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81.
Neodymium-substituted Bi4Ti3O12 (BNdT) thin films were prepared by a chemical solution deposition technique on platinum- coated silicon substrates. All of
the samples were annealed at the relatively low temperature of 600 °C by a rapid thermal annealing process in different atmospheres,
such as O2, air, and nitrogen, and vacuum. Irrespective of different annealing atmospheres, all of the BNdT thin films exhibit good
ferroelectric properties, such as a saturated hysteresis loop, good fatigue endurance, and low leakage current density. A
large remanent polarization (Pr) of ∼48 μC/cm2 with an electric field of 240 kV/cm was observed from the BNdT thin film annealed in O2 atmosphere. The BNdT thin films annealed in nitrogen and vacuum, at reduced oxygen partial pressures, exhibit smaller Pr than that annealed in oxygen. The difference of Pr of the BNdT thin films annealed in different atmospheres may originate from differences in the grain sizes and the number
of oxygen vacancies.
PACS 77.55.+f; 77.80.-e; 77.80.Fm; 81.15.-z 相似文献
82.
Thin Ca films were evaporated on Si(1 1 1) under UHV conditions and subsequently annealed in the temperature range 200–650 °C. The interdiffusion of Ca and Si was examined by ex situ Auger depth profiling. In situ monitoring of the Si 2p core-level shift by X-ray photoemission spectroscopy (XPS) was employed to study the silicide formation process. The formation temperature of CaSi2 films on Si(1 1 1) was found to be about 350 °C. Epitaxial growth takes place at T≥400 °C. The morphology of the films, measured by atomic force microscopy (AFM), was correlated with their crystallinity as analyzed by X-ray diffraction (XRD). According to measurements of temperature-dependent I–V characteristics and internal photoemission the Schottky-barrier height of CaSi2 on Si(1 1 1) amounts to qΦBn=0.25 eV on n-type and to qΦBp=0.82 eV on p-type silicon. 相似文献
83.
Many operators in Banach spaces occur as the integration operator of a suitable vector measure; their compactness is completely described in [19]. However, many important spaces X in analysis (and integration operators in such spaces) do not fall into this scheme because X is not normable. Characterizing the compactness of integration operators in this setting is the aim of this note. The methods and techniques employed are quite different to the Banach space arguments used in [19]. 相似文献
84.
W.-H. Chen 《Archiv der Mathematik》2002,79(5):396-400
Consider the class of closed Riemannian manifolds M of dimension dim(M) \geqq 3 \dim(M) \geqq 3 , Ricci curvature Ric(M) \geqq -(n - 1) \textrm{Ric}(M) \geqq -(n - 1) , diameter diam(M) < D and almost maximal volume. We show that the isomorphism types of fundamental groups characterize the diffeomorphism types of manifolds in such a class. In particular, it can be viewed as a generalization of the well-known Mostows rigidity theorem and a finiteness theorem. 相似文献
85.
Two methods for multi-element preconcentration from copper by reductive matrix precipitation are presented. In systematic investigations on the coprecipitation behaviour of Ag, Al, Au, Bi, Cd, Co, Cr, Fe, Ga, In, Mn, Mo, NJ, Pb, Sb, Se, Sn, Te and Zn during precipitation of the copper matrix as Cu2O or CuSCN, the separation parameters were optimized. By combination with a hexamethyleneammonium hexamethylenedithiocarbamate collector precipitation, a concentration of 8 elements (Cu2O precipitation) or 13 elements (CuSCN precipitation) in a small volume was achieved. The limits of detection of the procedures are, depending on the element, 0.1–5 μg g?1 for flame atomic absorption spectrometry (AAS) and 0.01–0.1 μg g?1 for graphite furnace AAS. The relative standard deviations are about 3%. The analytical performance of the procedures is compared with that of an electrolytic copper separation. 相似文献
86.
V. De Sabbata C. Sivaram H.-H. v. Borzeszkowski H.-J. Treder 《Annalen der Physik》1991,503(7):497-502
It is shown that in gravitational theories with torsion one is led to commutation rules corresponding to Landau-Peierls type uncertainty relations. 相似文献
87.
The finite-size corrections, central chargesc, and scaling dimensionsx of tricritical hard squares and critical hard hexagons are calculated analytically. This is achieved by solving the special functional equation or inversion identity satisfied by the commuting row transfer matrices of these lattice models at criticality. The results are expressed in terms of Rogers dilogarithms. For tricritical hard squares we obtainc=7/10,x=3/40, 1/5, 7/8, 6/5 and for hard hexagons we obtainc=4/5,x=2/15, 4/5, 17/15, 4/3, 9/5, in accord with the predictions of conformal and modular invariance. 相似文献
88.
I. L. Davies K. E. Markides M. L. Lee M. W. Raynor K. D. Bartle 《Journal of separation science》1989,12(4):193-207
Although coupled liquid chromatographygas chromatography (LC-GC) was first demonstrated ten years ago, only in the last few years has there been a sudden surge of interest in the technique. Approximately 70% of the total number of LC-GC applications have been published in the last two years (1987–88) alone. This review categorizes LC-GC publications into four main application areas: fossil fuels, foods, environmental samples, biologiical/pharmaceutical samples, and miscellaneous samples. Multidimensional separations carried out using other coupled-column chromatographic techniques (such as supercritical fluid chromatography (SFC) with GC, and on-line trace enrichment-GC) have also been included in this review. 相似文献
89.
90.
Summary In 1980 Dahmen-DeVore-Scherer introduced a modulus of continuity which turns out to reflect invariance properties of compound cubature rules effectively. Accordingly, sharp error bounds are derived, the existence of relevant counterexamples being a consequence of a quantitative resonance principle, established previously. 相似文献