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  • 1
    Electronic Resource
    Electronic Resource
    Observation of step configuration conversion on single-domain Si(001) 1×2 surface by scanning tunneling microscope (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 3336-3338 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have observed a conversion of step configuration of 3.5° miscut Si(001) surface after depositing several monolayers of Ge by using a scanning tunneling microscope. For a 3.5° miscut Si(001) surface, terraces are spaced by double-atom height steps and all dimer rows, either on the upper terrace or on the lower terrace of a step, are normal to the step edge, defined as single-domain (1×2) surface. After depositing 2 ML of Ge, the surface is still single domain, but dimer rows have changed their direction, running parallel to the step edge and single domain (2×1) appeared. The reason for such conversion is attributed to the strain that existed on the epilayer of Ge. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117298
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  • 2
    Electronic Resource
    Electronic Resource
    Ultrafast low-temperature grown AlGaAs/GaAs photorefractive quantum wells using point defects as capture centers (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 1366-1368 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: At a medium substrate temperature of 400 °C and a lower As flux, we have grown an ultrafast AlGaAs/GaAs photorefractive multiple quantum well (MQW) structure by molecular beam epitaxy. The as-grown sample exhibits strong photorefractive effect under the transverse Frantz–Keldysh geometry. A peak electroabsorption of 2100 cm−1 is measured in the as-grown sample in an 11 kV/cm dc electric field, and the peak photorefractive diffraction efficiency can be 1.2%. After postgrowth annealing, the photorefractive effect becomes weak and disappears in samples annealed above 700 °C. Using optical transient current spectroscopy, deep levels are measured in these samples. It is found that deep levels are stable against annealing until 700 °C. Using a pump-probe technique, carrier lifetimes are measured at room temperature. We find that the as-grown sample has a lifetime of 20 ps, while the 700 °C annealed sample has a lifetime of more than 200 ps. The ultrafast lifetime in the as-grown sample is caused by point defects, not by As clusters. Our result show that AlGaAs/GaAs MQW structure grown around 400 °C has better performance of the photorefractive effect. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124695
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of Si doping on optical characteristics of cubic GaN grown on (001) GaAs substrates (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 3765-3767 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The photoluminescence (PL) properties of Si-doped cubic GaN with different carrier concentrations were investigated at room temperature. The epilayers were grown on GaAs (001) by radio-frequency molecular-beam epitaxy. It was found that when the carrier concentration is increased from 5×1015 to 2×1018 cm−3, the PL peak shifted towards low energy, from 3.246 to 3.227 eV, and the PL linewidth increased from 77.1 to 121 meV. The PL peak shift is explained by the band gap narrowing effect due to the high doping concentration. The PL linewidth includes two parts: one is doping concentration independent, which is caused by the imperfection of samples and phonon scattering; the other is doping concentration dependent. We assign the second part to the broadening by the microscopic fluctuation of the doping concentration. The experimental measurements are in good agreement with the model. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126774
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  • 4
    Electronic Resource
    Electronic Resource
    Two-wave mixing in Stark geometry photorefractive quantum wells under a magnetic field (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 2185-2187 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using a modified method for measuring photorefractive two-wave mixing gain, we presented the experimental demonstration of nonreciprocal energy transfer during two-wave mixing under an external magnetic field. The nonreciprocal energy transfer is observed with mixing gain approaching 164 cm−1 and showed the characteristics of nonlinearity and saturation. A simple model of resonant tunneling and ultrafast carrier lifetime was proposed to explain these results. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126292
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  • 5
    Electronic Resource
    Electronic Resource
    Influence of (001) vicinal GaAs substrates on the optical properties of defects in low-temperature grown GaAs/AlGaAs multiple quantum wells (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 504-506 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoluminescence (PL) spectroscopy and carrier lifetime measurement has been used to characterize optical properties of defects in the low-temperature (LT) grown GaAs/AlGaAs multiple quantum well structures. Two sets of samples were grown at 400 °C by molecular beam epitaxy on nominal (001) and miscut [4° off (001) towards (111) A] GaAs substrates, respectively. After growth, samples were subjected to 30 s rapid thermal annealing at 600–800 °C. It is found that after annealing, two defect-related PL features appear in the samples grown on nominal (001) GaAs substrates, but not in those grown on miscut (001) GaAs substrates. The carrier lifetimes are about 31 and 5 ps in as-grown samples grown on nominal and miscut (001) GaAs substrates, respectively. The different PL spectra and carrier lifetimes in two sets of samples are attributed to different structures of the AsGa-like defects formed during LT growth. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124430
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  • 6
    Electronic Resource
    Electronic Resource
    Conformation of bilirubin amides from circular dichroism spectroscopy
    Amsterdam : Elsevier
    Tetrahedron 44 (1988), S. 4679-4688 
    Details
    ISSN: 0040-4020
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/S0040-4020(01)86170-6
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  • 7
    Electronic Resource
    Electronic Resource
    Novel synthesis of bilirubin mono-esters
    Amsterdam : Elsevier
    Tetrahedron Letters 28 (1987), S. 1047-1050 
    Details
    ISSN: 0040-4039
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/S0040-4039(00)95907-0
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  • 8
    Electronic Resource
    Electronic Resource
    Conformation of bilirubin esters from circular dichroism spectroscopy
    Amsterdam : Elsevier
    Tetrahedron Letters 28 (1987), S. 4033-4036 
    Details
    ISSN: 0040-4039
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/S0040-4039(01)83854-5
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  • 9
    Electronic Resource
    Electronic Resource
    Impact of the convection-wind-evaporation feedback on surface climate simulation in general circulation models (1996)
    Springer
    Climate dynamics 12 (1996), S. 299-312 
    Details
    ISSN: 1432-0894
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The wind-evaporation-convection feedback in the tropics is demonstrated to strongly affect the mean state of surface climate in atmospheric general circulation models. The feedback is shown to be very effective in channeling perturbations from one component of the climate system to other components, e.g., from evaporation to surface wind and from atmospheric convective activity to evaporation. It also provides an effective channel to pass on atmospheric perturbations in the middle and upper troposphere to the surface. As an illustration, it is shown that surface evaporation over tropical oceans is connected with cloud absorption of shortwave radiation through this feedback. Insufficient shortwave cloud absorption, causing excessive shortwave radiation at the surface as is common in most of the climate models, leads to excessive evaporation. Quantitatively, sensitivity of evaporation to short-wave cloud absorption, when averaged over the whole tropics, can be described by an approximate balance of variations in atmospheric radiative cooling and latent heating. This balance is achieved by the impact of radiation on convection, and then on the surface wind and evaporation. This mechanism calls for the need to include atmospheric processes far beyond the surface for improvements of the quality of surface climate simulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231104
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  • 10
    Electronic Resource
    Electronic Resource
    Impact of the convection-wind-evaporation feedback on surface climate simulation in general circulation models (1996)
    Springer
    Climate dynamics 12 (1996), S. 299-312 
    Details
    ISSN: 1432-0894
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract. The wind-evaporation-convection feedback in the tropics is demonstrated to strongly affect the mean state of surface climate in atmospheric general circulation models. The feedback is shown to be very effective in channeling perturbations from one component of the climate system to other components, e.g., from evaporation to surface wind and from atmospheric convective activity to evaporation. It also provides an effective channel to pass on atmospheric perturbations in the middle and upper troposphere to the surface. As an illustration, it is shown that surface evaporation over tropical oceans is connected with cloud absorption of shortwave radiation through this feedback. Insufficient shortwave cloud absorption, causing excessive shortwave radiation at the surface as is common in most of the climate models, leads to excessive evaporation. Quantitatively, sensitivity of evaporation to shortwave cloud absorption, when averaged over the whole tropics, can be described by an approximate balance of variations in atmospheric radiative cooling and latent heating. This balance is achieved by the impact of radiation on convection, and then on the surface wind and evaporation. This mechanism calls for the need to include atmospheric processes far beyond the surface for improvements of the quality of surface climate simulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003820050110
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