Materials Literature
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The emission properties of a new phosphor based on LiTaO3:Tb3+ are described. It is shown to be a storage phosphor, i.e., after previous x-ray exposure, Tb3+ emission in green-red region of spectrum can be photostimulated by light in 400–800 nm spectral range. Emission centers (Tb3+ ions), electron storage centers (ox…
Drops of molten silicon surrounded by a SiO2–BaO–CaO flux were undercooled at 350 K below their melting temperature. This undercooling is 75 K greater than the largest one reported so far for bulk silicon. To account for this result as well as the nucleation data from laser-melted thin films, classical nucleation theo…
It is shown that the low frequency collective modes of quasilinear polymers can contribute to the vibrational polarizability and hyperpolarizability despite the fact that their infrared or Raman intensity vanishes in the infinite chain limit. The most significant of these modes are characterized and the dynamic vibrat…
We report temperature-dependent redistribution of spectral weight in photoemission spectra of ${\mathrm{La}}_{0.6}$${\mathrm{Sr}}_{0.4}$${\mathrm{MnO}}_{3}$ over a wide energy range of several eV. We attribute this to a change in the electron correlation strength induced by the changing degree of ferromagnetic order w…
In this study we present photoemission data for three different types of amorphous carbon modifications (a-C:H, ta-C:H, and ta-C) that owe their properties to their different preparations by radio frequency plasma, plasma beam, or arc discharge. Their properties are investigated by means of their characteristic plasmo…
Using synchrotron radiation, we have performed a high-resolution X-ray diffraction study of a phase transition between the incommensurate phase and the commensurate phase characterized by the wave vector q =3 c * /7 in [N(CH 3 ) 4 ] 2 MnCl 4 under pressure. The pressure dependence of the wave vector q exhibits an “inc…
The structural saturation and stability, the energy gap, and the density of states of a series of small, silicon-based clusters have been studied by means of the PM3 and some ab initio (HF/6-${31\mathrm{G}}^{\mathrm{*}}$ and 6-311++${\mathrm{G}}^{\mathrm{*}\mathrm{*}}$, CIS/6-${31\mathrm{G}}^{\mathrm{*}}$ and MP2/6-${…
The magnetic properties of a series of Ce2Fe17−xAlx solid solutions with x equal to 0.00, 0.88, 2.06, 2.81, 3.98, 5.15, 6.08, 7.21, 8.20, 9.08, 9.84, and 10.62 have been studied by magnetic measurements, neutron diffraction, and Mössbauer spectroscopy. The compounds crystallize in the rhombohedral Th2Zn17-type structu…
The optical absorptions of anodically etched p+ and n+ porous silicon (PS) films were investigated by photothermal deflection spectroscopy. Si–H stretching overtones and combination bands of Si–F and Si–H were observed. The defect model in hydrogenated amorphous silicon was used to explain the Urbach edge and the subg…
In the literature a relation is often used that correlates Debye temperature and bulk modulus by a square-root law. It was recently shown that, for different cubic crystal structures, such a law is only fulfilled within relatively large error limits. If one takes, however, the average of the elastic constants of the t…
A wet thermal oxidation method is proposed to passivate the electrochemically etched porous silicon. Bright and stable photoluminescence is achieved by wet oxidation at relatively low temperatures of 400–500 °C. The Fourier transform infrared absorption shows that the formation of SiH(O3), SiH(SiO2), SiH2(O2) bonds ma…
In a comparative study we calculated the spin and orbital moments, spin and charge densities, and 4f crystal field (CF) parameters of the rare-earth transition-metal intermetallics ${\mathrm{Sm}}_{2}$${\mathrm{Fe}}_{17}$, ${\mathrm{Sm}}_{2}$${\mathrm{Fe}}_{17}$${\mathit{Z}}_{3}$ (Z=C,N), and ${\mathrm{Sm}}_{2}$${\math…
The aging characteristics of the electrostrictive lead magnesium niobate–lead titanate [(1−x)PMN–xPT] under dc bias field were investigated. It was observed that the amount of aging increases with the PT content for the compositions investigated (x≤0.3). For a fixed composition, the aging rate rises with temperature.…
The multiband envelope-function formalism---of which a convenient, analytical formulation is presented---is used to investigate the energies and wave functions of valence-band levels in spherical nanocrystallites of several III-V and II-VI compound semiconductors with finite spin-orbit splitting energy \ensuremath{\De…
Optical processes at the absorption edge in Y-doped BaCeO3 films with thicknesses of 160 and 4600 nm have been studied in the temperature region between 20 and 1000 °C. For the first time, optical band-gap energies of Y-doped BaCeO3 were determined with a room temperature value of 4.1 eV and a temperature coefficient…
Strong negative-electron-affinity effects have been observed on the surface of as-grown chemical-vapor-deposited diamond using secondary-electron emission. The samples were randomly oriented polycrystalline diamond films terminated with hydrogen. The effect appears as an intensive peak in the low-energy part of the sp…
A Kohn-Sham (KS) scheme for solids treating exchange exactly is introduced. The scheme emerges from a recently introduced exact formal KS procedure [A. G\"orling and M. Levy, Phys. Rev. A 50, 196 (1994)]. The exact density-functional exchange potential is obtained in terms of its Fourier components. The method can eas…
Mn-activated Zn2SiO4 and Ce-activated Y2SiO5 multilayer thin film electroluminescent (EL) devices were prepared by rf magnetron sputtering. The EL response of the devices under different voltages, frequencies, and pulse widths, as well as the transferred charge and decay characteristics were studied. The EL device usi…
We study the electronic structure of copper oxide clusters, ${\mathrm{Cu}}_{2}$${\mathrm{O}}_{\mathit{x}}$ (x=1--4), using anion photoelectron spectroscopy and density-functional calculations. The experiment is used to successfully guide a computational search for the cluster geometries. The predicted electron affinit…
The electronic structures of the itinerant ferromagnets ${\mathrm{Cr}}_{1\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$Te (\ensuremath{\delta}=0.05, 0.25, and 0.375) have been studied by photoemission spectroscopy. The valence-band spectra are compared with the density of states given by band-structure calculat…