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  • 1
    Electronic Resource
    Electronic Resource
    Nanocages of layered BN: Super-high-pressure nanocells for formation of solid nitrogen (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 8523-8532 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We observed high N contents inside BN fullerenelike multilayered nanocages (ca. 30–100 nm) formed by reacting CNx nanotubes (x≤0.1) and B2O3 in a N2 atmosphere at 1985–2113 K. High-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy, energy dispersion x-ray spectroscopy, electron diffraction analysis, spatially resolved energy-filtered TEM, and in situ TEM electron irradiation studies suggest that super-high pressures (of several GPa) are generated inside nanocages, responsible of crystallizing gaseous nitrogen trapped within the BN shells. In addition, high-pressure-induced phase transformation of graphiticlike BN into diamondlike cubic BN occurs inside the nanocages. Thus, BN nanocages play an unusual role of super-high-pressure nanocells. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1469599
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  • 2
    Electronic Resource
    Electronic Resource
    London penetration depth of superconductors having lifetime broadened density of states (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 332-333 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: London penetration depth λL was calculated for superconductors having lifetime broadened density of states. With the increase of gap states, λL increases and the temperature dependence deviates from the ordinary form. The model gives a T2 dependence of λL in the case of weak-coupling limit of the Bardeen–Cooper–Schrieffer theory. The results are discussed referring to some experimental results of magnetic field penetration depth of oxide superconductors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99908
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  • 3
    Electronic Resource
    Electronic Resource
    Epitaxial growth of YBa2Cu3O7−x thin films on (110) SrTiO3 single crystals by activated reactive evaporation (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 2232-2234 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The orientation of YBa2Cu3O7−x thin films grown on (110) planes of SrTiO3 by activated reactive evaporation was investigated by means of reflection high-energy electron diffraction. The orientation of the films depended on the substrate temperature. The films with (110) planes parallel to the substrate surface grew in a narrow range of substrate temperatures around 530 °C, while the films with (103) planes parallel to the surface grew at temperatures above 600 °C. The change of the epitaxial orientation with the substrate temperature is discussed in terms of the temperature dependence of the lattice mismatch between YBa2Cu3O7−x and SrTiO3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100511
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  • 4
    Electronic Resource
    Electronic Resource
    Preparation and characterization of (111)-oriented Fe3O4 films deposited on sapphire (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 3168-3172 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Films of various iron oxides including FeO, Fe3 O4 , and α-Fe2 O3 were formed on the α-Al2 O3 (0001) surface by a reactive vapor deposition method and characterized by x-ray diffraction and conversion electron Mössbauer spectroscopy (CEMS). The formation range for each phase was determined as a function of the substrate temperature (Ts ) and oxygen partial pressure (PO2 ). Typically, the deposition of (111)-oriented epitaxial magnetite films could be performed at low temperatures of Ts =523∼623 K and PO2 =1.0–5.0×10−4 Torr. Good stoichiometry of the as-grown films were confirmed by CEMS, and the Verwey transition was clearly detected by measurements of resistivity and CEMS down to 77 K. However, the large lattice mismatch between the substrate and Fe3 O4 resulted in a columnar particle growth. The initially grown phase on such a mismatched substrate was specifically characterized by depositing the Mössbauer active isotope, 57 Fe, only at the deepest layers. On the other hand, by depositing 57 Fe only in the topmost layers, surface layers of well-crystallized films have been found to be rather stable against oxidation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344154
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  • 5
    Electronic Resource
    Electronic Resource
    Valence evaluation of cerium ions in Ce-doped α-sialon by electron energy loss spectra (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 5469-5472 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: For a long time cerium ions, both Ce3+ and Ce4+, have not been considered to be able to enter the interstitial sites in an α-sialon structure until recent successes in the preparation of cerium-doped α-sialon materials using CeO2 as the starting powder. It is then of great importance and necessity to know the chemical valence of these incorporated cerium ions. Meanwhile, the specific structure of the interstices in α-sialon provides quite a different chemical environment upon which the electronic structures of cerium ions could be different from those ever reported in, for instance, metallic compounds and oxides. Electron energy loss spectra (EELS) in the M-edge region of rare-earth elements carries information on the initial state 4f occupancy. We have acquired and examined the M4,5-edge spectra of cerium at different locations in the microstructure. It has been found that all the Ce(IV) ions in the intergranular glass and the majority inside the α-sialon crystals have been reduced to Ce(III) while there exist inside the crystal cerium ions showing 4f0 initial-state peaks on the EELS spectrum. The 4f0 peak locates at about 0.6 eV higher in energy than that for CeO2. An increased and possibly by far the highest weight of f0 state is derived for Ce(IV) ions in α-sialon. The spectral evidences confirm the general suggestion of the unstability of Ce(IV) ions with silicon nitride. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1365433
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  • 6
    Electronic Resource
    Electronic Resource
    High-resolution transmission electron microscopy of cubic Si3N4 (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 3070-3072 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A cubic Si3N4 phase/nanostructure has been characterized by means of high-resolution analytical electron microscopy. The specimen prepared from β-Si3N4 powders at a high pressure and temperature by shock wave compression contained nanometer-sized Si3N4 crystallites. The results of nano-beam electron diffraction analysis and high-resolution lattice images as well as computer simulations revealed that the Si3N4 crystallites had a cubic symmetry with spinel structure. The electron energy loss spectrum suggested that the chemical compositions of these nanostructures were close to Si3N4. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1287765
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  • 7
    Electronic Resource
    Electronic Resource
    Preparation and structural analysis of a PbSe-SnSe strained-layer superlattice (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 206-214 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new superlattice composed of semiconducting PbSe and SnSe has been grown epitaxially on cleaved NaCl substrates by the vapor deposition method. The samples were characterized by x-ray diffraction and cross-sectional high-resolution transmission electron microscopy. Two materials have different crystal structures; PbSe has the cubic NaCl-type structure, whereas SnSe has the orthorhombic SnS-type structure, which is a distorted NaCl-type structure. The lattice mismatch between them is quite large, about 3%, and their growth planes have different symmetries. Therefore, this superlattice should not be classified as an ordinary superlattice like the GaAs-AlAs system, but as a so-called strained-layer superlattice. As a result of the structural analyses, it has been found that the samples have an ideal structure whose compositional modulation can be described by the step model with no mixed layers at the interface. In addition, we have observed a change of crystal symmetry in the PbSe layers: PbSe adopts the SnS-type structure when the thickness is less than about 30 A(ring), for coherency strain, but it relaxes back to the NaCl-type structure, with loss of the coherency, when the thickness is larger.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338857
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  • 8
    Electronic Resource
    Electronic Resource
    Si3N4/SiC interface structure in SiC-nanocrystal-embedded α-Si3N4 nanorods (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1515-1519 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Si3N4/SiC interface structure in SiC-nanocrystal-embedded α-Si3N4 nanorods was studied by high-resolution transmission electron microscopy. The SiC-nanocrystal-embedded α-Si3N4 nanorods were synthesized by the method of carbothermal reduction of SiO in pure N2 atmosphere, while the SiC nanocrystals were produced from a substitution of SiC for Si3N4. Between SiC and Si3N4, there are three kinds of plane configurations and a set of orientation relationships, i.e., [11¯0]SiC//[0001]Si3N4 and nearly (111)SiC//(101¯0)Si3N4 with low-angle discrepancy of either 3° or 5°. The origin of the low-angle discrepancies was explained in terms of a reciprocal lattice theory for heteroepitaxial interfaces. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1428106
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  • 9
    Electronic Resource
    Electronic Resource
    Nanobelts of the dielectric material Ge3N4 (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 4565-4567 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ge3N4 nanobelts 30–300 nm in width were synthesized by thermal reduction of a mixed Ge+SiO2 powder in NH3 atmosphere. These nanobelts were studied by high-resolution transmission electron microscope equipped with an x-ray energy dispersive spectrometer. In these synthesized nanobelts, the existence of α and β phases of Ge3N4 was identified. The α phase exhibiting slight difference from an ideal α-Ge3N4 phase was also found in the present Ge3N4 material. The mechanism of formation of the Ge3N4 nanobelts is discussed. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1428634
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  • 10
    Electronic Resource
    Electronic Resource
    Insights into the structure of BN nanotubes (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 1979-1981 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The following features of multiwalled BN nanotubes were discovered using a field emission high-resolution analytical transmission electron microscope: (i) coexistence of hexagonal and rhombohedral stacking in nanotube shell assembly; (ii) flattening of nanotube cross section, which makes possible clear atomic resolution of the core structure in a three-shelled nanotube; and (iii) change in chirality of tubular layers from armchair to zigzag arrangement in a 30° double-walled nanotube kink, as revealed by atomically resolved images of tube wall segments. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1313251
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