Nanoclusters of Silicon and Germanium

Synthetic routes for the preparation of Si or Ge nanoclusters as gaseous species, colloids, supported composites, or as unsupported powders are reviewed along with selected characterization data. The optical properties of these and related materials, such as porous Si, are summarized with particular emphasis on photo- or electroluminescence phenomena. Research opportunities related to Si and Ge cluster chemistry are suggested.     

一种非晶硅膜改性弹性玻璃毛细管交联中等极性固定相色谱柱的制备

研究了非晶硅膜改性的弹性玻璃毛细管交联ＯＶ－１７０１中等极性固定相色谱柱。在适当温度下，采用过氧化二异丙苯（ＤＣＵＰ）游离基引发交联ＯＶ－１７０１固定液，成功地制备了交联ＯＶ－１７０１柱，该柱具有柱效高、惰性好、耐溶剂、抗腐蚀和耐高温等性能，是一种新型高性能的中等极性交联柱。     

Recent advances in the activation of boron and silicon reagents for stereocontrolled allylation reactions

Despite the popularity of boron and silicon allylation reagents in stereocontrolled synthesis, they suffer from a number of inherent limitations that have slowed down their development as synthetic tools for nucleophilic additions to carbonyl compounds and imine derivatives. These limitations are the low reactivity and diastereoselectivity of allyl trialkylsilane reagents, and the lack of catalytic systems for the activation and substoichiometric control of enantioselectivity in the additions of allyl boron reagents. To develop more efficient and general methods for the control of absolute stereochemistry in the resulting homoallylic alcohols, new approaches aimed at solving the problem of activation of allylic boron and silicon reagents are needed. This Minireview describes a number of recent approaches that have been devised to address this problem.     

Adsorption of triethygermane on Si(100): thermal and nonthermal channels for ethyl ligand removal/dissociation

Adsorption of triethylgemane (TEG) on the Si(100) surface at 100 K has been studied using a variety of surface‐sensitive spectroscopies. Thermally and electronically desorbed species were analyzed using temperature‐programmed desorption (TPD) and electron‐stimulated desorption (ESD) techniques. Electronically desorbed ions (H⁺) were analyzed using a time‐of‐flight technique (TOF) and time evolution studies were conducted on desorbing neutral species. Direct analysis of surface species were carried out using X‐ray photoelectron spectroscopy (XPS) and high‐resolution electron energy loss (HREELS) spectroscopy. Evidence is offered for (1) an electron‐induced channel for direct ethylene desorption via a β‐hydride elimination process; (2) an electron‐stimulated transfer of ethyl ligands from a Ge to a Si site; and (3) both thermal‐ and electron‐stimulated desorption of methyl groups. Copyright © 2006 John Wiley & Sons, Ltd.     

Synthesis of Ultrafine SiC Powders from Carbon-Silica Hybridized Precursors with Carbothermic Reduction

Inorganic-organic hybrid gels were prepared by simultaneous condensation of the liquid mixture of ethyl silicate, ethyl borate and water soluble phenol resin with low molecular weight. The liquid mixtures were changed into lightly colored transparent gels after a catalyst addition and stirring. The obtained gels were crushed, dried and fired in controlled conditions to yield the inorganic precursors. Since the tailored inorganic precursors mainly consisted of SiO2 and carbon, silicon carbide was formed with the heat treatments in an Ar atmosphere beyond 1773 K with carbothermic reduction. The properties and morphology of the formed silicon carbide powders in terms of the starting precursor compositions and the conditions of the carbothermic reduction were investigated with SEM, XRD and TG-DTA analysis.     

三甲基硅基化反应的研究

本文研究了以水玻璃作为硅酸盐阴离子,按Lentz方法进行的三甲基硅基化反应。在改变反应克分子比例时,可得到不同分子量和硅基化程度的硅树脂,由此说明,在硅基化反应时可能发生聚合、解聚和水解等副反应。对影响硅树脂产率的反应条件和三甲基硅基化树脂的一些物理性质也进行了讨论。     

烷类特种气体分析装置的研制及其应用

研制烷类特种气体分析专用的多维气相色谱仪，特制的热导检测器，具有手动－自动功能。设计了输气－配气装置和多维气相色谱流程。以微机控制，可按编辑程序清洗系统。检查本底，自动进样，显示或打印谱图和分析结果。可检测多种烷类特种气体组份及其中氧，氮，一氧化碳和甲烷等痕量杂质。     

Synthesis of anodic silicon oxide films in water-organic solutions containing orthophosphoric acid

Variations in electrophysical properties of anodic silicon oxide at the surface of semiconductor silicon are studied as a function of the composition of electrolytic solutions containing orthophosphoric acid and the conditions of reaching the final formation potential. The optimum conditions for the formation of anodic SiO₂ coatings that include phosphorus-containing admixtures are determined, the coatings being intended for application as diffusates in nanoelectronics.     

Growth of silicon thin film by LPE on porous silicon bilayers

The fabrication of solar cells based on the transfer of a thin silicon film on a foreign substrate is an attractive way to realise cheap and efficient photovoltaic devices. The aim of this work is to realise a thin mono-crystalline silicon film on a double porous silicon layer in order to detach and transfer it on mullite. The first step is the fabrication of a double porous silicon layer by electrochemical anodisation using two different current densities. The low current leads to a low porosity layer and during annealing, the recrystallisation of this layer allows epitaxial growth. The second current leads to a high porosity which permits the transfer on to a low cost substrate. Liquid Phase Epitaxy (LPE) performed with indium (or In+Ga) in the temperature range of 950–1050°C leads to almost homogeneous layers. Growth rate is about 0.35 μm min⁻¹. Crystallinity of the grown epilayer is similar on porous silicon and on single crystal silicon. In this paper, we focus on the realisation of porous silicon sacrificial layer and subsequent LPE growth. This revised version was published online in July 2006 with corrections to the Cover Date.