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  • 1
    Electronic Resource
    Electronic Resource
    Transfer-matrix analysis of waveguide phase modulator using the linear electro-optic effect of asymmetric quantum wells (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 4903-4905 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The phase modulation of asymmetric quantum-well embedded waveguides is studied. In order to accurately analyze the modulation from quantum wells and optimize the performance of waveguide modulators, a transfer-matrix method is developed to calculate the bias-controlled phase modulation of waveguides with an arbitrary refractive index distribution. The refractive index change may include those from free-carrier effects and the nonlinear effects of bulk material and quantum wells. The linear electro-optic effect introduced by asymmetric quantum wells can potentially be used to improve the frequency performance of semiconductor waveguide phase modulators.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357271
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  • 2
    Electronic Resource
    Electronic Resource
    Transverse diffusion measurements and comparisons with Monte Carlo simulation and Gram–Charlier calculations for Cs+ ions drifting in He gas (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 9547-9550 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The ratio of the transverse diffusion coefficient to the mobility, DT/K, has been experimentally determined for Cs+ ion drifting in He gas at E/N (electric field to neutral gas number density ratio) values ranging from 5 to 140 Td. Results at 303 K are reported with an overall accuracy of ±4%. The DT/K results were effectively corrected for longitudinal end effects existing in the drift tube. In addition, Monte Carlo simulation (MCS) calculations were made for the mobility and transport coefficients using the Koutselos, Mason, and Viehland (KMV) interaction potential as input. Comparisons of MCS results and available kinetic theory's Gram–Charlier results with the present and previous experimental data give an indication of the validity and accuracy of the present potential. The theoretical results did not reproduce the experimental curve very well, suggesting that the proposed potential for the Cs+–He pair should be modified. Further comparisons of the transverse and longitudinal diffusion coefficients indicate that the Gram–Charlier approach of kinetic theory is quite accurate even for the large ion-neutral mass ratio. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473855
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  • 3
    Electronic Resource
    Electronic Resource
    Electronic Structure and Symmetry in Nickel L Edge X-ray Absorption Spectroscopy: Application to a Nickel Protein (1994)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 116 (1994), S. 1918-1923 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00084a036
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  • 4
    Electronic Resource
    Electronic Resource
    NiFe2O4 nanoparticles formed in situ in silica matrix by mechanical activation (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 6015-6020 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nanocrystalline nickel ferrite (NiFe2O4) particles were successfully synthesized in situ in an amorphous silica matrix by mechanical activation at room temperature. Phase development in the amorphous precursors, derived via a modified sol–gel synthesis route, with increasing mechanical activation time was studied in detail by employing transmission electron microscopy, x-ray diffraction, and Raman spectroscopy. NiFe2O4 nanoparticles of 8.05 nm in mean particle size with a standard deviation of 1.24 nm, which were well dispersed in the silica matrix, were realized by 30 h of mechanical activation. The phase formation of nanocrystalline NiFe2O4 particles involves the nucleation of Fe3O4 in amorphous silica at the initial stage of mechanical activation, followed by the growth of nickel ferrite by incorporation of Ni2+ caions into Fe3O4. Their magnetic anisotropy, surface spin disorder, and cation distribution are investigated by considering both the strain imposed by silica matrix and the buffer effect during mechanical activation. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1462853
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  • 5
    Electronic Resource
    Electronic Resource
    Transparent magnetic composites of ZnFe2O4 nanoparticles in silica (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 4169-4174 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Uniformly dispersed zinc ferrite nanoparticles were successfully synthesized in a silica matrix with both the magnetic properties and optical transparency designed in the visible wavelength region. The phases and morphologies of these zinc ferrite particles were examined using x-ray diffraction, Raman spectroscopy and transmission electron microscopy. A much lower formation temperature of ZnFe2O4 in nanocomposites was observed in this study compared to in conventional ceramic processing. The particle size of zinc ferrite was found to vary with the initial drying temperature, suggesting that a well-established silica network provides more confinement to the growth of ZnFe2O4 particles. The magnetic properties, measured at both 78 K and room temperature, exhibit strong dependence on the particle size, and are related to the unusual cation distribution and the surface effect of nanoparticles. The optical properties of the nanocomposites can be adjusted by varying the concentration of the zinc ferrite nanoparticles. Their absorption coefficient remains below 400 cm−1 in the red visible light region. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1404423
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  • 6
    Electronic Resource
    Electronic Resource
    Oxides as thermionic sources of Mg+, Ca+, Sr+, and Ba+ ions (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 2879-2882 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Group II metal oxides (MgO, CaO, SrO, and BaO) were coated on tungsten or tantalum filaments to form thermionic emitters of positive metal ions. The choice between tungsten and tantalum for optimum performance was empirically found to depend on the oxide material. Total ion emission current and ion purity were generally found to increase with temperature. A stable source of high purity (up to 97%) Ba+ ions could be obtained from the BaO-coated filament at 1800 °C after 150 min of heating. At 1600 °C, the SrO-coated filament could produce a relatively stable ion current and purity of 97% of Sr+ ions. Very pure (99.8%) Ca+ ions were emitted at 1950 °C. However more stable ion current though less pure ions (87% of Ca+ at 1800 °C) were obtained at lower temperatures. MgO-coated filaments using tungsten or tantalum wires were found to be unsuitable as a source of Mg+ ions. All the filaments of MgO, CaO, SrO, and BaO were found to produce larger ion current and higher ion purity at higher temperatures. In general, the relative isotopic abundances of ions produced by a thermionic source are reproduced by the natural isotopic abundances of the corresponding metal. It implies that the slight differences in the nuclear masses of the isotopes do not introduce any significant effect on their ion production efficiency. Between tantalum and tungsten as a choice for the filament material, tantalum was found to be a better choice for Ba+ and Sr+ ions, while tungsten was better for Ca+. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145572
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  • 7
    Electronic Resource
    Electronic Resource
    Thermionic aluminosilicate sources of Tl+ ions (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 5249-5251 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Thermionic filament sources of Tl+ ions were made using tungsten wire coated with synthetic thallium aluminosilicates in the β-eucryptite (Tl2OAl2O32SiO2) and two other compositions (2Tl2OAl2O32SiO2 and 2Tl2OAl2O34SiO2). Three different methods for the production of aluminosilicate melts were used. The performance characteristics as thermionic emission sources of Tl+ ions based on total emission current and purity of ion emission as functions of time and filament surface temperature were studied and compared. Our results indicated that the sample of composition ratio of 2Tl2OAl2O32SiO2, which was produced by resistance heating under atmospheric pressure in air, is an optimum Tl+ ion source at temperatures between 1150 and 1350 °C after 150 h of continuous heating. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146093
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  • 8
    Electronic Resource
    Electronic Resource
    Design of solid/liquid–liquid/solid trilayer systems for the measurement of diffusion coefficients in liquid metals (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 3002-3005 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new method for investigation of diffusion processes in liquid metals with solid/liquid–liquid/solid trilayer systems is described. The design of this kind of trilayers enables diffusion processes with no effects from gravity-induced convection and Maragoni-convection conditions. The Ta/Zn–Sn/Si trilayers were prepared and the interdiffusion of liquid zinc and tin at 500 °C was investigated. The interdiffusion coefficients range from 1.0×10−4 to 2.8×10−4 mm2/s, which are less than previous values measured by capillary reservoir technique under 1 g environment where various kinds of convection exist. It is the removing of disturbances of these kinds of convection that brings about the precise interdiffusion coefficients in liquid metals. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149047
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  • 9
    Electronic Resource
    Electronic Resource
    Strain relaxation of GaNxAs1−x on GaAs (001) grown by molecular-beam epitaxy (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 5302-5304 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A series of samples consisting of a strained layer of GaNxAs1−x of different thickness, covered by a GaAs cap layer of 100 nm were grown by molecular-beam epitaxy. The samples have been characterized by high-resolution x-ray diffraction and simulations based on the dynamical theory in order to determine the strain relaxation in GaNxAs1−x layers. It is found that there is a huge difference between the critical thickness determined by x-ray diffraction and the theoretical calculations according to the Matthews and Blakeslee model. The critical thickness of GaNxAs1−x on GaAs is ten times smaller than the theoretical value. The strain relaxation is a crucial point that affects the quality of GaNAs. Photoluminescence measurements are in good agreement with the x-ray diffraction results. The optical properties degraded rapidly when the GaNxAs1−x thickness exceeded the critical thickness determined above. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371516
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  • 10
    Electronic Resource
    Electronic Resource
    Effects of rapid thermal annealing on the optical properties of GaNxAs1−x/GaAs single quantum well structure grown by molecular beam epitaxy (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 245-248 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of rapid thermal annealing (RTA) on the optical properties of GaNxAs1−x/GaAs strained single quantum well (SQW) was studied by low-temperature photoluminescence (PL). The GaNxAs1−x/GaAs SQW structures were prepared by dc active nitrogen plasma assisted molecular beam epitaxy. PL measurements on a series of samples with different well widths and nitrogen compositions were used to evaluate the effects of RTA. The annealing temperature and time were varied from 650 to 850 °C and 30 s to 15 min, respectively. Remarkable improvements of the optical properties of the samples were observed after RTA under optimum conditions. The interdiffusion constants have been calculated by taking into account error function diffusion and solving the Schrodinger equation. The estimated interdiffusion constants D are 10−17–10−16 cm2/s for the earlier annealing conditions. Activation energies of 6–7 eV are obtained by fitting the temperature dependence of the interdiffusion constants. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371852
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