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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
    Atomic layer growth of oxide thin films with perovskite-type structure by reactive evaporation (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 2840-2845 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial growth of BaTiO3 and SrTiO3 films by the reactive evaporation method was investigated using reflection high-energy electron diffraction (RHEED). The investigations were carried out using two growth methods: coevaporation and alternate evaporation of the metal elements in an oxygen atmosphere. Atomic layer growth was achieved by the alternate supply of Ba or Sr and Ti on the growing surface. In the case of coevaporation, epitaxial growth occurred in a two-dimensional unit-cell-by-unit-cell mode. The surface of each unit cell is terminated by a (TiO2) layer. Artificial superlattices of BaTiO3/SrTiO3 were fabricated by monitoring the film thickness with the RHEED oscillations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351536
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  • 3
    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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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    Erratum: Epitaxial growth and dielectric properties of BaTiO3 films on Pt electrodes by reactive evaporation [J. Appl. Phys. 76, 7833 (1994)] (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 6073-6073 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359616
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  • 6
    Electronic Resource
    Electronic Resource
    Epitaxial growth and dielectric properties of BaTiO3 films on Pt electrodes by reactive evaporation (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 7833-7838 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin films of BaTiO3 have been epitaxially grown on Pt(001)/MgO(100) substrates by reactive evaporation. Structural and electrical properties were investigated as a function of film thickness. In situ reflection high-energy electron diffraction and cross-sectional transmission electron microscope observations have revealed that the BaTiO3 films are epitaxially grown on Pt/MgO substrates from the initial stage without any other phase formation. From the images of an atomic force microscope, it has been found that islands of BaTiO3 are present on the bare Pt surface at the initial stage of deposition; the island structure changes to a continuous layer above 1.2 nm in thickness and BaTiO3 grows in a two-dimensional mode. The lattice parameters and the dielectric properties are dependent on the film thickness. Thermodynamic theory was introduced to explain the thickness dependence of the relative dielectric constant εr. Good agreement between the experimental results and the theoretical calculations leads to the conclusion that the thickness dependencies of the lattice parameters and the dielectric constants are caused by the two-dimensional stress due to the lattice mismatch between Pt and BaTiO3 and/or the difference in the thermal expansion coefficients of BaTiO3 and the MgO substrate. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357891
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  • 7
    Electronic Resource
    Electronic Resource
    Anomalous misfit strain relaxation in ultrathin YBa2Cu3O7−δ epitaxial films (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 3653-3662 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultrathin YBa2Cu3O7−δ epitaxial films were successfully grown in situ on (001) SrTiO3 and MgO substrates by means of ozone-incorporating activated reactive evaporation. The x-ray-diffraction study was carefully examined to determine the structural properties of the grown films. Excellent crystallinity with no interfacial disorders was revealed by the appearance of the Laue oscillations. It was found that in a well lattice-matched YBa2Cu3O7−δ/SrTiO3 system, the crystallinity was deteriorated due to defect introduction at the critical layer thickness hc ( ∼ 130 A(ring)). Interestingly, also in a poorly lattice-matched YBa2Cu3O7−δ/MgO system, excellent crystallinity was revealed even at above hc ( 〈 24 A(ring)). This implies that an anomalous misfit relaxation process exists in the YBa2Cu3O7−δ/MgO system. In such a system, no crystal imperfection of the MgO substrate caused by defect introduction was elucidated by the grazing incidence x-ray scattering, which indicated that the MgO substrate did not contribute to the anomalous misfit relaxation. The anomalous growth manner was also found in YBa2Cu3O7−δ/MgO according to surface morphology investigations. Below 40 A(ring)( (approximately-greater-than) hc), island nucleation growth was found. Above 40 A(ring), it was observed that an atomically smooth surface was obtained and the crystallinity was simultaneously improved. It is suggested that YBa2Cu3O7−δ possesses an anomalous misfit relaxation mechanism, and that especially in the growth on MgO, it couples with the characteristic growth behavior at the initial stage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348513
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  • 8
    Electronic Resource
    Electronic Resource
    Depth selective Mössbauer spectroscopic study of Fe3O4 epitaxial films (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 1735-1740 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Several (111) oriented 56Fe3O4 films containing a 5-A(ring)-thick 57Fe3O4 probe layer at or below the surface were grown epitaxially on the α-Al2O3 (0001) surface by a reactive vapor deposition method. Conversion electron Mössbauer spectroscopy was applied at 6, 78, and 300 K by using a recently developed helium-filled proportional counter. The well-crystallized surface has been found to be surprisingly stable even in air as characterized by the Mössbauer parameters that are almost the same as for the bulk. Moreover, the Verwey transition was detected clearly even in the 5-A(ring)-thick surface layer. However, the ferrous components seem to have changed their Mössbauer parameters probably because of their sensitivity to any crystalline field modifications in the surface. Generally speaking, the quality of epitaxial Fe3O4 films is very high: Any unusual surface state, if present, is confined in a shallow depth of ≤ 5 A(ring).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346602
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  • 9
    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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  • 10
    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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