共查询到20条相似文献,搜索用时 15 毫秒
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R. Navamathavan 《Applied Surface Science》2007,253(21):8788-8793
Low dielectric constant SiOC(H) films are deposited on p-type Si(100) substrates by plasma enhanced chemical vapor deposition (PECVD) using methyltriethoxysilane (MTES, C7H18O3Si) and oxygen gas as precursors. The SiOC(H) films are deposited at room temperature, 100, 200, 300 and 400 °C and then annealed at 100, 200, 300 and 400 °C temperatures for 30 min in vacuum. The influence of deposition temperature and annealing on SiOC(H) films are investigated. Film thickness and refractive index are measured by field emission scanning electron microscopy and ellipsometry, respectively. Chemical bonding characteristics of as-deposited and annealed films are investigated by Fourier transform infrared (FTIR) spectroscopy in the absorbance mode. As more carbon atoms are incorporated into the SiOC(H) films, both film density and refractive index are decreased due to nano pore structure of the film. In the SiOC(H) film, CH3 group as an end group is introduced into OSiO network, thereby reducing the density to decrease the dielectric constant thereof. The dielectric constant of SiOC(H) film is evaluated by C-V measurements using metal-insulator-semiconductor (MIS), Al/SiOC(H)/p-Si structure and it is found to be as low as 2.2 for annealed samples deposited at 400 °C. 相似文献
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Xiuqin Chen 《Applied Surface Science》2008,254(20):6693-6696
Fabrication of PF-codoped TiO2 nanotubes was carried out using a one-step electrochemical anodization process by tailoring the composition of the electrolyte with the aim of PF-codoping to extend the optical absorption of TiO2 to the visible-light region. The as-prepared PF-codoped TiO2 nanotubes were characterized by SEM, XPS, and UV-vis diffuse reflectance absorption spectra (DRS). The results showed that the tube diameter of the nanotubes was approximately 100 nm and the tube length was approximately 510 nm. The phosphorus and fluorine were successfully doped into TiO2 nanotubes, as evidenced by XPS. Moreover, the PF-codoped samples displayed remarkably strong visible-light response. 相似文献
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Poly(ethylene terephthalate) (PET) films were treated with CF4 plasma immersion. The samples were processed at different RF powers and treatment time. The surface modification of PET films was evaluated by water contact angle (CA), X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM). Decrease in contact angle of both sides of PET films was observed under mild treatment conditions. However, as raising treatment power and/or time, the change in contact angle between the two sides of PET films was different. The relatively hydrophobic and hydrophilic surfaces were being in situ formed on the two sides of PET films, respectively. And the extreme values of water contact angle reached 108.63 and 7.56°, respectively. XPS analyses revealed that there was a substantial incorporation of fluorine and/or oxygen atoms in both side surfaces. The relative chemical composition of the C (ls) spectra's showed the incorporation of non-polar fluorine-based functionalities (i.e. CFCFn, CF2 or CF3 groups) and polar oxygen-based functionalities (i.e. COOH or OH groups) in the surfaces. Correlation between the plasma parameters and the surface modification of PET films is also discussed. 相似文献
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Porous silicon (PS) was passivated by silica film using a sol-gel method; the photoluminescence (PL) properties were significantly improved; namely, PL intensity and stability increased and PL peak shifted to shorter wavelength. Scanning electron microscope (SEM) and Fourier transformed infrared spectroscope (FTIR) results indicated that silica passivation produced a compact film on the PS surface and modified the surface state of PS. The number of stable surface bonds (HSiO3, HSiSiO2 and H2SiO2) increased due to the oxidation of SiH back-bonds during the gelation process, and thus the PL intensity and stability were improved. Moreover, the blue-shift of PL peak was determined due to the increase in the ratio of SiO/SiH. 相似文献
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Ying Wu 《Applied Surface Science》2006,252(14):5220-5226
Nanosized TiNiO catalysts prepared by a modified sol-gel method have been investigated in the oxidative dehydrogenation of propane (ODP) to propene. At 300 °C the yield to propene of 12.1% was obtained on 9.1 wt.% TiNiO catalyst with the selectivity of 43%. The continued variety of lattice parameter and variation of chemical value of nickel and titanium ion on the surface indicates that there are strong interactions of TiO2 and NiO. The decreased low temperature oxygen desorption and the weaker reducibility seems to be responsible for the decreased activity and enhanced selectivity of propane oxidative dehydrogenation over TiNiO catalysts. 相似文献
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Xugeng Guo 《Journal of Molecular Spectroscopy》2009,256(2):242-246
Geometries and stabilities of the linear aluminum-bearing carbon chains AlC2nH (n = 1-5) in their ground states have been explored by the DFT-B3LYP and RCCSD(T) methods. Structures of the X1Σ+ and 11Π electronic states have also been optimized by the CASSCF approach. The studies indicate that these species have single-triple bond alternate pattern, AlCCCC?CCH, and the electronic excitation from X1Σ+ to 11Π leads to the shortening of the AlC bonds. The vertical excitation energies of the 11Π ← X1Σ+ and 21Π ← X1Σ+ transitions for AlC2nH (n = 1-5) have been investigated by the CASPT2, EOM-CCSD, and TD-B3LYP levels of theory with the cc-pVTZ basis set, respectively. CASPT2-predicted 11Π ← X1Σ+ transition energies are 3.57, 3.44, 3.33, 3.26, and 3.21 eV, respectively. For AlC2H, our estimate agrees very well with the experimental value of 3.57 eV. In addition, the AlC bond dissociation energies and the exponential-decay curves for these vertical excitation energies are also discussed. 相似文献
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Bianca Montanari Sidney J.L. Ribeiro Gaël Poirier Máximo S. Li 《Applied Surface Science》2008,254(17):5552-5556
Thin films were prepared using glass precursors obtained in the ternary system NaPO3BaF2WO3 and the binary system NaPO3WO3 with high concentrations of WO3 (above 40% molar). Vitreous samples have been used as a target to prepare thin films. Such films were deposited using the electron beam evaporation method onto soda-lime glass substrates. Several structural characterizations were performed by Raman spectroscopy and X-ray Absorption Near Edge Spectroscopy (XANES) at the tungsten LI and LIII absorption edges. XANES investigations showed that tungsten atoms are only sixfold coordinated (octahedral WO6) and that these films are free of tungstate tetrahedral units (WO4). In addition, Raman spectroscopy allowed identifying a break in the linear phosphate chains as the amount of WO3 increases and the formation of POW bonds in the films network indicating the intermediary behavior of WO6 octahedra in the film network. Based on XANES data, we suggested a new attribution of several Raman absorption bands which allowed identifying the presence of WO− and WO terminal bonds and a progressive apparition of WOW bridging bonds for the most WO3 concentrated samples (above 40% molar) attributed to the formation of WO6 clusters. 相似文献
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The chemical properties of AlxGa1−xN surfaces exposed to air for different time periods are investigated by atomic force microscopy (AFM), photoluminescence (PL) measurement and X-ray photoelectron spectroscopy (XPS). PL and AFM results show that AlxGa1−xN samples exhibit different surface characteristics for different air-exposure times and Al contents. The XPS spectra of the Al 2p and Ga 2p core levels indicate that the peaks shifted slightly, from an AlN to an AlO bond and from a GaN to a GaO bond. All of these results show that the epilayer surface contains a large amount of Ga and Al oxides. 相似文献
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G.S. Grubbs II A. King W.C. Bailey S.A. Cooke 《Journal of Molecular Spectroscopy》2010,263(2):127-134
A potential energy scan of chlorodifluoroacetyl chloride, CF2ClC(O)Cl, at the MP2/6-311+G(d) level of theory predicts stable gauche and trans conformers, with Egauche<Etrans. Ab initio calculations were made of approximate equilibrium structures of these and, on these structures, calculations were made of 35Cl and 37Cl nuclear quadrupole coupling constant tensors. Coupling constants here predicted, as well as rotational constants and molecular dipole moments, are applied to aid analyses of experimental microwave spectra. Chirped pulse Fourier transform microwave spectroscopy has been used to rapidly record the rotational spectra of four isotopologues of the title molecule, CClF2C(O)Cl, namely 35Cl35Cl, 35Cl37Cl, 37Cl35Cl, and 37Cl37Cl. Only the gauche conformer was observed under the experimental conditions. For the four isotopologues a total of 464, 219, 197, and 77 transitions have been recorded, respectively. With the exception of the 37Cl37Cl isotopologue sufficient data was available to determine all Cl quadrupole coupling tensors. Comparisons between the theoretical and experimental results are made. 相似文献
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D.K. Havey 《Journal of Molecular Spectroscopy》2004,228(1):152-159
This work investigates the vibrational spectroscopy of a series of organic acids, CH3(CH2)nCOOH (n = 1-5), previously unobserved in the IR and near-IR (2000-15 000 cm−1). The work obtains frequencies and relative intensities for all OH and CH stretching transitions. Comparison of the frequencies and intensities of CH and OH stretching transitions reveal interesting trends in acid chain length that are discussed. Literature values for acetic acid (CH3COOH) and formic acid (HCOOH) are used to gain a broader understanding for the spectroscopy of the organic acids CH3(CH2)nCOOH. The observation of several combination bands involving the CH and OH stretching vibrations and possible rotational isomer and hot band transitions are reported. 相似文献
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Kibyung Park 《Applied Surface Science》2008,254(6):1842-1846
Various amounts of H-termination on a Ge surface were prepared by dipping a Ge wafer in differentially diluted hydrofluoric acid solutions for different periods of time. Formation of GeHx in hydrofluoric acid and its disappearance in hydrochloric acid (HCl) were directly measured by using multiple internal reflection Fourier transform infrared spectroscopy (MIR FT-IR). Peak intensity of GeHx vibration mode was increased with diluted hydrofluoric acid (DHF) treatment time and the concentration of HF solution. Therefore, it is suggested that microroughness of a Ge surface changes depending on the concentration of HF. Peak intensity of GeHx vibration mode was reduced when the GeHx surface was treated in HCl solution. With an increase in HCl treatment time, peak intensity of GeHx vibration mode was reduced. Ge surfaces treated in a more diluted HF solution were barely modified, because it was thought to have fewer kink sites, dihydrides and trihydrides. 相似文献