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  • 1
    Electronic Resource
    Electronic Resource
    Magneto-optical transitions in GaAs-AlGaAs coupled double quantum wells (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4920-4922 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetophotoluminescence excitation spectroscopy has been employed to study GaAs-AlGaAs coupled double quantum wells. The investigations were undertaken at liquid helium temperatures and in magnetic fields up to 15 T applied parallel to the growth direction. In zero magnetic field, under flat-band conditions, the spectrum is dominated by ground-state excitonic transitions between electron and hole states with envelope functions of the same symmetry. In a magnetic field, the oscillator strengths of excited excitonic states are enhanced and four series of transitions are observed. The spectral features corresponding to the ground state and the excited states have been analyzed and these results were utilized to determine the exciton binding energies for several excitonic transitions of different subbands in this coupled double quantum-well structure. A number of additional features are visible at higher magnetic fields; some of these peaks are believed to be associated with 2p exciton transitions between hole and electron states with envelope functions of opposite parity due to exciton mixing. A comparison is made between the experimental results and theoretical calculations which include these effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344733
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  • 2
    Electronic Resource
    Electronic Resource
    Photoluminescence from Si1−xGex strained layers grown by atmospheric pressure chemical vapor deposition (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 6201-6203 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low temperature photoluminescence due to the self-annihilation of bound excitons has been observed in Si1−xGex strained layers grown using atmospheric pressure chemical vapor deposition. Samples were grown at temperatures near 1000 °C with growth rates up to 1000 nm per minute allowing short growth times, thus preventing extensive interdiffusion at layer interfaces. Well-resolved, bulk-like photoluminescence spectra with narrow no phonon linewidths were observed from strained SiGe material indicating it to be of suitable electronic quality. For a sample consisting of 120 nm of Si0.92Ge0.08 capped with 90 nm of Si on a Si(100) substrate, the photoluminescence spectrum exhibited Si1−xGex bound exciton lines with resolved no phonon and transverse optic phonon components.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350433
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  • 3
    Electronic Resource
    Electronic Resource
    Calculation of the ferromagnetic resonance linewidth of barium ferrite : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6183-6185 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two microscopic models have been proposed to explain the large intrinsic linewidth of barium ferrite. The first is a two-magnon scattering process due to an intrinsic disorder associated with the unique trigonal bipyramidal site in the crystal. [E. Tsantes and L. M. Silber, J. Appl. Phys. 63, 3350 (1988)]. The second is the Kasuya–LeCraw relaxation process [S. P. Marshall, J. B. Sokoloff, and C. Vittoria, IEEE Trans. Magn. MAG-25, 3491 (1989)]. Both of these processes involve modulation of the single-ion anisotropy. Analytical calculations using simplified models for the acoustic magnon and phonon spectra fail to account for the linewidths characteristic of barium ferrite. In order to understand both of these relaxation processes as they relate to barium ferrite, we have calculated the full phonon spectrum for this crystal based on the rigid-ion model. The calculated reflectivity compares well with the infrared reflectivity data that we have taken. Using phonon modes that we have calculated and the magnon modes calculated previously [S. P. Marshall and J. B. Sokoloff, J. Appl. Phys. 67, 2017 (1990)], we have calculated the ferromagnetic resonance linewidth on the basis of the Kasuya–LeCraw mechanism and two-magnon scattering by fluctuating 2b-site ions. We find that the trigonal-site disorder scattering mechanism is able to account for the observed magnitude of the linewidth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348800
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  • 4
    Electronic Resource
    Electronic Resource
    Optical properties of buried cobalt disilicide layers in silicon (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7465-7469 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The optical reflectivity from highly conducting buried and exposed CoSi2 layers produced by Co ion implantation of Si substrates has been measured over the energy range 0.012–6.2 eV (0.2–100 μm). Both as-implanted and high temperature annealed heteroepitaxial layers were investigated. The frequency dependant optical constants associated with the CoSi2 films were derived from the multicomponent reflectivity spectra; the analysis accounted for the contributions from the Si-CoSi2 interfaces. A Drude term was used to describe the free carriers, and a classical oscillator model was included to simulate interband electronic transitions for the CoSi2. The plasma frequency and relaxation time of the free carriers were measured as a function of anneal conditions. A direct correlation between the effective carrier concentration and the measured channeling data from Rutherford backscattering was observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356616
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  • 5
    Electronic Resource
    Electronic Resource
    Infrared spectra in nonstoichiometric yttria-stabilized zirconia mixed crystals at elevated temperatures (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 1413-1417 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Infrared (IR) reflectivity measurements were undertaken on pure ZrO2 and stabilized ZrO2⋅Y2O3 solid solutions containing 3-, 4-, 7-, 12-, and 20-wt.% Y2O3 over 10–900 cm−1 region as a function of temperature up to 1400 °C. The observed IR active phonons are related to the phase transitions that depend on composition and temperature. Good agreement was achieved among IR, Raman scattering, and neutron scattering investigations. An IR reflectivity enhancement from 42% to 60% in the low-frequency region (10–110 cm−1) was found as the monoclinic(M)-tetragonal(T) martensitic transition was completed in pure ZrO2 and ZrO2⋅3-wt.% Y2O3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341839
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  • 6
    Electronic Resource
    Electronic Resource
    Low-frequency Raman spectra in disordered cubic zirconia at elevated temperatures (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 250-253 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Rayleigh wing broadening (quasielastic scattering) was found at high temperatures (650–1500 K) in cubic zirconia single-crystal ZrO2 fully stabilized with Y2O3; however, broadening was not observed in the two-phased cubic plus tetragonal zirconia crystals. We believe this can be interpreted as a disorder-order transition as the configuration goes from single-phase cubic-to-cubic plus tetragonal structure with less addition of Y2O3. Theoretical agreements were achieved by utilizing "rigid ion model'' and "decay model'' calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339190
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  • 7
    Electronic Resource
    Electronic Resource
    Neutron studies of "forbidden'' magnons in Pt3Mn, a three-dimensional metallic ferromagnet (abstract) (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3429-3429 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polarized neutron measurements are presented which show clearly that "forbidden'' and allowed magnons exist as underdamped excitations both below and above Tc in the three-dimensional metallic ferromagnet, Pt3Mn. ("Forbidden'' magnons are magnons created by neutrons polarized along the sample magnetization, which are forbidden at low temperature.) A model of magnons propagating through a crystal containing a 360° magnetization twist is studied, which indicates that "forbidden'' magnons can exist if the range of the short-range order is at least four lattice constants long, which is consistent with our experimental results and Edward's estimates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338742
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  • 8
    Electronic Resource
    Electronic Resource
    Strain studies of silicon-germanium epilayers on silicon substrates using Raman spectroscopy (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 1243-1245 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Atmospheric pressure chemical vapor deposition techniques have been used to grow electronic quality Si-Ge epilayers on Si substrates. The degree of tetragonal strain in the layers has been determined using Raman spectroscopy. The relative energy shift of the Si-Si phonon line associated with the Si1−xGex epilayers from a pseudoalloy of the same composition was used as a quantitative measure of the strain. Layer growth was found to be almost commensurate with the Si substrates for thicknesses in the region of ∼100 nm. For x(approximately-equal-to)0.1 the resulting films were highly strained and homogeneous. The strain diminished with increasing thickness and it was estimated that a layer would be fully relaxed when the thickness exceeded 3000 nm. The phonon linewidths provided information on the epilayer and interface quality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109784
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  • 9
    Electronic Resource
    Electronic Resource
    High pressure optical investigation of porous silicon (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 1435-1437 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have performed the first photoluminescence (PL) measurements under hydrostatic pressure up to 37 kbar at room temperature on several porous silicon (Si) samples fabricated under different etching conditions. A blue shift of the PL peak energy was observed in all samples from 0 to ∼20 kbar. Above ∼20 kbar, the PL peak energy appears to be constant or even to exhibit a small red shift with pressure in some samples. This pressure dependence of the PL peak energy of porous Si is different from the pressure induced red shift in the PL from the indirect band gap of the bulk Si crystal, or the red shift in the PL from amorphous Si. The intensity of the PL peaks showed a decrease with increasing pressure. We have also observed a red shift with time when a blue laser continuously illuminated the sample. These results on the pressure dependence of porous Si provide critical information for modeling and determining the electronic structure of porous silicon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108466
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  • 10
    Electronic Resource
    Electronic Resource
    Polarized neutron measurement of "forbidden'' magnon scattering in Pt3Mn (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3751-3752 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have employed inelastic scattering of polarized neutrons to study the nature of the magnetic response in the vicinity of the Curie temperature (TC=493 K) for the intermetallic ferromagnet Pt3Mn. The measurements were taken on the HB-1 triple-axis spectrometer at ORNL, with a field of 10 kOe applied along the scattering vector Q. For 0.9TC 〈T〈1.2TC we observed underdamped magnons not only with the conventional (+) spin-wave polarization but also with the "forbidden" (−) polarization, with an intensity difference I(+)−I(−) which is approximately proportional to the magnetization. Both these observations are in agreement with the slowly fluctuating spin-density theory of itinerant ferromagnetism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.334960
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