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  • Articles  (67)
  • Wiley-Blackwell  (29)
  • American Institute of Physics (AIP)  (24)
  • Cambridge University Press
  • International Union of Crystallography
  • 2005-2009
  • 1990-1994  (67)
  • 1960-1964
  • 1991  (33)
  • 1990  (34)
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  • 2005-2009
  • 1990-1994  (67)
  • 1960-1964
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  • 1
    Electronic Resource
    Electronic Resource
    Magnetic measurements with a SQUID magnetometer: Possible artifacts induced by sample-holder off-centering : 35th annual conference on magnetism and magnetic materials San Diego, California (USA) 29 Oct − 1 Nov 1990 (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5088-5090 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Asymmetries in sample holders used for magnetic measurements on magnetometers based on induction methods, such as those equipped with SQUID sensors, can lead to substantial errors and/or important artifacts which resemble phase transitions. They occur under the conditions for which sample and/holder have signals of opposite sign, but are nearly equal in magnitude. The most serious errors can occur often, but not exclusively, for compounds having intermediate magnetic dilution. We present here a general discussion of the problem illustrated by measurements of a polyoxometallate with the known Keggin structure K6[Fe(III)W12O40]⋅nH2O, done on a SHE VTS model 905. While one of the obvious solutions to this problem is the use of holders with a signal much smaller than that of the sample, it would be preferable if, in addition, the holder had a response of the same sign as that of the sample, for all temperatures and fields measured.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348132
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  • 2
    Electronic Resource
    Electronic Resource
    Si impurity-induced layer disordering of Alx Ga1−x -GaAs quantum-well heterostructures by As-free open-tube rapid thermal annealing (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 6199-6206 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Data are presented describing Si impurity-induced layer disordering (IILD) and Al-Ga interdiffusion in AlxGa1−x As-GaAs quantum-well heterostructures (QWHs) using open-tube rapid thermal annealing (900–1000 °C) in a flowing N2/H2 ambient. The data show that Al-Ga interdiffusion is enhanced by n-type crystal doping and suppressed by p-type doping. By surrounding the active layers of the heterostructure with layers of opposite doping, we show that the surrounding layers modify the interdiffusion by controlling the diffusion of point defects to the active layers of the heterostructure. Data are presented showing the effects of dielectric encapsulation (SiO2, Si3N4 ) on Al-Ga interdiffusion. The data show that regardless of doping SiO2 enhances interdiffusion as compared to Si3N4. To achieve more thorough layer intermixing of AlxGa1−x As-GaAs QWHs, Si IILD is also investigated in the high-temperature As-poor regime. The experimental data show that in a high-temperature As-poor annealing ambient, little or no Si diffusion occurs from an elemental Si source in contact with a p-type GaAs QWH cap layer. To achieve Si diffusion under these conditions requires removal of the GaAs cap and the use of Al-reduced SiO2 or Si3N4 as a Si diffusion source. Based on secondary-ion mass spectroscopic measurements, direct comparison of Si diffusion from closed-tube (825 °C, 48 h) and open tube (1000 °C, 10 min) anneals shows increased Si incorporation and layer disordering at higher temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346911
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  • 3
    Electronic Resource
    Electronic Resource
    Generation of high-energy x-radiation using a plasma flow switch (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 1999-2007 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experiments with coaxial plasma guns at currents in excess of ten megamperes have resulted in the production of high-voltage pulses (0.5 MV) and hard x radiation (10–200 keV). The x-radiation pulse occurs substantially after the high-voltage pulse suggesting that high-energy electrons are generated by dynamic processes in a very high speed ((approximately-greater-than)106 m/s), magnetized plasma flow. Such flows, which result from acceleration of relatively low-density plasma (10−4 vs 1.0 kg/m3) by magnetic fields of 20–30 T, support high voltages by the back electromotive force-u×B during the opening switch phase of the plasma flow switch. A simple model of classical ion slowing down and subsequent heating of background electrons can explain spectral evidence of 30-keV electron temperatures in fully stripped aluminum plasma formed from plasma flows of 1–2 × 106 m/s. Similar modeling and spectral evidence indicates tungsten ion kinetic energies of 4.5 MeV and 46 keV electron temperatures of a highly stripped tungsten plasma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348773
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  • 4
    Electronic Resource
    Electronic Resource
    Si incorporation in laser-melted AlxGa1−xAs-GaAs quantum well heterostructures from a dielectric source (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 6174-6178 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Data are presented describing the incorporation of Si in locally laser-melted AlxGa1−xAs-GaAs quantum well heterostructures from a thin-film dielectric source. The composition of the melted material, the effects of the Si source (SiO2 or Si3N4) on impurity incorporation, and the doping behavior are examined via secondary-ion mass spectroscopy, electron dispersion x-ray spectroscopy, transmission electron microscopy, and scanning electron microscopy. The data indicate that upon melting, a (Si)y(AlxGa1−xAs)1−y alloy is formed from which impurity-induced layer disordering may be effected. After annealing the melt region is found to contain crystalline segregates, which are attributed to rapid thermal quenching of the melt. Applications of these results to the fabrication of buried-heterostructure lasers by laser-assisted disordering are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346907
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  • 5
    Electronic Resource
    Electronic Resource
    Two-point quasifractional approximant in physics. Truncation error (1991)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 32 (1991), S. 1470-1477 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The quasifractional approximation method is developed in a systematic manner. This method uses simultaneously the power series, and at a second point, the asymptotic expansion. The usual form of the approximants is two or more rational fractions, in terms of a suitable variable, combined with auxiliary nonfractional functions. Coincidence in the singularities in the region of interest is pursued. Equal denominators in the rational fractions is required so that the solution of only linear algebraic equations is needed to determine the parameters of the approximant. An upper bound is obtained for the truncation error for a certain class of functions, which contains most of the functions for which this method has been applied so far. It is shown that quasifractional approximants can be derived as a mixed German and Latin polynomial problem in the context of Hermite–Padé approximation theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.529304
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  • 6
    Electronic Resource
    Electronic Resource
    Native oxide stabilization of AlAs-GaAs heterostructures (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1199-1201 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Data are presented on the stabilization of AlAs-GaAs heterostructures against atmospheric (destructive) hydrolysis using the native oxide that can be formed (N2+H2O, 400 °C, 3 h) on the AlAs layer. The ∼0.1-μm-thick native oxide formed from the AlAs layer is shown to be stable with aging (∼100 days), while unoxidized samples degrade through the AlAs (0.1 μm) down into the GaAs as deep as ∼1 μm. Relative to oxides formed (∼25 °C) on AlAs (or AlxGa1−xAs, x (approximately-greater-than) 0.7) under atmospheric conditions (hydrolysis), oxides formed (via N2 +H2O) at higher temperatures ((approximately-greater-than)400 °C) are much more stable and seal the underlying crystal (e.g., GaAs).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105213
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  • 7
    Electronic Resource
    Electronic Resource
    Absence of 13C incorporation in 13CCl4-doped InP grown by metalorganic chemical vapor deposition (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 1760-1762 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Intentional carbon doping of low-pressure metalorganic chemical vapor deposition (MOCVD) grown InP has been attempted with a 500 ppm mixture of 13CCl4 in high-purity H2, which has been used to obtain carbon-acceptor concentrations as high as 1×1019 cm−3 in GaAs. Under growth conditions similar to those used for heavy carbon incorporation in GaAs, injection of 13CCl4 into the growth reactor during growth of InP did not produce any measurable change in the carrier concentration of the InP epitaxial layers or any change in the 13C concentration above the 13C background in secondary-ion mass spectroscopy analysis. These results support previous low-temperature photoluminescence measurements of high-purity InP in which no residual carbon acceptor is observed under many growth techniques and growth conditions, and hence support the hypothesis that carbon is not incorporated in InP grown by MOCVD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103092
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  • 8
    Electronic Resource
    Electronic Resource
    Carbon tetrachloride doped AlxGa1−xAs grown by metalorganic chemical vapor deposition (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 836-838 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A dilute mixture of CCl4 in H2 has recently been shown to be a suitable carbon doping source for obtaining p-type GaAs grown by metalorganic chemical vapor deposition (MOCVD) with carbon acceptor concentrations in excess of 1×1019 cm−3. To understand the effect of growth parameters on carbon incorporation in CCl4-doped AlxGa1−xAs, carbon acceptor concentration was studied as a function of Al composition, growth temperature, growth rate, and CCl4 flow rate using electrochemical capacitance-voltage profiling. The carbon incorporation as a function of Al composition, growth temperature, and CCl4 flow rate was also measured by secondary-ion mass spectroscopy. All layers were grown by low-pressure MOCVD using TMGa and TMAl as column III precursors, and 100% AsH3 as the column V source. Increased Al composition reduced the dependence of carbon concentration on the growth temperature. Reduced growth rate, which resulted in substantially decreased carbon acceptor concentrations in GaAs, had an insignificant effect on the carrier concentration of Al0.4Ga0.6As. A linear relationship between hole concentration and CCl4 flow rate in AlxGa1−xAs for 0.0≤x≤0.8 was observed. These results are interpreted to indicate that adsorption and desorption of CCly (y≤3) on the AlxGa1−xAs surface during crystal growth plays an important role in the carbon incorporation mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103321
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  • 9
    Electronic Resource
    Electronic Resource
    Epitaxial growth of aligned polydiacetylene films on anisotropic orienting polymers (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 131-133 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report an epitaxial method for orienting thin films of polydiacetylenes on ordinary alignment polymers that have been stretched by rubbing. By selectively removing the alignment polymer using standard photolithographic techniques, we show that it is possible to obtain well-oriented polydiacetylene films in desired regions. Typical values for the birefringence are 0.14±0.01 for epitaxially grown films, enough to allow the formation of gratings and channel waveguides on patterned surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103051
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  • 10
    Electronic Resource
    Electronic Resource
    Layer disordering of n-type (Se) and p-type (C) AlxGa1−xAs-GaAs superlattices by S diffusion (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 1720-1722 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Data are presented showing limited layer disordering (or intermixing) of S-diffused Se-doped or C-doped AlxGa1−xAs-GaAs superlattices. The S diffusion is characterized via secondary-ion mass spectroscopy, shallow angle beveled cross sections, and absorption measurements. Limited intermixing of column-III-site atoms (Al(arrow-right-and-left)Ga) as well as minimal displacement of the column-V-site acceptor C is observed. The S diffusion depth is much greater than that of the layer disordering, the magnitude of which is similar to that of native-defect vacancy-assisted disordering (vacancy VIII).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103126
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