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  • 1
    Electronic Resource
    Electronic Resource
    Effects of quantum mechanical coupling on the optical properties of vertically stacked V-groove quantum wires (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 772-776 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of the quantum mechanical coupling on the optical properties of vertically stacked InGaAs/GaAs V-shaped quantum wires have been studied by means of photoluminescence and photoluminescence-excitation spectroscopy. The experimental results have been analyzed by a simple theoretical model based on an analytical procedure. We found that by decreasing the barrier thickness (Lb) between the wires, the vertical coupling induces a splitting of the single wire levels into symmetric and antisymmetric states characterized by a polarization anisotropy. Furthermore, a clear shift of the coupled levels and a narrowing of the spectral linewidth are observed with a decrease in Lb. These findings are consistent with the theoretical predictions. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373736
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  • 2
    Electronic Resource
    Electronic Resource
    Structural study of InGaAs/GaAs quantum dots grown by metalorganic chemical vapor deposition for optoelectronic applications at 1.3 μm (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 4341-4348 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the influence of difference growth conditions on the two-dimensional to three-dimensional growth mode transition for a specific class of InGaAs/GaAs quantum dots (QDs) optimized for applications to optical devices operating around 1.3 μm (In content x(approximate)0.5). The dots are grown by low-pressure metalorganic chemical vapor deposition on GaAs substrates. We demonstrate that the critical layer thickness corresponding to optimized single-QD layer structures (i.e., with reduced wetting layer thickness and high uniformity) can be controlled by kinetic effects. The optimized growth conditions allow us to grow six-layers stacked QD structures as active material for the fabrication of a light emitting devices operating around 1.3 μm at room temperature. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1351861
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  • 3
    Electronic Resource
    Electronic Resource
    Dependence of the emission wavelength on the internal electric field in quantum-dot laser structures grown by metal–organic chemical-vapor deposition (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 1435-1437 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We show that the combination of different electric fields in In0.5Ga0.5As/GaAs quantum-dot electroluminescent devices dramatically blueshifts the emission wavelength even though the photoluminescence occurs at the expected value of 1.3 μm at room temperature. Systematic photoluminescence (PL), electroluminescence (EL), and photocurrent measurements demonstrate that the electric field associated with the built-in dipole in the dots, directed from the base of the dots to their apex, and the device junction field lead to the depletion of the ground state. As a consequence, structures grown on n-type GaAs substrates exhibit electroluminescence only from the excited states (whereas the photoluminescence comes from the ground level). Instead, by growing the same device structure on p-type GaAs substrates, i.e., by reversing the direction of the built-in electric field of the device, the effect of the permanent dipole is strongly reduced, thus allowing us to obtain EL emission at the designed wavelength of 1.3 μm at 300 K, coincident to the PL. This effect expands the possibilities for the achievement of efficient lasing in the spectral region of interest for optical transmission. The electric field associated to the dipole moment is estimated to be around 150 kV/cm. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1400088
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  • 4
    Electronic Resource
    Electronic Resource
    Photodetectors fabricated from a self-assembly of a deoxyguanosine derivative (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 3541-3543 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A metal–semiconductor–metal (MSM) photodetector has been fabricated using as the semiconductor, a self-assembled layer of a DNA basis, namely a deoxyguanosine derivative, deposited between two gold electrodes. These were defined lithographically on a SiO2 substrate, separated by a distance of about 120 nm. The resulting self-assembled guanosine crystal has been deposited in such a way to achieve striking semiconducting properties. We show that with these conditions, the I–V characteristics are independent of the crystal orientation. The device shows a high current response (differential resistance at room temperature ranges in MΩ) which is symmetric with respect to bias sign and dependent on the illumination conditions. This behavior can be explained by taking into account the standard MSM theory and its applications as a photodetector. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1374232
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  • 5
    Electronic Resource
    Electronic Resource
    Wavelength control from 1.25 to 1.4 μm in InxGa1−xAs quantum dot structures grown by metal organic chemical vapor deposition (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 1382-1384 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This letter reports on the realization of long-wavelength InGaAs quantum dots (QDs) fabricated by metal organic chemical vapor deposition. By controlling the In incorporation in the QD layers and/or in the barrier embedding the QDs, we are able to tune the wavelength emission continuously from 1.25 to 1.4 μm at room temperature. Efficient stacking of dots emitting at 1.3 μm is also demonstrated. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1352698
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  • 6
    Electronic Resource
    Electronic Resource
    Low temperature tool for photoluminescence mapping with submicron resolution (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 2610-2612 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have developed a local probe technique in order to realize photoluminescence maps with submicron resolution at temperatures as low as 25 K. To this end a closed cycle He cryostat has been modified in order to damp mechanical vibrations to avoid spatial resolution losses. Both the optical laser pump and the collected signal are fiber-optic coupled. Photoluminescence maps are provided by a motorized X-Y translation stage that scans the microscope objective over the sample surface. The overall resolution of the microphotoluminescence (μ-PL) system is ∼500 nm, by considering the contributions of the laser focused spot size (λ=325 nm), the cryostat vibrations, and the motorized stage resolution. The system is described and two low temperature μ-PL experiments on quantum wires and quantum dot nanostructures are presented and discussed. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1369631
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  • 7
    Electronic Resource
    Electronic Resource
    Crystal structure of cavansite dehydrated at 220°C (1975)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 31 (1975), S. 1598-1602 
    Details
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567740875005766
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  • 8
    Electronic Resource
    Electronic Resource
    Crystal structure of mazzite dehydrated at 600°C (1975)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 31 (1975), S. 1603-1608 
    Details
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567740875005778
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  • 9
    Electronic Resource
    Electronic Resource
    Stacking variations in cancrinite minerals (1979)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 35 (1979), S. 825-828 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: TEM reveals (0001) stacking faults and periodic superstructures in cancrinite-related minerals, afghanite and franzinite, which are interpreted as aperiodic or periodic displacements of the hexagonal [(Si,Al)6O12] ring units. Franzinite also shows a superstructure when the structure is projected onto the xy plane; satellites occur in the hk0 diffraction patterns.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739479001868
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  • 10
    Electronic Resource
    Electronic Resource
    Octahedral cation ordering in olivine at high temperature. I: in situ neutron single-crystal diffraction studies on natural mantle olivines (Fa12 and Fa10) (2000)
    Springer
    Physics and chemistry of minerals 27 (2000), S. 623-629 
    Details
    ISSN: 1432-2021
    Keywords: Key words Olivine ; Order/disorder ; High-temperature cation partitioning ; Neutron diffraction (single crystal)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract  Crystallographic determinations on natural olivine single crystals of mantle composition and origin, carried out by in situ neutron diffraction at high temperature, show that the octahedrally co-ordinated Fe2+ and Mg cations undergo two successive trends of cation ordering with increasing temperature. An initial slight preference of Fe2+ for site M1, up to a temperature of about 850 °C, is followed by a reverse-ordering reaction with a site preference exchange between the two cations. The cross-over between the two regimes of ordering, corresponding to a situation of complete disorder, occurs at about 900 °C. Above this temperature Fe2+ progressively and strongly segregates into site M2 up to 1300 °C, the practical limit of the experimental setup utilized in the experiments. Care was taken to ensure that no chemical changes occurred in the crystals (i.e. oxidation), as testified by Mössbauer spectroscopy determinations carried out before and after the heat treatment. The cation-ordering behaviour is reflected in temperature-dependent changes of geometrical and atomic displacement parameters occurring in the octahedral sites M1 and M2. A thermodynamical explanation of this behaviour is proposed in terms of a prevailing vibrational contribution to entropy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690000110
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