Controlled Synthesis of Ag2S,Ag2Se,and Ag Nanofibers by Using a General Sacrificial Template and Their Application in Electronic Device Fabrication

Nanofiber bundles of Ag₂S, Ag₂Se, and Ag have been successfully synthesized by making use of Ag₂C₂O₄ template nanofiber bundles, utilizing both anion‐exchange and redox reactions. The obtained bundles were polycrystalline nanofibers composed of nanoparticles in which the precursor morphology was well‐preserved, indicating that Ag₂C₂O₄ nanofiber bundles acted as a general sacrificial template for the synthesis of silver‐based semiconductor and metal nanofibers. Dispersing media and transforming reactants were found to be key factors influencing the chemical transformation in the system. In particular, separate single‐crystalline Ag nanofibers were obtained via a nontemplate route when ascorbic acid was used as a relatively weak reductant. An electrical transfer and switching device was built with the obtained Ag₂S and Ag nanofiber bundles, utilizing the unique ion‐conductor nature of Ag₂S and revealing their potential applications in electronics.     

Selective area epitaxy of CdTe

We have performed selective area epitaxy (SAE) of CdTe layers grown by molecular beam epitaxy using a shadow mask technique. This technique was chosen over other SAE techniques due to its simplicity and its compatibility with multiple SAE patterning steps. Features as small as 50 microns × 50 microns were obtained with sharp, abrupt side walls and flat mesa tops. Separations between mesas as small as 20 microns were also obtained. Shadowing effects due to the finite thickness of the mask were reduced by placing the CdTe source in a near normal incidence position. Intimate contact between the mask and the substrate was essential in order to achieve good pattern definition.     

From the individual element test to finite element templates: Evolution of the patch test

This paper starts a sequence of three articles that follow an unconventional approach in finite element research. The ultimate objective is to construct high-performance elements and element-level error estimators for those elements. The approach takes off from our previous work in high-performance elements and culminates with the development of finite element templates. The present paper concentrates on the patch test and evolved versions of the test that have played a key role in this research. Following a brief review of the historical roots, we present the Individual Element Test (IET) of Bergan and Hanssen in an expanded context that encompasses several important classes of new elements. The relationship of the IET to the multielement forms A, B and C of the patch test and to the single-element test are investigated. An important consequence of the IET application is that the element stiffness equations decompose naturally into basic and higher-order parts. The application of this decomposition to the “sanitization” of the non-convergent BCIZ element is described and verified with numerical experiments. Two sequel papers in preparation are subtitled ‘the algebraic approach’ and ‘element-level error estimation’. These apply the fundamental decomposition to the derivation of templates for specific mechanical elements and to the construction of element-level error estimators, respectively.     

Elimination of dislocations in heteroepitaxial MBE and RTCVD Ge x Si1-x grown on patterned Si substrates

We have grown Ge _x Si_1-x (0 <x < 0.20,1000–3000Å thick) on small growth areas etched in the Si substrate. Layers were grown using both molecular beam epitaxy (MBE) at 550° C and rapid thermal chemical vapor deposition (RTCVD) at 900° C. Electron beam induced current images (EBIC) (as well as defect etches and transmission electron microscopy) show that 2800Å-thick, MBE Ge_0.19Si_0.81 on 70-μm-wide mesas have zerothreading and nearly zero misfit dislocations. The Ge_0.19Si{0.81} grown on unpatterned, large areas is heavily dislocated. It is also evident from the images that heterogeneous nucleation of misfit dislocations is dominant in this composition range. 1000Å-thick, RTCVD Ge_0.14Si_0.86 films deposited on 70 μm-wide mesas are also nearly dislocation-free as shown by EBIC, whereas unpatterned areas are more heavily dislocated. Thus, despite the high growth temperatures, only heterogeneous nucleation of misfit dislocations occurs and patterning is still effective. Photoluminescence spectra from arrays of GeSi on Si mesas show that even when the interface dislocation density on the mesas is high, growth on small areas results in a lower dislocation density than growth on large areas.     

New approach for the preparation of nanoporous polyorganosilicate low‐k films

The distribution of pores and the mechanical properties of materials are the key factors in preparing satisfactory low‐k films. In the present study, a kind of silsesquioxane‐polyethylene glycol (SSQ‐PEG) was synthesized and used as a template to make the distribution of pores more even in the low‐k films. The crosslinking density of films could be adjusted by the sol‐gel of tetramethoxysilane/dimethoxydimethylsilane with various proportions. The porosity of films could also be adjusted with different proportions of pendant PEG chains introduced. A dielectric constant as low as 2.1 had been achieved for nanoporous polyorganosilicate films with good tenacity. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1238–1243, 2007     

“A+一+X,B+一+Y”构式的分类及释义模板

该文以现代汉语中的“A+一+X,B+一+Y”格式为例,介绍了构建《现代汉语构式知识库》的初步工作。“A+一+X,B+一+Y”格式可根据其表义功能不同分为三个大类,十个小类。该文重点阐释了该构式表达“因果倚变义、事物交错义、状态交替义、动作行为交替义、周遍大量义、让步小量义”等6种意义的判定条件及相应的释义模板。     

基于规则的汉语名名组合的自动释义研究

该文以现代汉语(特别是网络搜索词)中的名名组合为主要研究对象,探索一种基于规则的汉语名名组合的自动释义方法。其研究步骤为: (1)利用《现代汉语语义词典》中名词的语义类别,来建立名名组合的语义类组合模式;(2)在“生成词库论”中物性角色思想的指导下,用名名组合中某个名词的施成角色或功能角色作为释义动词,来揭示这两个名词之间的语义关系;(3)以语义类组合模式为单位构建名名组合的释义模板,并汇集成名名搭配数据库;(4)利用《知网》资源,来获取具体名词的施成角色和功能角色,建立汉语名词知识库。在这两个数据库的基础上,我们初步实现了一个汉语名名组合的自动释义程序。     

Fabrication and optical characterization of poly(2,5‐di‐n‐butoxyphenylene) nanofibril arrays

Anodic aluminum oxide (AAO) membrane can be used as template for the synthesized nanostructures. In this article, we have prepared the AAO membrane by using electrooxidation of aluminum substrate in phosphoric acid, and fabricated poly(2,5‐di‐n‐butoxyphenylene) (BuO–PPP) nanofibril arrays by oxidative coupling polymerization of 1,4‐di‐n‐butoxybenzene (DBB) within the pores of the AAO template membrane. The detailed molecular structure of the polymer nanofibrils was characterized by using infrared and ¹H nuclear magnetic resonance spectra, and estimated to consist of almost equal fractions of 1,4‐ and 1,3‐ linkages. We have used transmission electron microscopy, scanning electron microscopy, and atom force microscopy to confirm the morphologies and images of the AAO template membrane and the fabricated nanometer scale of BuO–PPP nanofibril arrays. The experimental results demonstrated that the pores of the AAO membrane were regular and uniform, and parallel each other, and the BuO–PPP chains in the narrowest template‐synthesized nanofibrils were oriented parallel to the porous axes of the AAO membrane and perpendicular to the surface of the aluminum substrate. The polymer chain orientation was partially responsible for the enhanced conductivity. The ultraviolet absorption spectrum of the BuO–PPP nanofibril arrays shown that the polymer contains a better extended π‐conjugation system along poly‐(p‐phenylene) backbone, which resulted in longer wavelength shift of the absorption band, the absorption maxima were located at 258 nm (E₁ absorption band) and 332 nm (E₂ absorption band), respectively. Photoluminescence spectrum of the BuO–PPP nanofibril arrays exhibited a blue emission. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 425–430, 2004     

Determination of Both Mesopores and Macropores in Three-Dimensional Ordered Porous Materials by Nitrogen Adsorption

Three-dimensionally ordered silica structures containing both mesopores and macropores are created using polystyrene coacervate spheres with a diameter of ca. 146 nm. The close-packed polystyrene coacervate spheres are intercalated with tetraethyl orthosilicate. The spheres are removed by calcination leaving an inverse silica replica with a spherical macropore cavity diameter of 110 nm. Due to the nature of these porous structures, pores leading into the macropore cavity are in the mesopore regime, 40 nm in diameter. The nitrogen adsorption data described in the following paper gives a pore size for both the macropore cavity and the mesopore openings leading into the cavity. The pore sizes as determined by nitrogen sorption are in good agreement with the pore sizes observed by scanning electron microscopy. Mercury intrusion porosimetry results confirm the size of the mesopore openings leading into the macropore cavity, however due to destruction of the sample upon intrusion, extrusion results can not be obtained to determine main cavity diameters. As a result, nitrogen sorption may be a viable option for determining pore sizes with these three-dimensionally ordered materials containing both mesopores and macropores.     

Formation mechanism of subtrenches on cone-shaped patterned sapphire substrate

In this paper, the cone-shaped patterned sapphire substrates (PSS) were etched by an inductively couple plasma with BCl 3 as the reacting gas. The influence of the operating pressure and the RF bias power on subtrenches of the cone-shaped PSS and the formation mechanism of subtrenches were investigated. The profiles of patterns were characterized by FESEM (field emission scanning electron microscope). It showed that the subtrench size varied with the operating pressure and the RF bias power. As the operatin...