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  • 1
    Electronic Resource
    Electronic Resource
    Interfacial reactions and thermal stability of ultrahigh vacuum deposited multilayered Mo/Si structures (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4072-4077 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Interfacial reactions and thermal stability of ultrahigh vacuum deposited multilayered Mo/Si structures have been investigated by high resolution transmission electron microscopy in conjunction with fast Fourier transform and autocorrelation function analysis. For samples with nominal atomic ratios Mo:Si=1:2 and 3:1, well defined multilayered Mo/Si structures were obtained after annealing at 250 °C for 30 min. On the other hand, distinct multilayered MoSi2/Si structure was formed only for Mo:Si=1:2 samples after annealing at 650 °C for 1 h. Multiphases were observed to simultaneously form in samples annealed at 400–500 °C. After 600 °C annealing for 1 h, tetragonal MoSi2 was the only silicide phase observed for the Mo:Si=1:2 samples, whereas both tetragonal and hexagonal MoSi2 were present in Mo:Si-3:1 samples. The stability of the multilayered Mo/Si structures was found to depend critically on the atomic ratios of constituent elements, bilayer period, and annealing conditions. The results are interpreted in terms of the delicate balance among intermixing of constituent atoms, silicide formation, and crystallization of silicon. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361835
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  • 2
    Electronic Resource
    Electronic Resource
    Study of the orientational relaxation dynamics in a nonlinear optical copolymer by means of a pole and probe technique (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 1773-1778 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report measurements on the isothermal relaxation dynamics of the electro-optic coefficient of electric field poled polymeric films. The studied copolymer is a side-chain Disperse Red 1/poly–methyl–metacrylate combination. The isothermal relaxation is shown to follow a Kohlrausch–Williams–Watts stretched exponential dependence, whose parameters are strongly dependent on temperature. The average decay constant is shown to follow an Arrhenius temperature dependence below the glass transition Tg, while it is described by a Vogel–Fulcher–Tamann–Hesse above Tg. The values of the decay constant confirm a much better stability of the polymer orientation with respect to guest-host systems. The relaxation is shown to be due to a broad distribution of relaxation rates, the width of which can be qualitatively described by an empirical relation, which has already been used for guest-host systems. The measurement technique permits monitoring relaxation in a standard dielectric relaxation configuration and performing unconventional poling of the samples. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362987
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  • 3
    Electronic Resource
    Electronic Resource
    Crystal structure and magnetism of LaCo13−x−yFexSiy compounds (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 336-341 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The crystal structure and magnetic properties of LaCo13−x−yFexSiy compounds were investigated by means of x-ray powder diffraction and magnetization measurements. The substitution of Si for Co induces an order–disorder transition from the cubic NaZn13-type to its tetragonal derivative structure, while the substitution of Fe for Co does not induce such a phase transition. After annealing treatment, the homogeneous range of the cubic phase is narrowed and that of the tetragonal phase is extended. From crystallographic and thermodynamic points of view, the sta- bility of the cubic and the tetragonal phases is discussed. The measured magnetic moment of LaCo13−x−yFexSiy coincides well with the theoretical prediction based on the magnetic valence model. Within the framework of this model, LaCo13−x−yFexSiy compounds can be considered as strong ferromagnets and their magnetic moment can be theoretically predicted. The composition dependence of Curie temperature is discussed within the mean field approximation. At higher iron concentration the decrease of Curie temperature with Fe concentration might be attributed to the increase of the number of antiferromagnetically coupled Fe–Fe pairs and the decrease of the ferromagnetic coupling between transition metal atoms. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362786
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  • 4
    Electronic Resource
    Electronic Resource
    Magnetic structure and site occupancies in YFe11−xCoxTi (x=1,3,7,9) (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 2155-2160 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The crystal and magnetic structures of the system YFe11−xCoxTi have been investigated by high-resolution neutron powder diffraction for the compositions x=1, 3, 7, and 9. All compounds have the ThMn12 type structure, with space group symmetry I4/mmm. The distribution of the atoms over the independent crystallographic sites was found to be significantly different from random, with a strong preference for Ti to be in the 8i site and Co in the 8j and 8f sites. This behavior can be explained in terms of the enthalpy of formation of binary alloys. The magnetic moments are parallel to the c axis for the compositions x=1, 3, 9, and lie in the a-b plane for x=7. No evidence of additional nuclear or magnetic phase transitions was observed for sample YFe4Co7Ti down to 20 K. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371023
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  • 5
    Electronic Resource
    Electronic Resource
    A neutron powder diffraction study of the system La2(Co1−xFex)16Ti for x=0.0, 0.2, and 0.4 (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 1226-1229 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nuclear and magnetic structures of La2(Co1−xFex)16Ti have been studied by neutron powder diffraction for the compositions x=0.0,0.2,0.4. The compound crystallizes with the symmetry of space group R3¯m. Site occupancy results show significant departures from a purely statistical distribution, with the Ti atoms located in sites which interact weakly with La, and with the Co atoms occupying preferentially the sites with strong La interaction. These results are consistent with the enthalpies of formation of equiatomic alloys of rare earth and 3d elements. The spin ordering at all compositions and temperatures is ferromagnetic. At room temperature the moments are aligned along the c axis for the compositions x=0.0 and x=0.2, and form an angle of about 57° with c for x=0.4. This tilt angle is a function of temperature and the moment is aligned along c at 11 K, moving gradually towards the a,b plane as the temperature increases. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370875
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  • 6
    Electronic Resource
    Electronic Resource
    Structural and microstructural characterization of a high-Tc superconducting YBaSrCu3O7−δ compound (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 3593-3597 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transmission electron microscopy (TEM), energy dispersive analysis of x ray (EDS), x-ray diffraction, electrical resistance, and magnetic susceptibility measurements were applied to characterize the structure and microstructures of a high-Tc superconducting YBaSrCu3O7−δ compound. The sintered samples were found to be predominantly of a single phase with a modified perovskite structure. Combined EDS/TEM and high-resolution lattice imaging with computed image simulation data showed that the atomic ratio of Sr and Ba atoms is about unity and Ba sites in YBa2Cu3O7−δ compound were partially substituted by Sr atoms in the three-layer perovskite structure, in agreement with the results of a previous neutron diffraction study. It was also found that the marked contrast difference in high-resolution images along [100] and [010] directions of the high-Tc oxygen-deficient superconducting crystals can be used to advantage to distinguish [100] and [010] directions of the modified perovskite structure in TEM. Lattice defects such as twins and dislocations were observed and analyzed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341394
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of growth temperature on luminescence and structure of self-assembled InAlAs/AlGaAs quantum dots (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 2048-2050 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of growth temperature on the optical properties of self-assembled In0.65Al0.35As/Al0.35Ga0.65As quantum dots is studied using photoluminescence and electroluminescence spectra. With the growth temperature increasing from 530 to 560 °C, the improvement of optical and structural quality has been observed. Furthermore, edge-emitting laser diodes with three stacked InAlAs quantum dot layers grown at different temperature are processed, respectively. For samples with quantum dots grown at 560 °C, the continuous wave operation is obtained up to 220 K, which is much higher than that of ones with InAlAs islands grown at 530 °C and that of the short-wavelength quantum-dot laser previously reported. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1388021
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  • 8
    Electronic Resource
    Electronic Resource
    Anomalous temperature dependence of photoluminescence from InAs quantum dots (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 2529-2532 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Self-assembled InAs quantum dots are fabricated on a GaAs substrate by molecular beam epitaxy. The dots are covered by several monolayers of In0.2Ga0.8As before a GaAs cap layer and an in situ postgrowth annealing is performed to tune the emission to higher energy. The temperature dependence of photoluminescence from this structure demonstrates a slower redshift rate of the peak position, a gradual broadening of the linewidth and an abnormal enhancement of integrated intensity as the temperature is increased from 15 to 300 K. These phenomena are closely related to the introduction of an InGaAs layer and to the intermixing of In and Ga atoms during annealing. We propose a model to explain the unusual increase in PL intensity, which fits the experimental data well. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1288231
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  • 9
    Electronic Resource
    Electronic Resource
    Structural transformations of Bi2CuO4 induced by mechanical deformation (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 3155-3158 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Structural transformation of α-Bi2CuO4 (a=8.4996 Å, c=5.8172 Å, space group P4/ncc) during ball milling was investigated by powder x-ray diffraction and thermal analysis. It is shown that α-Bi2CuO4 first transforms into an amorphous phase; and then transforms into a new phase (designated by β-Bi2CuO4) with milling time. The new phase appears to be isostructural to (La,Sr)2CuO4 and has a tetragonal cell with cell parameters a=3.869 and c=13.83 Å. It is a metastable phase which can transform back into α-Bi2CuO4 at 650 °C. No superconductivity was observed above 5 K for both as-milled samples and oxygen-annealed β-Bi2CuO4. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369692
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  • 10
    Electronic Resource
    Electronic Resource
    Real-time pole and probe assessment of orientational processes in electro-optic polymers (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2765-2767 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electro-optic properties of polymer films are measured by an original technique whereby a periodic sequence of poling and probing steps permits alternation of the application of orientation and dephasing potentials. Relaxation dynamics of the electro-optic coefficient of Red–Acid–Magly crosslinkable polymer films is studied as a function of the temperature of the samples. The time constant of the decay τ as measured at several temperatures is found to follow a Vogel–Fulcher–Tamann—Hesse dependence, for temperatures above glass transition. Poling the samples in the presence of a pulsed electric field leads to a r33 electro-optic coefficient as high as 6 pm/V. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114586
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