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  • 1
    Electronic Resource
    Electronic Resource
    A submillimeter polychromator for plasma spectroscopy (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 3108-3116 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A 12-channel grating polychromator for the measurement of electron cyclotron emission on the Frascati tokamak upgrade (FTU) has been built. Three gratings can be exchanged remotely, to allow the instrument to cover three different spectral ranges (between 200 and 600 GHz) which correspond to the second harmonic of electron cyclotron emission for tokamak magnetic fields of 4, 6, and 8 T. Three sets of low-pass filters, whose cut-off frequencies are optimized for each grating, are used to cut the high diffraction orders. In order to exchange the filters together with the grating it was necessary to integrate the groups of filters with the polychromator itself. This has been done reducing the grating sizes and assembling them all closely on a moveable structure. The exchange of gratings and filters can be performed remotely via computer in few seconds without any lost of the alignment. InSb cryogenic hot-electron bolometers are used as detectors. The cryostat hold-time is more than 30 days. Spectral resolution λ/δλ is about 40 corresponding to a spatial resolution of δR≈2.3 cm. The minimum detectable temperature is about 10 eV at 20 kHz bandwidth. The spatial structure and temporal evolution of several kinds of fast temperature perturbations (as the ones due to magnetohydrodynamic activity, temperature fall during pellet injection and plasma disruption) have been measured on FTU by means of this diagnostic system. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147436
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  • 2
    Electronic Resource
    Electronic Resource
    Fourier transform spectroscopy applied to photoluminescence: Advantages and warnings (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 666-671 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A Fourier transform (FT) apparatus specially dedicated to photoluminescence measurements in the near infrared has been assembled. The details of the experimental setup and a comparison with a conventional dispersive apparatus are discussed. Advantages of the FT approach for photoluminescence measurements as well as warnings about limitations and artifacts are illustrated. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146839
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of different processes with hydrogen on the photoluminescence of GaAlAs:Si grown by molecular beam epitaxy (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 2797-2799 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a study on low-temperature photoluminescence (PL) of Si-doped Ga1−xAlxAs (n ∼ 1×1017 cm−3, 0.2≤x≤ 0.5) grown by molecular beam epitaxy (MBE) either in the presence and in the absence of a hydrogen backpressure and/or post-growth hydrogenated by exposure to a hydrogen plasma; we show that GaAlAs grown with hydrogen has a PL efficiency higher than that of material grown without hydrogen by a factor of up to 20; even more interestingly, the relative enhancement of transitions related to excitons and to shallow donors and acceptors is so large that the two kinds of PL spectra are qualitatively different. On the contrary, independently on whether material grown without hydrogen is post-growth hydrogenated, the spectral features of PL spectra are dominated by transitions involving relatively deep donors and/or acceptors. Our results suggest that the two treatments with hydrogen act on deep levels of different origin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103790
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  • 4
    Electronic Resource
    Electronic Resource
    Piezoelectric-induced quantum-confined Stark effect in self-assembled InAs quantum dots grown on (N11) GaAs substrates (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 1982-1984 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigate the optical properties of InAs self-assembled quantum dots grown on (N11)A/B GaAs substrates, by means of cw photoluminescence under different excitation power densities. We observe a sizeable blue-shift of photoluminescence band induced by increasing the photogenerated carrier density. The shift depends on the substrate orientation and exhibits a strong asymmetric dependence on the substrate termination. We attribute the photoluminescence blue-shift to a reverse quantum confined Stark shift of ground state transition energies in the quantum dots. This effect arises from the photogenerated charge screening of the built-in piezoelectric field present in such strained structures grown on high index planes. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1311814
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  • 5
    Electronic Resource
    Electronic Resource
    Thermally activated carrier transfer and luminescence line shape in self-organized InAs quantum dots (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 3354-3356 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigated the temperature dependence (10–180 K) of the photoluminescence (PL) emission spectrum of self-organized InAs/GaAs quantum dots grown under different conditions. The temperature dependence of the PL intensity is determined by two thermally activated processes: (i) quenching due to the escape of carriers from the quantum dots and (ii) carrier transfer between dots via wetting layer states. The existence of different dot families is confirmed by the deconvolution of the spectra in gaussian components with full width half maxima of 20–30 meV. The transfer of excitation is responsible for the sigmoidal temperature dependence of the peak energies of undeconvoluted PL bands. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117304
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  • 6
    Electronic Resource
    Electronic Resource
    Photoluminescence determination of the Be binding energy in direct-gap AlGaAs (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 3120-3122 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Be binding energy [EABe(x)] as a function of the Al content in AlxGa1−xAs has been determined by photoluminescence measurements of direct-gap Be-doped AlxGa1−xAs (0≤x≤0.315) samples grown by molecular beam epitaxy. It has been found EABe(x)=27.5+98x2 (meV) which is systematically lower than other literature values. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120265
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  • 7
    Electronic Resource
    Electronic Resource
    Be doping of (311)A and (100) Al0.24Ga0.76As grown by molecular beam epitaxy (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 4215-4217 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The use of Be as a p-type dopant in AlxGa1−xAs and in modulation doped heterostructures grown by molecular beam epitaxy on (311)A oriented substrates is investigated. Photoluminescence and electrical measurements reveal that Be is incorporated as an acceptor in (311)A oriented AlxGa1−xAs with a slightly greater efficiency than in (100) oriented AlxGa1−xAs. The optical properties of the (311)A samples are better than those of the (100) oriented samples. An estimate of the Be binding energy yields 32±4 meV at x=0.240±0.004. A two-dimensional hole gas with a very high mobility (250 000 cm2/Vs at 100 mK) and with clear fractional quantum hall effect is formed in the modulation of Be doped heterostructures grown on the (311)A orientation. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116990
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  • 8
    Electronic Resource
    Electronic Resource
    Carrier transfer and photoluminescence quenching in InAs/GaAs multilayer quantum dots (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 1307-1309 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A detailed study of the carrier transfer and photoluminescence (PL) quenching in stacked InAs/GaAs quantum dots (QDs) is presented. Vertically aligned QD structures, grown by atomic layer molecular beam epitaxy, with different numbers N of dot planes and different spacer thicknesses (d) were prepared and studied. The dependencies of carrier transfer from the GaAs barriers to the InAs QDs and of the PL quenching channels on the design parameters N and d have been identified by performing continuous wave and time-resolved PL measurements. We have found that both the radiative recombination and capture efficiency into the QDs are reduced by increasing N and by decreasing d, as a consequence of the deterioration of the interdot GaAs spacers induced by stacking. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1290385
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  • 9
    Electronic Resource
    Electronic Resource
    Room-temperature visible luminescence from silicon nanocrystals in silicon implanted SiO2 layers (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 851-853 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the observation of visible-light emission at room temperature from high fluence (0.3–3×1017 cm−2) Si+ implanted thermal SiO2 layers grown on silicon substrates. Significant blue-light emission and an intense broad luminescent band with a peak beyond 750 nm are observed after annealing at high temperature (T≥1000 °C). The red-light emission, present only in the highest fluence implant, is attributed to the luminescence emitted from silicon nanocrystals produced by silicon precipitation. The presence of silicon nanocrystals is confirmed by transmission electron microscopy. Significant blue-light emission is visible after thermal annealing in the 1×1017 cm−2 fluence implant. The peak position shifts from 490 to 540 nm by increasing the annealing cycles temperature. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113408
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  • 10
    Electronic Resource
    Electronic Resource
    A dynamic simulation model of the world jute economy
    Amsterdam : Elsevier
    European Economic Review 16 (1981), S. 303-331 
    Details
    ISSN: 0014-2921
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Economics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0014-2921(81)90006-4
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