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81.
A quantitative analysis of the surface density of amine groups on a plasma-polymerized ethylenediamine thin film deposited on a platinum surface using inductively coupled plasma chemical vapor deposition method is described. UV-visible spectroscopy together with a chemical derivatization technique using Fourier transform infrared (FT-IR) spectroscopy was used to obtain the quantitative information. Chemical tags of pentafluorobenzaldehyde were hybridized with the surface amine groups and were easily detected due to the characteristic absorption bands of C-F stretching, aromatic ring and CN stretching vibrations in the reflection-absorption FT-IR spectra. The surface amine density was reproducibly controlled as a function of deposition plasma power and quantified using UV-visible spectroscopy. A good linear correlation was observed between the FT-IR intensities of the characteristic absorption bands and the surface amine densities, suggesting the possibility of using this chemical derivatization technique to quantify the surface densities of specific functional groups on an organic surface. Chemical derivatization was also used with X-ray photoelectron spectroscopy on the same samples, and the results were compared with those obtained from FT-IR and time-of-flight secondary ion mass spectrometry. Although each analysis technique has different probing depths from the surface, the three different data sets obtained from the chemical tags correlated well with each other since each analysis technique measured the chemical tags on the sample surface. 相似文献
82.
Yong Sun Won Sung Soo Park Young Seok Kim Timothy J. Anderson Lisa McElwee-White 《Journal of Crystal Growth》2009,311(14):3587-3591
DFT calculations were employed to investigate transamination during metalorganic chemical vapor deposition (MOCVD) of transition metal nitrides films, such as titanium nitride (TiN) and tantalum nitride (TaN). The calculated energetics and rate constants for the ligand exchange of tert-butylimidotris(dimethylamido) tantalum (TBTDMT) with NH3 demonstrated that NH3 addition to form the ammonia adduct, TBTDMT·NH3, proton transfer and dissociation of dimethylamine to afford net transamination of the dimethylamido ligand are facile even at low temperature (∼300 °C). The transamination of the tert-butylimido ligand, however, was relatively slow at those temperatures but became facile at temperatures appropriate for CVD growth (∼600 °C). Rapid transamination is consistent with lower temperature for growth of TaN by MOCVD in the presence of NH3, efficient removal of carbon-containing ligands, and incorporation of higher levels of nitrogen in the resulting films. 相似文献
83.
J. Hayoz M. Bovet T. Pillo L. Schlapbach P. Aebi 《Applied Physics A: Materials Science & Processing》2000,71(6):615-618
We demonstrate a very simple and reliable method of manufacturing clean, single-crystalline Y2O3 films on Nb(110) substrates in situ. The method exploits the oxygen bulk contamination of Nb as a source of clean oxygen.
For substrate temperatures above 800 K oxygen segregation to the Nb surface is so efficient, that yttrium becomes oxidized
during deposition without any background oxygen pressure required in the ultrahigh vacuum system. The crystallinity and stoichiometry
of these films can be tuned by the deposition temperature. For Y deposition at 1300 K the formation of well-ordered (111)-oriented
Y2O3 films is achieved.
Received: 19 April 2000 / Accepted: 20 April 2000 / Published online: 23 August 2000 相似文献
84.
Polarized Fourier Transform Infrared (FTIR) spectroscopy is employed to study structure-property relationships in major ampullate
spider silk being exposed to an external mechanical strain. From the measured infrared dichroism of aminoacid-residue - specific
bands the molecular order parameter, the frequency width at half-maximum (FWHM) and the spectral position of the absorption
maximum are determined in dependence on the external strain. For the highly ordered alanine-rich β sheets a change in the
vibrational potential is found for macroscopic strains as low as a few percent. It can be quantitatively described by a quantum-mechanical approach in which the mechanical strain is treated as a weak
external perturbation. The immediate microscopic response to the external field proves that β -sheeted crystals are tightly
interconnected by pre-stretched chains as suggested recently (Y. Liu et al., Nat. Mater. 4, 901 (2005)). 相似文献
85.
L. Menzel A.A. Kosterev R.F. Curl F.K. Tittel C. Gmachl F. Capasso D.L. Sivco J.N. Baillargeon A.L. Hutchinson A.Y. Cho W. Urban 《Applied physics. B, Lasers and optics》2001,72(7):859-863
Two configurations of a continuous wave quantum cascade distributed feedback laser-based gas sensor for the detection of NO
at a parts per billion (ppb) concentration level, typical of biomedical applications, have been investigated. The laser was
operated at liquid nitrogen temperature near λ=5.2 μm. In the first configuration, a 100 m optical path length multi-pass
cell was employed to enhance the NO absorption. In the second configuration, a technique based on cavity-enhanced spectroscopy
(CES) was utilized, with an effective path length of 670 m. Both sensors enabled simultaneous analysis of NO and CO2 concentrations in exhaled air. The minimum detectable NO concentration was found to be 3 ppb with a multi-pass cell and 16 ppb
when using CES. The two techniques are compared, and potential future developments are discussed.
Received: 1 November 2000 / Revised version: 19 January 2001 / Published online: 20 April 2001 相似文献
86.
本文研究了Je(s)manowicz于1956年提出的关于丢番图方程(1.1)解的猜想.利用数论中的一些方法,得到了丢番图方程(1.2)的所有正整数解,证明了Je(s)manowicz猜想在这类情况下的正确性. 相似文献
87.
Determination of Astrophysical 13N(p,γ)14O S-factors from the Asymptotic Normalization Coefficient of )14C → 13C + n 下载免费PDF全文
The angular distribution of the 13C(d,p)14C reaction is reanalysed using the Johnson--Soper approach. The squared asymptotic normalization coefficient (ANC) of virtual decay 14C →13C + n is then derived to be 21.4 ± 5.0fm-1. The squared ANC and spectroscopic factor (SF) of 14O → 13N + p are extracted to be 30.4 ± 7.1fm-1 and 1.94 ± 0.45, respectively. The astrophysical S-factors and reaction rates of 13N(pγ)14O are determined from the ANC of 14O → 13N + p using the R-matrix approach. 相似文献
88.
A confocal Raman investigation of Pb1 − xLaxTi1 − x/4O3 (PLT) thin films grown by RF magnetron sputtering on PbOx/Pt/Ti/SiO2/Si substrates with an intermediate LaSrCoO3 (LSCO) layer was performed. The influence of the LaSrCoO3 buffer layer was analyzed taking advantage of the observed Raman spectral band variation, which varied according to different manufacturing procedures. In the presence of a LSCO layer, the A1(1TO) Raman mode, which was indicative of tetragonal distortion, was pronouncedly enhanced, and a slight deviation from the (0 0 1) plane of the film was observed from the angular dependence of the polarized Raman spectral intensity. Furthermore, the spectral band variation as well as the residual stress along the in-depth direction was measured in the film from cross-sectional spectral line scans. This latter measurement showed a relaxation of the lattice mismatch in the presence of LSCO and PbO layers. 相似文献
89.
Rajendra Kumar Singh 《Applied Surface Science》2009,255(15):6827-6831
Glasses with compositions 41CaO(52 − x)SiO24P2O5·xFe2O33Na2O (2 ≤ x ≤ 10 mol.%) were prepared by melt quenching method. Bioactivity of the different glass compositions was studied in vitro by treating them with simulated body fluid (SBF). The glasses treated for various time periods in SBF were evaluated by examining apatite formation on their surface using grazing incidence X-ray diffraction, Fourier transform infrared reflection spectroscopy, scanning electron microscopy and energy dispersive spectroscopy techniques. Increase in bioactivity with increasing iron oxide content was observed. The results have been used to understand the evolution of the apatite surface layer as a function of immersion time in SBF and glass composition. 相似文献
90.
Trivalent cerium-doped yttrium aluminum garnet (YAG:Ce3+) nanoparticles were successfully prepared by a facile sol–gel technique. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy were used to characterize the as-prepared phosphors. Well-crystallized fine nanoparticles were obtained at 1000 °C. Single-crystal nanoparticles with irregular shapes were obtained, with crystallite sizes ranging between 20 and 60 nm. PL intensity of the particles increased monotonically with decreasing Ce doping concentration and showed the maximum value at 0.1 at%. 相似文献