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  • 1
    Electronic Resource
    Electronic Resource
    Doping effect of viologen on photoconductive device made of poly (p-phenylenevinylene) (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 2871-2873 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the photovoltaic properties of the donor–acceptor composite system of poly (p-phenylenevinylene) (PPV) and viologen. We observed the significant enhancement of photocurrent with increasing the doping ratio of viologen. The maximum photocurrent of viologen-doped PPV was nine times as high as that of the pristine PPV. The maximum quantum yield and photosensitivity are 13% (electron/photon) and 0.05 A/W, respectively, at low bias voltage (−2 V). The increase of photocurrent is explained with the efficient charge separation that resulted from the transfer of photoexcited electrons from PPV to viologen. The mixture of PPV and viologen can be used as a sensitive photodiode material. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121486
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  • 2
    Electronic Resource
    Electronic Resource
    Nonswitching van der Pauw technique using two different modulating frequencies (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 2177-2178 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We present a nonswitching van der Pauw technique using two independent ac current sources and two lock-in amplifiers. This technique may be useful to measure the resistance of delicate samples that might be easily damaged by electric shocks induced from switching, and can be extended to measure the anisotropy of resistance. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149738
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  • 3
    Electronic Resource
    Electronic Resource
    Galvanomagnetic properties and magnetic domain structure of epitaxial MnAs films on GaAs(001) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4967-4969 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial MnAs films on GaAs(001) in the thickness range 20–200 nm were studied. Using ordinary and extraordinary Hall effect data to determine the field required for perpendicular saturation and saturation magnetizations reported elsewhere, we determined the shape anisotropy constant in the basal plane of the hexagonal structure to be 3.7(0.6)×105 erg/cm3 and the surface anisotropy constant to be −1.3(0.4) erg/cm2. The negative sign indicates thin enough films will be perpendicularly magnetized. By magnetic force microscopy of a 100 nm film we found stripe domains with 180° Bloch walls, thereby avoiding the hard c axis. The widths of the domains and the walls are 4.0(0.3) μm and 95(6) nm, respectively. In magnetoresistance, we observed behavior similar to other ferromagnets, namely peaks centered around the positive and negative coercive fields, and at fields beyond the coercive field a linear dependence on magnetic field. The electrical resistance showed rapid increase with temperature beginning about 5° below the Curie temperature (40 °C) caused by the change in crystal structure from hexagonal to orthorhombic. The resistivities are, respectively, 300(24) and 375(30) μΩ cm. Comparison with bulk values indicates the large lower temperature value is partly due to the presence of some orthorhombic phase observed in x-ray studies. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361605
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of coupling structure of Eu on the photoluminescent characteristics for ZnO:EuCl3 phosphors (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 668-670 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this study we have synthesized ZnO:EuCl3 phosphors under various sintering atmospheres and temperatures, and investigated the effect of coupling structure of Eu in ZnO upon the photoluminescent characteristics for the purpose of searching for optimum conditions towards pure red emission. The analysis of x-ray diffraction and photoluminescence spectra measurements indicate that, for ZnO:EuCl3 phosphors sintered in vacuum, Eu exists in the host lattice as EuOCl and effectively quenches the broad-band emission of the ZnO host, consequently isolating the red emission due to Eu3+ ion. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120833
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of oxidation process on interface roughness of gate oxides on silicon: X-ray reflectivity study (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 433-435 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the effects of the wet and dry oxidation processes on the interfacial roughness and time dependent dielectric breakdown (TDDB) characteristics of the poly-Si/SiO2/Si(100) trilayer. The interface roughness of the oxide layers buried under a thick poly-Si electrode has been investigated using an x-ray reflectivity technique. Analysis of x-ray reflectivity data for the trilayer samples and for a bare oxide film shows that interface roughness of poly-Si electrode/SiO2 interfaces depends on oxidation process while oxide layers have smooth SiO2/Si-subtstrate interfaces. TDDB of the SiO2 layer has also been observed to depend on the oxidation process, indicating that the interface roughness is a crucial factor affecting the TDDB characteristics. The wet oxidized SiO2 film is more stable to dielectric breakdown and has smoother interfaces than the dry oxidized sample. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120780
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  • 6
    Electronic Resource
    Electronic Resource
    Steady-state Nyquist theorem for multi-terminal nondegenerate semiconductor devices (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 8182-8194 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Formulas for the spectral intensities of the short-circuit thermal noise currents in arbitrarily shaped multi-terminal semiconductor devices under dc bias are derived by solving the Langevin-type Boltzmann transport equations. The derived formulas are valid when the carrier distributions are not far from the local equilibrium distributions. Measurement data on short-circuit thermal noise currents are obtained for a three-terminal silicon bulk device. A comparison between the calculated and experimental results is made and thereby the validity of our theory is confirmed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356518
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  • 7
    Electronic Resource
    Electronic Resource
    Compensation of shallow donors in dimethylaluminum methoxide-doped GaAs (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 5813-5819 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hall-effect and deep-level transient spectroscopy measurements have been performed on GaAs epilayers grown by organometallic vapor-phase epitaxy and intentionally doped with diethyltellurium and dimethylaluminum methoxide (DMAlMO). The DMAlMO doping was observed to compensate shallow tellurium donors for concentrations as high as 1019 cm−3, producing fully compensated high-resistivity epilayers. Seven DMAlMO-induced deep levels have been observed in the GaAs band gap with activation energies of 0.25, 0.30, 0.37, 0.40, 0.58, 0.74, and 0.93 eV. Less than 5% of all oxygen atoms were present in the layer in the form of isolated off-center substitutional oxygen corresponding to the 0.58 eV level. The major traps located at 0.74 and 0.93 eV below the conduction band have been attributed to complexes of aluminum and oxygen involving two and one aluminum atoms, respectively. Both of these levels are deep acceptors responsible for the compensation of shallow donors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358394
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  • 8
    Electronic Resource
    Electronic Resource
    Deposition of high-quality NiMnSb magnetic thin films at moderate temperatures (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 2740-2744 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin films of the ferromagnetic Heusler alloy NiMnSb, of interest for magnetic multilayer devices because of their predicted half-metallic (i.e., 100% spin-polarized) transport properties, have been successfully deposited by rf magnetron sputtering from a single composite target. A novel combination of low argon gas pressure, low deposition rates, and moderate substrate temperatures (250–350 °C) are shown to result in high-quality, low-roughness polycrystalline films of the C1b-type crystal structure, with thicknesses as low as 100 Å, without the need for any post-deposition annealing. The structural properties of these films, determined by x-ray diffraction and atomic force microscopy are presented as a function of deposition conditions. The magnetic properties and resistivity are consistent with bulk MiMnSb, which suggests that they will be effective as spin-polarized conducting layers in multilayer thin-film structures. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363977
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  • 9
    Electronic Resource
    Electronic Resource
    Reinvestigation and extension of the steady-state Nyquist theorem for multi-terminal semiconductor devices and its application to minimum noise figure in microwave field effect transistors (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 228-241 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The steady-state Nyquist theorem for multi-terminal semiconductor devices, which describes the short-circuit thermal noise currents in arbitrarily shaped multi-terminal semiconductor devices, is reinvestigated. The concept of the equipotential surfaces for small ac signals is found to be wrong, which forces us to introduce a new approach to find the equipotential surfaces for noise voltages. Using this new approach, we rederive the steady-state Nyquist theorem with the same results as in the previous derivation, and extend it to the hot carrier regime. Using the extended theorem, we express the minimum noise figure for microwave field effect transistors as a function of the measurable device parameters with no fitting constant. The derived minimum noise figure is shown to reduce to a simple form, which can also be used as an empirical relation with one fitting constant. This simple form can explain the experimental results very well in wide frequency ranges, and gives through a clear mathematical relation the empirically known requirements for the low noise design of microwave field effect transistors. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360936
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  • 10
    Electronic Resource
    Electronic Resource
    Deep-center oxygen-related photoluminescence in GaAs doped with dimethylaluminum methoxide during organometallic vapor phase epitaxy (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 2015-2021 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Infrared oxygen-related photoluminescence measurements of GaAs epilayers grown by organometallic vapor phase epitaxy (OMVPE) and intentionally doped with dimethylaluminum methoxide (DMALMO) are reported. The photoluminescence emissions at 1.08, 0.95, 0.81, and 0.62 eV are detected. The centers responsible for the emissions at 0.81 and 0.62 eV are tentatively attributed to Al–O–Ga and Al–O–Al, respectively, based on correlation with layer growth conditions. The growth parameters lead to information on the number of nearest-neighbor aluminum associated with oxygen. The Al–O–Ga center responsible for the 0.81 emission is also studied for AlxGa1−xAs(x=0.05–0.9) layers grown by OMVPE without DMALMO. The 0.81 eV emission is attributed to the transition from the conduction band to the Al–O–Ga center. The center shows the lattice relaxation exemplified by the Franck–Condon shift of 0.15 eV. The thermal ionization energy of this acceptor is determined to be 0.56 eV above the valence band. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360177
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