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  • Nature Publishing Group  (33)
  • American Institute of Physics (AIP)  (16)
  • ZBW – Leibniz Information Centre for Economics Kiel, Hamburg
  • 1990-1994  (31)
  • 1975-1979  (18)
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  • 1
    Digitale Medien
    Digitale Medien
    Low temperature magnetic force microscopy (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 2920-2925 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: We have built a low temperature scanning force microscope which is able to measure contact and noncontact forces using the dc modes of force microscopy. We demonstrate the capabilities of our instrument on a magneto-optical disk at room temperature and at 77 K. Using a ferromagnetic thin film tip, the topography and the micromagnetic stray field of the sample is measured using the dc modes of force microscopy. The topographic and magnetic data are precisely correlated. The circular bit structure and the natural domain structure between the homogeneously magnetized bits is clearly visible. A lateral resolution below 100 nm and a force resolution of 10−12 N is reproducibly achieved.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1144383
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  • 2
    Digitale Medien
    Digitale Medien
    Shock compression of tungsten and molybdenum (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 1721-1728 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: New high-pressure shock-wave data have been obtained for W and Mo. These data have been combined with previous data sets for these materials to extend the range of linear us–up fits for the Hugoniot to 480 GPa for Mo and 680 GPa for W. The shock-wave data, supplemented by the necessary thermodynamic information, have been used to generate several isotherms (100, 200,...1000 K). Tables of pressure versus relative volume up to 380 GPa suitable for comparison with statically obtained data are given.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.351203
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  • 3
    Digitale Medien
    Digitale Medien
    As-cast magnets based on Fe-Nd-C : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6447-6449 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Fe14Nd2C (Φ) shows structural and intrinsic magnetic properties comparable to Fe14Nd2B. The phase Fe14Nd2C is found in long-time-annealed samples only ((approximately-greater-than)20 d at 850 °C) because of nucleation difficulties and slow growth kinetics. Compared to the Fe-Nd-B system the phase relations in the Fe-Nd-C system are unfavorable to produce sintered or even as-cast magnet materials, as manifested in the phase diagram presented. Fe14Nd2C is in equilibrium with either ferromagnetic and/or very corrosive phases, therefore the pure Fe-Nd-C material is useless. This situation can be changed by the addition of several elements to the Fe-Nd-C material: boron (even in small amounts of ≈0.05 mass %) accelerates the formation of Φ and reduces annealing times from weeks to hours; Cu added in the correct amount leads to new phase relations between Φ and NdxCuy intermetallic compounds. These intermetallics are nonmagnetic and low melting. Starting from as-cast material using the knowledge about the influences of substituants on phase relations and kinetics, a heat treatment can be chosen that leads directly to an isotropic, magnetically hard material with a rather small grain size ((approximately-less-than)20 μm) and coercivities up to 1 T. The magnetization is comparable to isotropic Fe-Nd-B materials.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.349926
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  • 4
    Digitale Medien
    Digitale Medien
    Novel reflectance modulator employing an InGaAs/AlGaAs strained-layer superlattice Fabry–Perot cavity with unstrained InGaAs/InAlAs mirrors (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1608-1610 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We present a novel approach to optoelectronic devices by combining mechanically stable strained and unstrained epitaxial multilayers. We illustrate our approach with an optical reflectance modulator based on an asymmetric Fabry–Perot resonator designed to operate near 1.06 μm. The resonator is grown on a mechanically relaxed buffer of In0.11Ga0.89As deposited on a GaAs substrate. For mirrors, quarter-wave stacks of In0.11Ga0.89As and In0.1Al0.9As, lattice matched to the buffer, are used. The Fabry–Perot cavity consists of an In0.23Ga0.77As/Al0.35Ga0.65As strained-layer superlattice whose planar lattice constant also matches the buffer. Our first device operates at 1.04–1.05 μm depending on lateral position across the wafer. The insertion loss at resonance is less than 2 db and a fractional modulation of over 60% has been achieved with a 4 V bias swing.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.105140
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  • 5
    Digitale Medien
    Digitale Medien
    Energy transfer in highly vibrationally excited acetylene: Relaxation for vibrational energies from 6500 to 13 000 cm−1 (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 389-396 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Vibrational overtone excitation of acetylene molecules to energies between 6500 and 13 000 cm−1 followed by interrogation of the excited states during collisional relaxation determines both the mechanism and rates of energy transfer. A pulsed visible or near-infrared laser excites a single rotational state of C2H2 in the region of the first (2νCH), second (3νCH), or third (4νCH) overtone of the C–H stretching vibration, and an ultraviolet laser probes the excited molecules by laser-induced fluorescence after a variable delay. The self-relaxation rate constant of about 9×10−10 cm3 molecules−1 s−1 is almost twice the Lennard-Jones collision rate constant and is nearly invariant with vibrational level. The energy-transfer rate constants from these population transfer measurements agree with those extracted from pressure-broadening data in both their size and insensitivity to vibrational state. Relaxation by the rare-gas atoms He, Ar, and Xe is nearly half as efficient as self-relaxation, suggesting that the internal structure of the collision partner is not particularly important in determining the relaxation rate. The invariance with vibrational level and the efficiency of rare-gas quenching indicate that rotational energy transfer is the most important relaxation pathway.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.463583
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  • 6
    Digitale Medien
    Digitale Medien
    ECR ion and free radical sources for MBE applications : International conference on ion sources (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 282-284 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A small 2.45 GHz ion/free radical source that has been specifically designed for MBE applications is described. The overall outside diameter of this cylindrical source is 5.8 cm (includes magnets and applicator) and the length is less than 15 cm. Thus, it fits through vacuum ports on existing MBE machines and can be placed near the substrate. The microwave discharge, which is created within a cylindrical quartz tube, is surrounded by rare-earth magnets and a tunable coaxial cavity applicator. Single or double accelerating grids can be placed on the 3.75-cm-diam discharge output producing an ion beam, or the discharge can be freely exhausted into the vacuum allowing the charged and excited species to diffuse onto the substrate for plasma and/or free radical processing. This device can operate at pressures as low as 10−5 Torr with A, O2, and N2 gases using only 50–150 W of incident power. The detailed description and the preliminary experimental test of this source is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1141322
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  • 7
    Digitale Medien
    Digitale Medien
    Automatic current control unit for electrodeposition (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3863-3865 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: In the course of research on the electrodeposition of ternary compound semiconductors the problem of electrolysis with up to four anodic partial current circuits arose, having different and differently changing resistances. The potential at the cathode as well as the ratio of the anodic partial currents had to be regulated. In order to handle this problem we developed an automatic electronic regulating unit, the circuit diagram of which is presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1141513
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  • 8
    Digitale Medien
    Digitale Medien
    Electric field dependent photocurrent and electroreflectance spectra of InGaAs/AlGaAs multiple strained quantum well structures (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 1245-1247 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We present results on excitonic transitions and confinement at high electric fields from photocurrent and electroreflectance spectra of an In0.17Ga0.83As/Al0.3Ga0.7As strained quantum well structure fabricated into a Schottky barrier diode. Up to the highest field attained, 1.7×105 V/cm, we observe a well-defined exciton line at the band edge (in contrast to data on similar GaAs/Al0.3Ga0.7As structures), a feature important for potential optoelectronic applications. At low fields, "allowed'' (Δn=0) transitions dominate the photocurrent spectra, but with increasing field "forbidden'' transitions (allowed because of reduced symmetry and valence-band mixing) grow in intensity and eventually dominate the above-gap response. In the electroreflectance spectra, the forbidden transitions are relatively strong, even at low field. The allowed above-gap transitions nearly vanish at low temperature because of the small field dependence of the higher lying quantum well energy levels.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.103498
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  • 9
    Digitale Medien
    Digitale Medien
    Electric-field-dependent electroreflectance spectra of visible-band-gap (InAlGa)P quantum-well structures (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 1824-1826 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We present results from the first studies of electric-field effects on optical transitions in visible-band-gap InGaP/InAlGaP multiple-quantum-well (MQW) structures. These structures, grown at 775 °C by metalorganic vapor phase epitaxy on (100) GaAs substrates misoriented 6° towards P(111〉〈111〉A, consist of nominally undoped MQWs surrounded by doped In0.49Al0.51P cladding layers to form p-i-n diodes. The Stark shifts of various allowed and forbidden quantum-well transitions were observed in bias-dependent electroreflectance spectra of In0.49Ga0.51P/In0.49(Al0.5Ga0.5)0.51P MQW samples with 10-nm-thick layers. We find the magnitude of these shifts to depend on the details of the Mg doping profile, confirming the importance of Mg diffusion and unintentional background doping in these materials. Our results show that (InAlGa)P materials are promising for visible-wavelength electro-optic modulator applications.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.111767
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  • 10
    Digitale Medien
    Digitale Medien
    Fabry–Perot reflectance modulator for 1.3 μm from (InAlGa)As materials grown at low temperature (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 919-921 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report the first all-semiconductor Fabry–Perot-cavity reflectance modulators operating at wavelengths of 1.32–1.33 μm. These devices were grown on a GaAs substrate using an intermediate, linearly graded InGaAs buffer layer terminating in an In0.33Ga0.67As layer. The Bragg reflector stacks of the Fabry–Perot structure are composed of InGaAs and InAlAs layers lattice matched to the buffer, and the active cavity region is an In0.4Ga0.6As/In0.26Al0.35Ga0.39As strained-layer superlattice. The key to obtaining device-quality material was low temperature growth (∼400 °C) of the entire structure. For a device with a 0.38-μm-thick active region and a 4 dB insertion loss, we obtained a contrast ratio of ∼3:1 at 4 V bias.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.108519
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