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  • 1
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    Softening of infrared-active mode of perovskite BaZrO3 proved by terahertz time-domain spectroscopy (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-05-07
    Description: The low-frequency infrared-active optical modes were studied in a barium zirconate, BaZrO 3 , single crystal with the perovskite structure using terahertz (THz) time-domain spectroscopy (TDS). The real and imaginary parts of the dielectric constants were accurately determined in the frequency range between 0.2 and 2.7 THz. Upon cooling from room temperature to 8 K, the lowest-frequency TO1 mode at 2.32 THz showed a pronounced softening to 1.94 THz. The real part of the dielectric constant at 0.5 THz determined by THz-TDS obeys Barrett's relation, and the existence of a plateau confirms that the quantum effects lead to saturation of the soft mode frequencies of the TO1 and TO2 modes below ≈20 K. This is reminiscent of incipient ferroelectrics with the perovskite structure such as CaTiO 3 .
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 2
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    Structural analysis of polymer thin films using GISAXS in the tender X-ray region: Concept and design of GISAXS experiments using the tender X-ray energy at BL-15A2 at the Photon Factory (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-09-02
    Description: If small angle X-ray scattering (SAXS) utilizing the soft X-ray region is available, advanced and unique experiments, which differ from traditional SAXS methods, can be realized. For example, grazing-incidence small angle X-ray scattering (GISAXS) using hard X-ray is a powerful tool for understanding the nanostructure in both vertical and lateral directions of thin films, while GISAXS utilizing the tender X-ray region (SX-GISAXS) enables depth-resolved analysis as well as a standard GISAXS analysis in thin films. Thus, at BL-15A2 at the Photon Factory, a dedicated diffractometer for SX-GISAXS (above 2.1 keV) was constructed. This diffractometer is composed of four vacuum chambers and can be converted into the vacuum state from the sample chamber in front of the detector surface. Diffractions are clearly observed until 12th peak when measuring collagen by SAXS with an X-ray energy of 2.40 keV and a camera length of 825 mm. Additionally, we conducted the model experiment using SX-GISAXS with an X-ray energy of 2.40 keV to confirm that a poly(methyl methacrylate)-poly( n -butyl acrylate) block copolymer thin film has a microphase-separated structure in the thin film, which is composed of lamellae aligned both parallel and perpendicular to the substrate surface. Similarly, in a polystyrene-poly(methyl methacrylate) block copolymer thin film, SX-GISAXS with 3.60 keV and 5.73 keV revealed that hexagonally packed cylinders are aligned parallel to the substrate surface. The incident angle dependence of the first order peak position of the q z direction obtained from experiments at various incident X-ray energies agrees very well with the theoretical one calculated from the distorted wave Born approximation.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 3
    Electronic Resource
    Electronic Resource
    Reactions of highly excited oxygen atoms O(2p33s,5S) with simple gas molecules (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 9094-9098 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electron pulse irradiation of 10 atm He containing one of CO, CO2, NO, NO2, or N2O at small amounts produced highly excited oxygen atoms O(2p33s,5S), which subsequently disappeared by their reactions with parent molecules. The rate constants have been determined from the absorption decay curves at 777.3 nm O(2p33p,5P)←O(2p33s,5S). The rate constants for the reactions of O(2p33s,5S) with Xe, H2, N2, CH4, and C2H6 could be determined in the irradiation of mixtures of He, O2, and these gases with electron pulses. The upper limit of a quenching rate constant was estimated for Kr. The observed rate constants showed good correlation with the quenching rate constants of Kr(4p55s,3P2) or Xe(5p56s,3P2) by the same gas molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463336
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  • 4
    Electronic Resource
    Electronic Resource
    11B and 10B magic-angle spinning nuclear magnetic resonance studies of cubic boron nitride films prepared by plasma chemical vapor deposition (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 1734-1737 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 11B and 10B magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy was conducted to characterize cubic boron nitride films prepared by plasma chemical vapor deposition. Similarities and differences between cubic boron nitride films and polycrystals synthesized at high pressure and high temperature were clarified by chemical shift and linewidth. The same local structure and tetrahedral symmetry of boron atoms in both forms was demonstrated, and a higher defective density appeared to exist in the film form, agreeing well with results from Raman measurements. Noncubic-phase impurities, i.e., amorphous, turbostratic, and hexagonal phases, in films were also detected in 11B MAS NMR spectra, and the possibility of removing these impurities by chemical etching was demonstrated. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1338516
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  • 5
    Electronic Resource
    Electronic Resource
    Transmission electron microscopy study of B-site cation configurations in perovskite-structured Pb(Mg1/2W1/2)O3-Pb(Ni1/3Nb2/3)O3-PbTiO3 ceramics (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 4144-4151 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Configurations of B-site cations in the perovskite-structured ternary system Pb(Mg1/2W1/2)O3-Pb(Ni1/3Nb2/3)O3-PbTiO3 (PMW-PNN-PT) of interest for multilayer ceramic capacitors were studied by transmission electron microscopy. The evaluated specimens were four PMW/PNN/PT compositions: 10/30/60, 30/30/40, 50/30/20, and 70/30/0 on a compositional line with 30 mol % PNN content. A "core-shell-type'' microstructure was seen in the 10/30/60 specimen composition, which has a "normal'' ferroelectric characteristic, along with typical ferroelectric domain structures. The B-site cation ordering in the 10/30/60 composition was not detectable in the selected-area electron diffraction pattern. On the other hand, an "island-type'' microstructure, consisting of clusters (∼1–2 nm) with B-site cations 1:1 ordered, was observed in the 30/30/40, 50/30/20, and 70/30/0 compositions, which have relaxor-type characteristics. In the 70/30/0 composition, larger stripe-shaped ordered regions (∼20–200 nm) were also observed. These ordered regions extended from the center of the grain to the boundary. On the basis of the results obtained, origins of the dielectric behaviors for this system, that is, a "normal'' ferroelectric, a relaxor ferroelectric, and an antiferroelectric, were discussed from the point of view of the B-site cation configurations. The PMW component plays two roles in this ternary system, corresponding to its content. When the PMW content is low, Mg and W ions are disordered in the B-site sublattice, and interrupt the ferroelectricity. With increasing PMW content, small ordered clusters (∼1–2 nm) are formed, which are believed to localize superparaelectric potentials effectively and dominate a degree of a diffuse phase transition in the solid-solution system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355996
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  • 6
    Electronic Resource
    Electronic Resource
    Competition between fundamental and second-harmonic operations in a submillimeter wave gyrotron (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1594-1596 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Competition between electron cyclotron fundamental (f=fc) and second-harmonic (f=2fc) operation in a submillimeter wave gyrotron is described. Even when the magnetic field intensity is adjusted to the optimum value for second-harmonic operation, we can get a pure mode only for small beam currents. As the beam current is increased, excitation of the fundamental appears and eventually suppresses the second harmonic. The observed competition between the fundamental and second harmonic is compared with a computer simulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105135
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  • 7
    Electronic Resource
    Electronic Resource
    Schottky barriers and contact resistances on p-type GaN (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 3537-3539 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We measured the Schottky barrier heights and specific contact resistivities of four different metals on p-type GaN. The Schottky barrier heights of Pt, Ni, Au, and Ti were obtained from the current-voltage characteristics to be 0.50, 0.50, 0.57, and 0.65 eV, respectively. The specific contact resistivities were 0.013, 0.015, 0.026, and 0.035 Ω⋅cm2, respectively. Our experimental results proved that the Schottky barrier heights and specific contact resistivities decrease with increase in metal work function as expected theoretically. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117237
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  • 8
    Electronic Resource
    Electronic Resource
    Development of a second cyclotron harmonic gyrotron operating at 0.8 mm wavelength (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 1743-1745 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This letter describes the development of a submillimeter wave gyrotron operating at the second harmonic of the cyclotron frequency. The observed frequency is 383 GHz, which corresponds to the wavelength of 0.79 mm, and the output power is about 1 kW. We believe that the frequency is a world record for a stable, long pulse gyrotron operation at the second cyclotron harmonic, without a competition with the operation at the fundamental. Comparisons with the simulation results are represented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103086
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  • 9
    Electronic Resource
    Electronic Resource
    Carrier transport property in the amorphous silicon/amorphous silicon carbide multilayer studied by the transient grating technique (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 1259-1261 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The in-plane diffusion coefficient and lifetime of photogenerated carriers in amorphous silicon have been measured by the transient grating technique in amorphous silicon (a-Si)/silicon carbide (a-SiC) multilayered structures, as a function of the a-Si well layer thickness. As the layer thickness is decreased, the diffusion coefficient gradually decreases, while the lifetime drastically increases by more than one order of magnitude than that in thick unlayered a-Si. These behaviors suggest that the carrier transport is determined both by carrier interaction with shallow traps at a-Si/a-SiC interfaces and by quantum-size effect through weakened carrier coupling with deep states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.98698
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  • 10
    Electronic Resource
    Electronic Resource
    Role of grain-boundary sliding in diffusional creep of polycrystals (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 7547-7552 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The kinetics of deformation caused by grain-boundary sliding and diffusion is discussed for a two-dimensional model polycrystal. It is shown that boundary sliding is a prerequisite to induce the bulk diffusion. The sliding must also occur concurrently with the diffusion for a polycrystal to continue diffusional creep. Rate equations for deformation of the polycrystal are also formulated when both of the bulk and boundary diffusions are operative in addition to the boundary sliding. It is shown that the two diffusional processes are exclusive in general. Only when boundaries slide extremely fast, the strain rate of the polycrystal in a steady state becomes the simple sum of the strain rate achieved by the bulk diffusion and that by the boundary diffusion. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367519
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