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  • 1
    Electronic Resource
    Electronic Resource
    Growth of high-Tc YBa2Cu3Oy films with an off-axis sputtering configuration (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 8419-8422 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using an off-axis rf sputtering configuration, we have prepared in situ high-Tc YBa2Cu3O7−y (YBCO) films with a relatively large deposition rate. The sputtering gas was a mixture of Ar and O2 (7:3) and the substrates were MgO(100) and SrTiO3(100). We found that the distance from the target to the substrate, d, is a key factor in the deposition rate. By decreasing d to a value of about 1.5–2.5 cm, we obtained a deposition rate as great as 2000–2500 A(ring) per hour with an rf power of 120 W and at a total pressure 100–200 mTorr. The transport behaviors of the as-grown YBCO films under magnetic fields are reported. The activation energy derived from the resistive transition in magnetic fields is thickness dependent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353411
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  • 2
    Electronic Resource
    Electronic Resource
    Optoelectronic properties of ZnSe/ZnMgSSe multiple quantum wells (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 3725-3729 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optoelectronic properties of undoped ZnSe/ZnMgSSe multiple quantum wells (MQWs) grown by molecular beam epitaxy on (001) GaAs substrates have been investigated by photoluminescence, photoconductivity, and persistent photoconductivity (PPC) measurements. The features related to the band-to-band excitonic and impurity-related transitions of ZnSe/ZnMgSSe MQWs are observed and discussed. In addition, the parameters that describe the temperature dependence of the interband transition energy and broadening function of the excitonic feature are evaluated. PPC has been observed in undoped ZnSe/ZnMgSSe MQWs. The decay kinetics of the PPC effect can be described by a stretched-exponential function, Ippc(t)=Ippc(0)exp[−(t/τ)β], (0〈β〈1). Through the study of the PPC effect under various conditions, such as different temperature, different photon energy of photoexcitation, and different ZnSe well width, we identify that the carrier excitation from the defect level in ZnMgSSe barrier layer into the ZnSe well layer is the origin of the PPC effect in ZnSe/ZnMgSSe MQWs. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1350416
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  • 3
    Electronic Resource
    Electronic Resource
    Optical quenching of the photoconductivity in n-type GaN (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 3404-3408 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Results of optical quenching of photoconductivity measurements in undoped n-type and Se-doped GaN epitaxial thin films are presented. The spectral distribution of quenching phenomena shows a broadband centered around 1.26 eV. Transient changes in photoconductivity on application or removal of the quenching radiation are shown to exhibit a metastable behavior. The results reveal that the origin of the optical quenching phenomena is closely related to the defects corresponding to the persistent photoconductivity effects and the yellow luminescence band observed in most n-type GaN. In addition, this result indicates that these defects can have multiple charge states. It is found that the quenching ratio increases with increasing Se-doping concentration. We point out that the origin of the defects responsible for the optical quenching can be attributed to nitrogen antisite and/or Ga vacancy. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372358
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  • 4
    Electronic Resource
    Electronic Resource
    Optical properties of Si-doped GaN films (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 6124-6127 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Results of the front-side and back-side photoluminescence (PL) measurements in a set of Si-doped GaN epifilms are presented. From the back-side PL spectrum, the enhancement of the yellow emission implies that most of the intrinsic defects responsible for the yellow band exist mainly near the interface between the buffer layer and the epilayer. We also found that the intensity of the yellow luminescence decreases with increasing Si dopants, which is consistent with the fact that the microscopic origin of the yellow emission can be attributed to gallium vacancies VGa. In additions, our investigations reveal that the potential fluctuations, that give rise to the effect of band-gap narrowing and linewidth broadening, are mainly caused by randomly distributed doping impurities instead of other defects. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371662
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  • 5
    Electronic Resource
    Electronic Resource
    Longitudinal and transverse Hall resistivity of epitaxial SrRuO3 films (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5792-5794 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the longitudinal ρxx and transverse Hall ρxy resistivities of epitaxial SrRuO3 (SRO) under varied applied fields. The Hall resistivity, ρxy, is proportional to 1/(T−Tc) in the paramagnetic state of SRO films, where Tc is the asymptotic Curie temperature. The Lorentz resistivity Δρ(H)Lorentz in a fixed magnetic field in the ferromagnetic regime of SRO films is proportional to A(1−T/Tc)p with p∼0.5. RH is positive for T〉125 K and changes sign at T∼125 K for SRO films. The RH remains negative down to low temperatures. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369921
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  • 6
    Electronic Resource
    Electronic Resource
    Surface modification of YBa2Cu3Oy thin films with a scanning tunneling microscope (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 2535-2537 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a systematic modification of thin YBa2Cu3Oy films with a scanning tunneling microscope. The samples include YBa2Cu3Oy films on MgO(001) and YBa2Cu3Oy/PrBa2Cu3Oy bilayer films on SrTiO3 (001). The bias voltage of the tip was kept negative and varied from −600 to −1200 mV. The tip was operated in a constant tunneling current mode with tunneling current 0.3–0.7 nA and scanning rate 1 Hz. Modification of the surface begins with nucleation of holes, or at the edge of a dislocation or protrusion on the surface, and is achieved by successively scanning a fixed area. We show the image obtained from an atomic force microscope which can help us look into the mechanism of the modification.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357566
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  • 7
    Electronic Resource
    Electronic Resource
    Microwave effects on YBa2Cu3Oy Josephson junctions with step-edge, bi-epitaxial, and sandwich geometries (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 1871-1877 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fabrication and characterization of YBa2Cu3Oy Josephson junctions with step-edge, bi-epitaxial, and sandwich geometries are performed in this study to investigate the effects of microwave irradiation on the I–V characteristics. I–V curves under microwave irradiation reveal Shapiro steps. The width of the constant voltage steps were modulated by the microwave power. The period of the magnetic induction ΔB detected from the V–Φ curves for superconducting quantum interference devices is temperature dependent. Additionally, Tc and Ic of the proximity sandwich junctions are enhanced by the microwave irradiation. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360222
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  • 8
    Electronic Resource
    Electronic Resource
    Persistent photoconductivity in InGaN/GaN multiquantum wells (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 338-340 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optical properties of undoped InGaN/GaN multiquantum wells (MQWs) have been investigated by photoconductivity, photoluminescence, and photoluminescence excitation measurements. We report the observation of persistent photoconductivity (PPC) in InGaN/GaN MQWs and show that the PPC effect arises from In composition fluctuations in the InGaN well layer. From the analysis of the decay kinetics, the localization depth caused by composition fluctuations has been determined. Compared with the results of complementary absorption and photoluminescence measurements, it is found that the quantum-confined Stark effect due to piezoelectric field and composition fluctuations both exist in the InGaN/GaN MQWs. These two effects are responsible for the photoluminescence Stokes' shift in the InGaN well layers. Here, we provide a unique way to distinguish the individual contribution to the Stokes' shift for the piezoelectric field and composition fluctuations. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1340000
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  • 9
    Electronic Resource
    Electronic Resource
    Mechanism of luminescence in InGaN/GaN multiple quantum wells (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 3712-3714 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a firm evidence of luminescence from InN clusters in InGaN/GaN multiple quantum wells. Photoluminescence, photoluminescence excitation, and Raman scattering measurements have been employed to study the optical properties of InGaN/GaN multiple quantum wells. A careful examination of the low energy shoulders of the main peak luminescence reveals the fact that their separation is in good agreement with the longitudinal optical phonon energy of pure InN film measured by Raman scattering. A large Stokes-like shift between the emission peak energy and the absorption edge is found; it increases with increasing indium content. All these observations can be explained in a consistent way by the effect of localization due to self-organized InN clusters within InGaN layers. Our results thus strongly suggest that the emission mechanism of InGaN/GaN quantum wells originates from radiation recombination within the localized states of self-organized InN clusters. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126758
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  • 10
    Electronic Resource
    Electronic Resource
    Determination of nitrogen atom concentration in flowing gases (1986)
    s.l. : American Chemical Society
    Analytical chemistry 58 (1986), S. 2492-2495 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac00125a030
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