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51.
Ch. Srilakshmi E. Widjaja M. Garland B. G. Anderson 《Journal of Raman spectroscopy : JRS》2007,38(3):349-355
Band‐target entropy minimization (BTEM) was applied for the extraction of pure component Raman spectra from samples exhibiting a significant thermal background due to sample emission. In this method, singular value decomposition was first used to calculate the right singular vectors of the spectroscopic data matrix. Then the non‐noise right singular vectors were examined for localized spectral features, which were subsequently used for spectral recovery. These local features were targeted with the BTEM algorithm to recover the pure component Raman spectra. Accordingly, the interfering thermal background was removed. This method of analysis is applied to graphite and barium sulfate Raman spectroscopic data. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
52.
Joseph H. Han Guilian Gao Yuniarto Widjaja Eric Garfunkel Charles B. Musgrave 《Surface science》2004,550(1-3):199-212
Zirconium oxide (ZrO2) is one of the leading candidates to replace silicon oxide (SiO2) as the gate dielectric for future generation metal-oxide-semiconductor (MOS) based nanoelectronic devices. Experimental studies have shown that a 1–3 monolayer SiO2 film between the high permittivity metal oxide and the substrate silicon is needed to minimize electrical degradation. This study uses density functional theory (DFT) to investigate the initial growth reactions of ZrO2 on hydroxylated SiO2 by atomic layer deposition (ALD). The reactants investigated in this study are zirconium tetrachloride (ZrCl4) and water (H2O). Exchange reaction mechanisms for the two reaction half-cycles were investigated. For the first half-reaction, reaction of gaseous ZrCl4 with the hydroxylated SiO2 surface was studied. Upon adsorption, ZrCl4 forms a stable intermediate complex with the surface SiO2–OH* site, followed by formation of SiO2–O–Zr–Cl* surface sites and HCl. For the second half-reaction, reaction of H2O on SiO2–O–Zr–Cl* surface sites was investigated. The reaction pathway is analogous to that of the first half-reaction; water first forms a stable intermediate complex followed by evolution of HCl through combination of a Cl atom from the surface site and an H atom from H2O. The results reveal that the stable intermediate complexes formed in both half-reactions can lead to a slow film growth rate unless process parameters are adjusted to lower the stability of the complex. The energetics of the two half-reactions are similar to those of ZrO2 ALD on ZrO2 and as well as the energetics of ZrO2 ALD on hydroxylated silicon. The energetics of the growth reactions with two surface hydroxyl sites are also described. 相似文献
53.
Yinghuai Z Widjaja E Sia SL Zhan W Carpenter K Maguire JA Hosmane NS Hawthorne MF 《Journal of the American Chemical Society》2007,129(20):6507-6512
Well dispersed ruthenium(0) nanoparticles, stabilized in the ionic liquid agent, trihexyltetradecylphosphonium dodecylbenzenesulfonate, have been successfully prepared via a reduction reaction of the precursor [CpRuCp*RuCp*]PF6 (Cp* = C5Me5). The ruthenium(0) nanoparticles were shown to catalyze the isotope exchange reaction between 10B enriched diborane and natural abundant B10H14 to produce highly 10B enriched (approximately 90%) decaborane(14) products. The ruthenium(0) nanoparticles were characterized by TEM, XRD, and XPS. The 10B enriched decaborane(14) has been analyzed by Raman spectroscopy, NMR, and high-resolution MS. 相似文献
54.
Widjaja T Fitjer L Pal A Schmidt HG Noltemeyer M Diedrich C Grimme S 《The Journal of organic chemistry》2007,72(24):9264-9277
The pseudohelical hydrocarbons (R)-6, (S)-7, and (R)-8 and the helical hydrocarbon (P)-9, formally derived from the helical hydrocarbon (P)-4 by stepwise replacement of each of the four-membered rings by a five-membered ring, have been prepared. Their optical rotations vary systematically, both in magnitude and sign. Of the extremes, (P)-4 represents the usual case of a right-handed dextrorotatory helix, while (P)-9 represents the unusual case of a right-handed levorotatory helix. To rationalize these facts, DFT calculations of the rotatory power of (P)-helices of three-, four-, and five-membered rings have been performed. The results show a very good agreement with the experimental data for the rigid helices of three-membered rings and always show the correct sign and order of magnitude for the flexible helices of four- and five-membered rings for which Boltzmann-averaged optical rotations of up to six conformers had to be used. Within the conformers of the latter, a set of large dihedral angles for the bonds of the inner sphere correspond to a high specific rotation, and a set of small dihedral angles correspond to a low specific rotation. As a consequence, the Boltzmann-averaged values markedly depend on the geometry and weight of the conformers involved. 相似文献