with an AFM tip and a nanoparticle. It is found that the sharper the AFM tip, the smaller the capillary force. The analyses and results are expected to be helpful for the quantitative imaging and manipulating of nanoparticles by AFMs.     

垒掺In提高InGaN/GaN多量子阱发光特性

利用金属有机物化学气相淀积技术在蓝宝石衬底上生长InGaN/GaN多量子阱结构.对多量子阱垒层掺In和非掺In进行了比较研究，结果表明，垒掺In 的样品界面质量变差，但明显增加了光致发光谱的峰值强度和积分强度，带边峰与黄光峰强度之比增大，降低了表面粗糙度.利用这两种结构制备了相应的发光二极管(LED)样品.通过电荧光测量可知，垒掺In的LED比非掺In的LED有较高的发光强度和相对均匀的波长，这主要是由于垒掺In后降低了阱与垒之间晶格失配的应力，从而降低了极化电场，提高了辐射复合效率. 关键词： InGaN/GaN多量子阱 X射线双晶衍射 原子力显微镜 光致发光     

光栅参数测量技术研究进展

光栅参数测量技术是衡量光栅制作水平的重要标准。本文从直接测量法和间接测量法两个角度对现阶段较成熟的光栅参数测量技术进行了研究。重点介绍了原子力显微镜（AFM）测量法、扫描电子显微镜（SEM）测量法、激光衍射（LD）测量法以及散射测量术的测量原理和研究进展,指出了这些方法各自的优缺点和适用范围。AFM测量法和SEM测量法均可测得光栅的局部形貌信息,可用于检测光栅表面形貌缺陷;LD测量法和散射测量术反映的是激光照射区域的平均结果,其中LD测量法能得到光栅周期参数,而椭偏测量术能得到光栅周期以外的其他形貌参数。这些方法测得的光栅参数结果比较吻合,其中LD测量法不确定度最小,AFM次之,SEM最大。文章最后对未来光栅参数测量技术的发展方向进行了论述。     

Gemini表面活性剂与DNA在气/液界面上的相互作用

在气/液界面上, 阳离子表面活性剂可以通过静电作用与阴离子型的脱氧核糖核酸(DNA)分子形成复合膜, 并压缩沉积得到LB(Langmuir-Blodget)膜. 利用表面压-表面积(π-A)曲线、原子力显微镜(AFM)和石英晶体微天平(QCM)研究了阳离子Gemini表面活性剂([C₁₈H₃₇(CH₃)₂N⁺-(CH₂)_s-N⁺(CH₃)₂C₁₈H₃₇]·2Br^-, 简写为18-s-18, s=3, 4, 6, 8, 10, 12)与DNA(双链DNA(dsDNA), 单链DNA(ssDNA))之间的相互作用, 并对18-s-18在不同下相表面的分子面积进行了比较. 实验结果表明连接基团和下相的DNA对Gemini表面活性剂在气/液界面上的性质有很大影响. 此外, Gemini表面活性剂在界面上对DNA的吸附能力与它们之间的相互作用方式密切相关.     

表面活性素单分子膜在空气/水界面的迟滞现象

表面活性素是一类具有较强表面活性的微生物脂肽类化合物,能在空气/水界面形成不溶性单分子膜.利用Langmuir膜天平测定了表面活性素单分子膜的压缩-扩张循环曲线,发现单分子膜在经历了“平台区”后出现较大的迟滞环,迟滞环的形状与亚相pH有关.将“平台区”的单分子膜转移到云母表面后,用原子力显微镜(AFM)和扫描电子显微镜(SEM)均观察到高度达几十至数百纳米的表面聚集体,说明表面活性素在单分子膜的“平台区”伴随着自聚集.研究结果表明,表面活性素单分子膜在空气/水界面的迟滞现象是分子浸入亚相和形成三维表面聚集体共同作用的结果.     

原子力显微镜法研究方解石(104)面的生长及溶解

研究生物矿化过程及生物矿物的形成机制具有重要的科学意义,这方面的研究不仅有助于我们认识自然,而且还可以指导体外仿生合成具有分级结构的功能性复合材料.原子力显微镜(atomic force microscope,AFM)是微米、纳米尺度上实时观测矿物成核或生长的强有力工具.本文综述了原子力显微镜法研究方解石(104)面生...