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排序方式: 共有605条查询结果,搜索用时 218 毫秒
41.
Oleksandr Romanenko Petr Slepička Petr Malinsky Mariapompea Cutroneo Vladimír Havránek James Stammers Václav Švorčík Anna Macková 《Surface and interface analysis : SIA》2020,52(12):1040-1044
3D microstructures in pure poly(dimethylsiloxane) (PDMS) and PDMS with embedded Au nanoparticles were prepared by ion beam lithography without any further etching. Two mega-electron volts helium and 10 MeV oxygen ions were used for ion microstructuring. Parallel lines of 1 mm in length and 10 μm in thickness were fabricated for investigation of the effect of the nanoparticles presence in the polymer on the surface morphology of the created microstructures. The created microstructures were checked by optical microscope. Infrared (IR) spectrometry was used to study the effect of the ions type and fluence on the chemical changes of the material. Atomic force microscopy was used for the fine detail study as well as for checking the microstructure quality. Analysis revealed an increased radiation resistance of the nanocomposite compared to the pure PDMS. Shrinkage is proportional to the fluence, but the maximum value for both materials is limited by saturation. 3D microstructure in modified PDMS obtained at the same irradiation condition as pure PDMS is characterized by its smaller height. Obtaining the microstructure in nanocomposite of the same height as in pure PDMS by increasing the fluence can be impossible due to saturation of shrinkage and/or radiation-induced heating of the material. 相似文献
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Derivatives of Tr?ger's base (TB) have played important roles in receptor construction due to their rigid V-shape. A new class of these compounds are the oligo-TBs, which can function as cavitands. Herein, we describe both stepwise and one-step (oligomerization) methods suitable for the preparation of linear oligo-TBs. 相似文献
46.
Using tools of quantum information theory we show that the ground state of the Dicke model exhibits an infinite sequence of instabilities (quantum-phase-like transitions). These transitions are characterized by abrupt changes of the bi-partite entanglement between atoms at critical values kappa(j) of the atom-field coupling parameter kappa and are accompanied by discontinuities of the first derivative of the energy of the ground state. We show that in a weak-coupling limit (kappa1 < or = kappa < or = kappa2) the Coffman-Kundu-Wootters inequalities are saturated, which proves that for these values of the coupling no intrinsic multipartite entanglement (neither among the atoms nor between the atoms and the field) is generated by the atom-field interaction. We show that in the strong-coupling limit the entangling interaction with atoms leads to a highly sub-Poissonian photon statistics of the field mode. 相似文献
47.
Fernando?León-SaavedraEmail author Vladimír?Müller 《Integral Equations and Operator Theory》2004,50(3):385-391
Let T B(X) be a hypercyclic operator and a complex number of modulus 1. Then T is hypercyclic and has the same set of hypercyclic vectors as T. A version of this results gives for a wide class of supercyclic operators that x X is supercyclic for T if and only if the set {tTn x : t > 0, n = 0, 1, ...} is dense in X. This gives answers to several questions studied in the literature. 相似文献
48.
The iron silicides samples were prepared by annealing of iron films evaporated onto silicon wafers and capped with amorphous silicon thin overlayers. Semiconducting FeSi2 phase is formed by annealing at the temperatures from 550°C to 850°C. The optical properties of the FeSi2 layers have been deduced from reflectance and transmittance measurements carried out in the temperature range of (77–380) K. The spectral dependence of the absorption coefficient favours direct allowed transitions with forbidden energy gap of 0.87eV at the room temperature. The application of a simple three-parameter semiempirical formula to the temperature dependence of the direct energy gaps leads to the following best fit parameters: the band gap at zero temperature E
g (0) = (0.895 ± 0.004)eV, the dimensionless coupling parameter S = 2.0 ± 0.3, and the average phonon energy <hw> = (46 ± 8)meV. By examining all the reported triplets of parameters for -FeSi2 fabricated by different techniques and thermal processes, an obvious discrepancy can be found for the lattice coupling parameter and average phonon energy, although the bandgaps at 0 K are very similar. Unlike the theoretical prediction and the earlier reported result, our results do not show any evidence of a particularly strong electron-phonon interaction, which would give the lower carrier mobilities. -FeSi2 seems to be an intriguing material where states with energies near the band edges permit ambiguous interpretation of the character of transitions. From optical model for the thin film-substrate system we found the index of refraction to be (5–5.9) in the photon energy interval from 0.65 to 1.15eV. There is also indication of an additional higher-energy absorption edge at l.05eV. 相似文献
49.
Zuzana Matkovičová Vladimír Štrbík Gustav Plesch Michaela Valeriánová Agáta Dujavová 《Central European Journal of Physics》2007,5(3):398-404
Superconducting Tl-based films were prepared on a LaAlO3 single crystal substrate. Spray pyrolysis of Ba, Ca and Cu nitrate solutions was used for deposition of the precursor films.
They were subsequently ex-situ thallinated in flowing oxygen (open system). While the superconducting Tl-2212 phase formed at an annealing temperature
of 880°C, thallination at 900°C led to the formation of a Tl-2223 /Tl-2212 mixture. The amount of Tl-2223 increased with prolonged
thallination, whereas the Tl-2212 phase progressively disappeared. Films prepared in such a manner were c-oriented and contained only low amounts of non-superconducting impurities. The resulting samples were characterized by XRD
and SEM and their T
C
values were determined by resistive four-point measurements. They showed critical temperatures in the range of T
ON
= 125–135 K, T
C0 = 91–93 K. Differences between the composition and properties of the obtained films and those thallinated in closed systems
under 50 kPa of oxygen are discussed in this paper. Results show that the Tl-2212 → Tl-2223 transformation proceeds at a slower
rate under flowing oxygen than in a closed system.
Presented at 5-th International Conference Solid State Surfaces and Interfaces, November 19–24, 2006, Smolenice Castle, Slovakia. 相似文献
50.
Václav Štengl Snejana Bakardjieva Natalie Murafa Eva Večerníková Jan Šubrt Vladimír Balek 《Journal of nanoparticle research》2007,9(3):455-470
A new method for preparation of titania nanowires with diameter around 10 nm and length up to 2–3 μm is described. The precursor
was prepared from sodium titanate by adding ethylene glycole (EG) and heating at temperature of 198°C for 6 h under reflux.
The sodium titanate glycolate formed by this way aggregated into 1D nanostructures and was subsequently transformed into titania
glycolate during a chemical treatment with 98% sulfuric acid. Titania nanowires with variable amount of anatase and rutile
were prepared by heating to temperatures in the range 350–1000°C. The precursor as well as titania based samples were characterized
by X-ray diffraction, Infrared spectroscopy, Scanning electron microscopy, High resolution transmission microscopy, Thermogravimetry,
Differential thermal analysis, Evolved gas analysis and Emanation thermal analysis. The nitrogen adsorption/desorption was
used for surface area and porosity determination. The photoactivity of the prepared titania samples was assessed by the photocatalytic
decomposition of 4-chlorophenol in an aqueous slurry under UV irradiation of 365 nm wavelength. 相似文献