Desorption/ionization on porous silicon mass spectrometry (DIOS) of model cationized fatty acids

Desorption/ionization on porous silicon (DIOS) is a very useful technique in the case of small molecular weight compounds, compared to the matrix-assisted laser desorption ionization (MALDI). This is because MALDI generates matrix-related ions that overlap with the mass range of interest. The aim of our work was to investigate the suitability of the DIOS technique in the case of fatty acids in negative ion mode. The analysis of the chosen fatty acid models, nonadecanoic acid (C(19)H(38)O(2)) and heneicosanoic acid (C(21)H(42)O(2)), gave rise to the observation of the deprotonated monomeric species and selective cationized multimeric species. This cation selectivity was further elucidated by complementary studies based on the addition of various metals such as Ag(I), Zn(II), Fe(II), and also Cu(II). Specific behavior, depending upon the introduced metal, was highlighted by different redox reaction processes and also metastable decompositions (in PSD mode).     

Silicon-phthalocyanine-cored fullerene dendrimers: synthesis and prolonged charge-separated states with dendrimer generations

Silicon-phthalocyanine-cored fullerodendrimers with up to eight fullerene substituents (SiPc-n C(60); n=2, 4, and 8) have been synthesized. Photophysical properties of newly synthesized SiPc-n C(60) have been investigated by time-resolved fluorescence and transient absorption analysis with pulsed laser light. Laser photolysis measurements suggest the occurrence of a charge-separation process from (1)SiPc* to the C(60) subunits. The nanosecond transient absorption spectra in the near-IR region indicate that the lifetimes of the formed radical ion pairs are prolonged on the order of SiPc-8 C(60)>SiPc-4 C(60)>SiPc-2 C(60), which may be related to the electron migration among the C(60) subunits. The usefulness of SiPc-n C(60) as light-harvesting systems, evaluated as a ratio of the rates of charge recombination to those of charge separation, increases markedly with the dendrimer generation.     

多孔硅的表面碳膜钝化

报道对多孔硅（ＰＳ）进行碳膜（ＣＦ）钝化处理的结果。红外吸收光谱表明,经钝化处理样品的表面由Ｓｉ－Ｃ、Ｓｉ－Ｎ和Ｓｉ－Ｏ键所覆盖;荧光我谱表明,经钝化处理的样品较未处理的样品发光强度提高４￣４．５倍,且发光峰位明显蓝移;存放实验显示,经钝化处理的样品发光强度稳定、发光峰位不变。这些结果表明正丁胺可以在多孔硅表面形成优良的钝化碳膜,是一种十分有效的多孔硅后处理途径。     

硅纳米线拉曼光谱的波长选择效应

我们用四种不同波长的激光作为激发源研究硅纳米线的拉曼谱 ,观察到一种反常的现象 ,即拉曼峰的频移、峰宽和非对称系数都依赖于激发光波长。考虑了量子限制效应 ,样品的尺寸分布和共振拉曼散射特性 ,对此反常现象提出了一个合理的解释     

发光多孔硅的光谱及电化学研究

单晶硅是E_g为1.1eV的间接带隙半导体材料,在可见光区不发光,不能应用于光电子领域.但是,Canham 1990年首次发现^[1],适当条件下形成的多孔硅在室温下就可发出强度能与Ⅲ-Ⅴ族半导体发光二极管相媲美的可见光。     

聚硅氧烷负载硫、氮-铂双齿配合物的合成及其对烯烃硅氢化的催化作用

γ-巯丙基三甲氧基硅烷与β-氯乙基二甲胺盐酸盐在甲醇钠存在下缩合,得到4-硫杂-6-二甲胺基己基三甲氧基硅烷。后者以气相法二氧化硅固载,再与氯亚铂酸钾反应,合成了二氧化硅固载的聚-4-硫杂-6-二甲胺基己基硅氧烷-铂配合物。它是烯烃硅氢加成的有效催化剂。     

半导体晶片Fe/Ni玷污的紫外荧光谱研究

针对Si,GaAs半导体晶片中金属杂质玷污的问题,本文提出了紫外光致荧光谱的检测方法。常温下,晶片中的Fe,Ni杂质玷污可产生紫外特征荧光峰。这种新的检测方法是非破坏性的,并适用于φ76.2mm,φ100mm大圆片的直接检验,而且具有较高的检测灵敏度。     

生物活性含硅有机锡化合物的研究

对近年来含硅有机锡化合物的进展进行了综述,结构和活性关系的研究表明化合物的生物活性主要取决于硅原子上的取代基,生物活性大小顺序为:(Me₃SiCH₂)₃SnY>>(PhMe₂SiCH₂)₃SnY＞(Ph₂MeSiCH₂)₃SnY,(PhCH₂Me₂SiCH₂)₃SnY.     

Spatially resolved evaluation of power losses in industrial solar cells by illuminated lock‐in thermography

The principles of a recently introduced measurement technique for power losses in solar cells, illuminated lock‐in thermography (ILT), are reviewed. The main advantage of ILT over dark lock‐in Thermography (DLT) is measurement under realistic operational conditions of solar cells. The main focus of this paper is to demonstrate the wide range of applications of ILT in identifying the causes of power losses in solar cells. For this purpose different evaluation methods are presented. A method for the evaluation of improvement potentials within a given cell technology is demonstrated. It is shown that different types of series resistance may be localized. Small areas of recombination losses (e.g., grain boundaries) can routinely be detected, which is not possible in dark lock‐in thermography. Good correspondence with light‐beam‐induced current images is found. A realistic evaluation of the impact of recombination losses on solar cell performance is demonstrated on two examples. Finally, process‐ or treatment‐induced recombination losses are investigated. In summary ILT is shown to be an extremely powerful tool in localizing, identifying and quantifying power losses of solar cells under realistic illumination conditions. Copyright © 2004 John Wiley & Sons, Ltd.     

Base doping and recombination activity of impurities in crystalline silicon solar cells

The optimisation of base doping for industrial crystalline silicon solar cells is examined with model calculations. Focus is on the relation between base doping and carrier recombination through the important impurities interstitial iron (Fe_i) and the metastable boron–oxygen (BO) complex. In p‐type silicon, the optimum base resistivity is strongly dependent on defect concentration. In n‐type silicon, recombination due to Fe_i is much lower and nearly independent of resistivity. Fe_i is likely representative for other transition metal impurities. In many real cells a balance between Fe_i or similar defects, and BO will occur. Copyright © 2004 John Wiley & Sons, Ltd.