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  • Articles: DFG German National Licenses  (28)
  • 1985-1989  (28)
  • 1
    Electronic Resource
    Electronic Resource
    The effect of heat treatment on redistribution of fast diffusing impurities in polycrystalline silicon (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 942-944 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of heat treatment on minority carrier surface recombination velocity in polycrystalline silicon samples has been examined in the temperature range (600–900 °C) using the electron-beam induced-current mode of a scanning electron microscope. Minority carrier trap center density, calculated from minority carrier surface recombination velocity data, varying from 8.9×1011 to 6.37×1013 cm−2 have been measured. A finite variation in the minority carrier trap center density indicates that metallic impurities diffuse to the surface from the bulk of the sample. The activation energy of impurity atom diffusion is found to be 1.1±0.1 eV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341900
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    High-field torque magnetometry measurements on Y1.8Er0.2Fe14B (abstract) (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3778-3778 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Y1.8Er0.2Fe14B is an interesting system in that the tendency of the Er ions to order in the basal plane is almost exactly canceled at low temperatures by the uniaxial anisotropy of the iron sublattice.1 We have performed torque magnetometry measurements in all three principal planes of a single crystal of this material at temperatures from 4 to 300 K in magnetic fields up to 60 kG, which is adequate to produce near saturation even in directions away from the principal axes, thus allowing us to determine the magnetocrystalline anisotropy free energy as a function of orientation and temperature. The free energy data were compared with calculations using the full set of crystal field parameters allowed by symmetry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338640
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Determination of minority-carrier diffusion length in a p-silicon wafer by photocurrent generation method (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 3550-3552 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A nondestructive method to determine the diffusion length of minority carriers in a p-silicon wafer is outlined. This novel method is based on creating an accumulation layer on one side and an inversion layer on the other side of the wafer by depositing thin semitransparent layers of high (e.g., palladium) and low (e.g., aluminum) workfunction metals, respectively. The wafer acquires a structure akin to p+-p-n+ and is capable of generating a photocurrent when illuminated. The photocurrent Isc (where sc represents short circuit) as a function of the intensity Pin of a monochromatic radiation incident on the accumulation layer (p+) side of the wafer is measured. The diffusion length L is determined from the slope of the Jsc vs Pin curve. The values of L so determined were compared with that determined from the measurement of spectral response by illuminating the wafer from the inversion layer (n+) side and were found to be in excellent agreement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337610
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Phase-separated Fe and Co particles in a BN matrix (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3320-3322 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using co-sputtering, 10–300 A(ring) particles of Fe and Co have been prepared in an insulating BN matrix. The Fe particles have the α-Fe structure. The saturation magnetic moment of the iron particles per at. % Fe was found to be approximately independent of the Fe concentration and equal to the value of α-Fe. The system undergoes a metal–nonmetal transition at approximately 40 vol % Fe. For concentrations of Fe particles above this threshold the temperature dependence of the resistivity is metallic and the room-temperature coercivity is large (50–100 Oe). For the Co particles, the room-temperature coercivity is about twice as large as Fe above the metal–nonmetal threshold. Below the metal–nonmetal threshold the particles behave as superparamagnets and the coercivity is approximately zero.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338977
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Mössbauer study of spin reorientation in Y1.8Er0.2Fe14B (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3568-3570 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fe57 Mössbauer spectra were taken from 300 K down to 4.2 K for two single-crystal samples of Y1.8Er0.2Fe14B, one cut with its [001] axis normal to the surface, the other with its diagonal of [100], [010], and [001] axes normal to the surface. The former sample has shown that the angle between the Fe spin and the [001] increases continuously below ∼90 K. This qualitatively agrees with the spin reorientation (i.e., the easy axis of magnetization rotates away from the [001] toward [100] on cooling below ∼90 K) which have already been observed by torque magnetometry. The latter sample has shown that the Fe spin actually rotates continuously; abrupt change of Fe spin direction, which have been already suggested to occur in Er2Fe14B, does not occur in Y1.8Er0.2Fe14B. The samples were so thick that the intensity of strong absorption lines were saturated. We have derived a formula with which the saturation effect can be corrected in order to determine the angle of the Fe spin direction correctly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338728
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    The ferro/ferricyanide couple in an aluminum chloride-1-methyl-3-ethylimidazolium chloride ambient-temperature molten salt (1989)
    s.l. : American Chemical Society
    Inorganic chemistry 28 (1989), S. 421-426 
    Details
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ic00302a011
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Magnetic properties of R2Fe14B single crystals (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 4091-4093 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A whole new class of high-performance permanent magnet materials is based on the ternary tetragonal structure R2Fe14B, where R is one of the rare-earth elements. We have successfully grown single crystals of this structure with R=Y, Nd, and Tb. Y is a nonmagnetic rare-earth substitute, while Nd and Tb couple ferro- and ferrimagnetically, respectively, relative to the iron moment. All three of the compounds have [001] easy axes at room temperature, although the Nd compound exhibits a spin reorientation away from the [001] below about 150 K. Nd2Fe14B has a saturation induction at room temperature of 16.2 kG, which places an upper limit of approximately 65.6 MGOe on the energy product obtainable by magnets based on that material. While Tb2Fe14B exhibits a smaller magnetization because of ferrimagnetic coupling of the rare earths and the iron, it also has an extremely large magnetic anisotropy which is nearly temperature independent between 4.2 and 300 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.334681
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Low- and high-field transport properties of pseudomorphic InxGa1−xAs/In0.52Al0.48As (0.53≤x≤0.65) modulation-doped heterostructures (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 1945-1949 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have grown pseudomorphic InxGa1−xAs/In0.52Al0.48As modulation-doped heterostructures by molecular-beam epitaxy under carefully controlled growth conditions. Mobilities as high as 13 900, 74 000, and 134 000 cm2/V s are measured at 300, 77, and 4.2 K in a heterostructure with x=0.65. Shubnikov–de Haas measurements indicate that the change in the effective mass with increasing In is not significant and is not responsible for the enhancement in mobilities. We believe that the improvement results from reduced alloy scattering, reduced intersubband scattering, and reduced impurity scattering, all of which result from a higher conduction-band offset and increased carrier confinement in the two-dimensional electron gas. The high-field electron velocities have been measured in these samples using pulsed current-voltage and pulsed Hall measurements. A monotonic increase in velocities is observed both at 300 and 77 K with an increase of In content in the channel. Velocities of 1.55×107 and 1.87×107 cm/s are measured at 300 and 77 K, respectively, in a In0.65Ga0.35As/In0.52Al0.48As modulation-doped heterostructure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341748
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Magnetic anisotropy energy in single crystal Y1.8Er0.2Fe14B (invited) (abstract) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3139-3139 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: There has been considerable interest in tetragonal R2Fe14B compounds as a basis for a new class of permanent magnet materials because of the unusually large energy products they exhibit at room temperature for certain rare-earth substitutions. The origin of the high-energy products is directly related to the large saturation magnetization and magnetic anisotropy energy. The magnetocrystalline anisotropy energy is believed to be directly related to an interaction between the 4f-electrons and the crystal field: however, to date few if any direct comparisons have been made between the experimental magnetic anisotropy and crystal field theory. The reason being that the large anisotropy energy makes it very difficult to use conventional torque magnetometry techniques to determine the angular dependence of the magnetic free energy, particularly at low temperatures where the higher-order terms become important. In this investigation we determine the angular dependence of the magnetic free energy as a function of temperature for Y1.8Er0.2Fe14B using high field (6 T) torque magnetometry techniques and make a direct comparison of the free energy with the energy calculated using a model based on crystal field theory. Y1.8Er0.2Fe14B was chosen because the Fe and Er sublattice anisotropy energies nearly cancel at low temperatures making it possible to measure anisotropy. Excellent agreement was obtained between the model and experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340867
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    Paper (German National Licenses)
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of a GaAs buffer layer grown at low substrate temperatures on a high-electron-mobility modulation-doped two-dimensional electron gas (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 943-945 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Sidegating in GaAs integrated circuits can be eliminated in molecular beam epitaxially grown structure with the incorporation of a GaAs buffer layer grown at low substrate temperatures (200–300 °C). We have grown two films which were identical except one had the low-temperature buffer layer included in the film structure. The films were modulation-doped heterojunctions designed to produce a high-mobility two-dimensional electron gas. The electrical characteristics of the two-dimensional electron gas were identical for the two samples. No deleterious effect on the mobility or carrier density was observed with the incorporation of the low-temperature buffer layer. At 4.2 K both films exhibited carrier densities of 4×1011 cm−2 and mobilities of (1.4–1.7)×106 cm2/V s in the dark. After a brief illumination at 4.2 K, the samples exhibited carrier densities of 5×1011 cm−2 and mobilities of (1.6–2.0)×106 cm2/V s. These electron mobilities are comparable to the highest electron mobilities ever obtained at these electron densities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101358
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    Paper (German National Licenses)
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