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  • 1
    Electronic Resource
    Electronic Resource
    Origin of picosecond-pulse-induced, degenerate four-wave-mixing signals in KTa1−xNbxO3 crystals (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 20-28 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transient gratings have been produced in KTa1−xNbxO3 by picosecond-pulse, two-photon excitation using degenerate four-wave-mixing techniques. The excitation process has been characterized through fluorescence studies, and the fluorescence is attributed to the transition between an excited state and the ground state of B4+ ions that are produced in ABO3 perovskite crystals. Strong electron-phonon coupling gives rise to the luminescence quenching. The observed degenerate four-wave-mixing signal is shown to be due predominantly to a phase grating caused by a change in the susceptibility associated with the formation of Nb4+ or Ta4+ ions in the peak region of the grating. The grating signal intensity was found to be dependent on the concentration of niobium ions and the crossing angle of the two laser write beams.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350312
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  • 2
    Electronic Resource
    Electronic Resource
    Study of epitaxial platinum thin films grown by metalorganic chemical vapor deposition (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 3735-3740 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The metalorganic chemical vapor deposition technique has been successfully applied to the growth of epitaxial platinum thin films on (100) surfaces of single-crystal potassium tantalate (KTaO3) and strontium titanate (SrTiO3). Platinum thin films grown on KTaO3 (100) at a rate of 70 nm/h showed strong Rutherford backscattering spectroscopy (RBS)/channeling effects with a χmin of 4%. In-plane φ and θ-2θ scan x-ray diffraction analysis demonstrated the three-dimensional epitaxial alignment of the platinum film with the KTaO3 substrate. Transmission electron micrographs viewed in cross section provided additional information regarding the nature of the epitaxial Pt-KTaO3 interface. The room-temperature resistivity of a 60-nm-thick Pt film on KTaO3 (100) was 12.0 μΩ cm. X-ray diffraction and pole-figure analysis showed that in the case of Pt films deposited on either fused quartz or Si (100) surfaces, the resulting films were polycrystalline and were fully textured with 〈111(approximately-greater-than) orientations perpendicular to the substrate surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352293
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  • 3
    Electronic Resource
    Electronic Resource
    Neutron study of crystal-field transitions in ErPO4 : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6069-6071 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The crystal-field splitting of the Er3+ ground multiplet 4I15/2 in ErPO4 is investigated by inelastic neutron scattering. Four excitations from the Γ7 ground state to the excited states and several transitions between the excited states have been identified. The observed transition energies and intensities are used to refine the parameters of the crystal-field potential. The calculated magnetic susceptibility χ(T) agrees well with experimental values from single-crystal measurements. A comparison of the neutron data with optical absorption and both nonresonance and resonance Raman scattering measurements has been made.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353472
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  • 4
    Electronic Resource
    Electronic Resource
    Ion-implanted optical waveguides in KTaO3 (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 49-52 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optical waveguides have been formed by helium-ion implantation in KTaO3. The implantation forms a confinement barrier near the projected range of the ion by decreasing the refractive index as much as 16% for ion doses of 4×1016 ions/cm2. This is the highest refractive-index change yet reported for ion-implanted crystalline planar waveguides. Guiding modes (with moderately low loss) are produced without the need for annealing out of color centers. During annealing studies, the index change reduces during an anneal stage near 400 °C, but waveguiding is maintained even after anneals to 900 °C. Loss measurements indicate a planar-waveguide loss of 〈1 dB/cm after a 400 °C anneal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350684
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  • 5
    Electronic Resource
    Electronic Resource
    Electron paramagnetic resonance investigations of divalent cobalt in single crystals of perovskite (CaTiO3) (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 5117-5118 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electron paramagnetic resonance (EPR) spectrum of Co2+ in CaTiO3 was observed at 9 GHz in the temperature range of 10–15 K. The results establish that Co2+ occupies four magnetically inequivalent sites in the orthorhombic CaTiO3 lattice. These sites become equivalent when the applied magnetic field is parallel to the so-called "pseudocubic'' b axis of the crystal. The magnetic axes in the plane perpendicular to the pseudocubic axis make an angle of ±28.5°±0.5° with the a and c axes of the host lattice. The site symmetry is qualitatively similar to that of the aliovalent ions Er3+ and Yb3+ in CaTiO3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457604
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  • 6
    Electronic Resource
    Electronic Resource
    Crystal-field excitations and magnetic properties of TmPO4 (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 4214-4222 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The magnetic-excitation spectrum of TmPO4 has been studied using inelastic neutron scattering techniques. Sharp crystal-field transitions were observed in spectra obtained at 15 and 100 K, yielding new information regarding the energy-level structure of the Tm3+ ground-multiplet splitting. The data were analyzed using a Hamiltonian that included the atomic free-ion and crystal-field interactions for an f12 configuration. Using the Tm free-ion parameters derived from optical spectroscopy of Tm3+ diluted in a LuPO4 host, a set of crystal-field parameters were obtained for Tm3+ in pure TmPO4. The calculated magnetic spectra of TmPO4 agree very well with the results of neutron and Raman measurements. The calculated bulk magnetic susceptibility of TmPO4 exhibits a large anisotropy at low temperature and is in good agreement with the experimental data. A significant contribution to the specific heat from the Tm3+ crystal-field states was found at temperatures below 100 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465028
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  • 7
    Electronic Resource
    Electronic Resource
    Hydrogen catalyzed crystallization of strontium titanate (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 2711-2718 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The crystallization rate of amorphous strontium titanate is enhanced by more than an order of magnitude during thermal annealing in water vapor as compared to a dry ambient. Time resolved optical reflectivity (TRR) has been combined with Rutherford backscattering spectrometry (RBS) and ion channelling to investigate this effect. Thin amorphous films (0.6 μm) were produced on single-crystal substrates of (100) strontium titanate by bombardment with 1.9 or 2.0 MeV Pb ions. Specimens were annealed under controlled ambient conditions (H2O, D2O, vacuum, 265–430 °C) and the solid phase epitaxial crystallization monitored in situ by TRR (633 nm). The TRR data were calibrated ex situ by transmission electron microscopy and RBS measurements. Isotope substitution, nuclear reaction analysis, and secondary-ion-mass spectrometry were utilized to reveal the uptake of hydrogen and oxygen into the implanted layer. Hydrogen is identified as the only species which penetrates to the crystal/amorphous interface. It is shown that the crystallization rate is proportional to the concentration of diffusing hydrogen (H or D) at the interface. The data show that the effect of water vapor, or more precisely, hydrogen, is to reduce the activation energy of crystallization from 2.1 to 1.0 eV. It is concluded that hydrogen, provided by the dissociation of water molecules at the surface, is a catalyst in the crystallization of amorphous strontium titanate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357574
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  • 8
    Electronic Resource
    Electronic Resource
    Stability of ion-implanted layers on MgO under ultrasonic cavitation (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 2781-2787 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of ion implantation and ultrasonic cavitation on the near-surface region of MgO single crystals were investigated. For 150 keV, room-temperature implantations of Ar+ or K+ at 5×1016–1017 ions cm−2 into a (100)-oriented surface of MgO, a dilatometric swelling of the implanted layer is observed perpendicular to the implanted surface. When these strained surface layers are then subjected to an ultrasonic (∼20 kHz) cavitation treatment, uniform layers (∼100–200 nm) can be removed from the MgO surface in a controlled manner. The thickness of the removed layer is directly related to the duration of the ultrasonic irradiation, but does not exceed the depth of the implanted species. When MgO implanted with Ar+ or Kr+ at fluences of 5×1016–1017 ions cm−2 is subsequently irradiated with 2 MeV He+ ions at 1016–1017 ions cm−2, the region exposed to the He+ beam is effectively "stabilized'' and is not removed by the ultrasonic treatment. K+ or Ar+ implantations at 〈5×1016 ions cm−2 produced no swelling of the layer, and subsequent ultrasonic irradiation with an energy flux of ∼120 W cm−2 did not remove the crystal surface as determined by profilometry. For MgO implanted with (approximately-greater-than)2×1017 ions cm−2, the implanted layer is highly strained and detaches from the underlying crystal without exposure to ultrasonic-cavitation effects. These findings are discussed in terms of the stressed states of the implanted layers, and their potential applications to the mechanical "etching'' of ceramics are considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363195
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  • 9
    Electronic Resource
    Electronic Resource
    Time-sliced Mössbauer absorption spectroscopy using synchrotron radiation and a resonant Bragg monochromator (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3686-3690 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Doppler absorption measurements have been used to investigate time-slice Mössbauer absorption spectroscopy for synchrotron radiation and a mosaic resonant Bragg monochromator. The energy widths for wide time intervals and the time-dependent narrowing of the spectral width of resonant Bragg scattering from a mosaic 57Fe2O3 crystal have been measured using a powdered 9.7 mg/cm2 57Fe2O3 absorber. The measurements are compared with calculations for a thick (9.7 mg/cm2) and a thin (0.5 mg/cm2) absorber, and the feasibility of high angular collimation neV range x-ray scattering spectroscopy using synchrotron radiation and time windowing is assessed. ©1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361199
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  • 10
    Electronic Resource
    Electronic Resource
    Annealing-environment effects in the epitaxial regrowth of ion-beam-amorphized layers on CaTiO3 (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 1519-1527 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of water-vapor ambients on the solid-state epitaxial regrowth of ion-beam-amorphized, near-surface layers on single-crystal CaTiO3 have been investigated using Rutherford backscattering-channeling spectroscopy, time-resolved reflectivity, and cross-sectional transmission electron microscopy (TEM). The presence of water vapor in the annealing atmosphere increases the thermally induced epitaxial regrowth rate and, within the temperature range studied (400–550 °C), decreases the activation energy for this process. TEM micrographs from samples which were partially regrown in high-H2O-concentration atmospheres revealed uneven amorphous/crystalline interfaces with fluctuations on the order of 5–10 nm. Samples annealed in water-vapor-deficient atmospheres exhibited very flat interfaces after partial epitaxial regrowth. The morphologies of these interfaces are explained in terms of a segregation of hydrogen ahead of the regrowth interface. Additionally, it has been determined that the absence of oxygen does not affect the regrowth rate. Samples annealed in oxygen concentrations as low as 10−21 atm exhibit growth rates that are identical to those measured for air-annealed CaTiO3 samples. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360244
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