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  • 1
    Digitale Medien
    Digitale Medien
    Theoretical analysis and experimental study of Fourier transformation of Franz–Keldysh oscillations in GaAs (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 6429-6435 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Fourier transformation (FT) has been used in the theoretical line shape analysis of Franz–Keldysh oscillations (FKOs) in detail by numerical simulations. FKOs from the surface-intrinsic-n+ GaAs structure were obtained in photoreflectance (PR) measurements with various modulation light intensities and with different strengths of bias light illumination, which were used to change the static electric field in the intrinsic layer of the sample. The FT spectra of the PR spectra, including the real part, imaginary part, and the modulus, were very consistent with the theoretical line shapes. The ratio of the square root of the reduced mass (μL/μH) and the ratio of transition strength of the electron heavy hole to the electron light hole were obtained from the FT spectra. In addition, the electric field in the intrinsic layer of the sample without and with bias illumination and the modulation field induced by photomodulation were also obtained. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1319330
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  • 2
    Digitale Medien
    Digitale Medien
    Scanning force microscope and vacuum chamber for the study of ice films: Design and first results (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1781-1784 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: We present the design of a scanning force microscope and vacuum chamber for the growth and imaging of ice films in thermodynamic equilibrium and under controlled super or undersaturation. The apparatus allows measurements in the temperature range from −60 to +80 °C in a controlled water vapor atmosphere. First results on the morphology and the frictional properties of thin ice films on mica cleavage faces are presented. The films are found to grow in a two-dimensional manner, often exhibiting dendritic growth shapes. The lateral force measured on ice is higher than that observed on the surrounding substrate. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1148841
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  • 3
    Digitale Medien
    Digitale Medien
    Imaging and identification of atomic planes of cleaved Bi2Sr2CaCu2O8+δ by high resolution scanning tunneling microscopy (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 58-60 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Imaging of the surface of a cleaved Bi2Sr2CaCu2O8+δ (BSCCO) single crystal with a scanning tunneling microscope reveals a series of repeating terraces, whose separations are then used to identify the atomic planes which are exposed. On each of the exposed planes, the incommensurate modulation is also clearly resolved with atomic resolution. The measured separations between the terraces lead to the deduction that any atomic layer can be exposed by mechanical cleavage of BSCCO. We, therefore, suggest that the identity of atomic planes, and the direction of tunneling, should always be taken into consideration when interpreting tunneling spectra obtained on such cleaved BSCCO crystals. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.121722
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  • 4
    Digitale Medien
    Digitale Medien
    Photoreflectance of GaAs and Ga0.82Al0.18As at elevated temperatures up to 600 °C (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1080-1082 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report a modulation spectroscopy experiment on GaAs and Ga0.82Al0.18As at elevated temperatures. Using the contactless electromodulation method of photoreflectance, the direct gaps (E0) of these materials have been observed from 77 K to 600 °C. The latter temperature is comparable to molecular beam expitaxy, metalorganic chemical vapor deposition, growth temperatures, etc. Our results are at the highest temperature yet reported for E0 (GaAs) in a reflectance experiment and the first observation of E0 (Ga1−xAlxAs) at elevated temperatures. From the latter, the Varshni coefficients [Physica 34, 149 (1967)] for Ga0.82Al0.18As were determined.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.100027
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  • 5
    Digitale Medien
    Digitale Medien
    Dependence of the photoreflectance of semi-insulating GaAs on temperature and pump chopping frequency (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 2058-2060 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The amplitude of the photoreflectance (PR) spectra of the direct gap of semi-insulating GaAs has been studied as a function of pump chopping frequency (2–4000 Hz) and temperature (25–198 °C). We have been able to deduce a temperature-dependent trap time and hence trap activation energy of 0.70±0.05 eV. Our experiment demonstrates that PR can be used as a contactless method to study deep traps in semiconductors, analogous to deep level transient spectroscopy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.99580
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  • 6
    Digitale Medien
    Digitale Medien
    3He refrigerator based very low temperature scanning tunneling microscope (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 1459-1463 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: We describe the design and development of a scanning tunneling microscope (STM) which can operate at temperatures down to 240 mK and in magnetic fields up to 7 T with high spatial and energy resolution. The compact and rigid STM head is mounted directly on a low vibration, single shot, 3He refrigerator. This refrigerator can be operated at its base temperature continuously for several days before the 3He needs to be recondensed. The system is equipped with a sample transport manipulator from room temperature, and a cleavage device at low temperature, so that the cryogenic ultrahigh vacuum condition inside the cryostat can be utilized. A superconducting magnet provides a magnetic field of up to 7 T at the sample along the STM tip direction. Test results have shown that, at the base temperature, this instrument has better than 0.5 pm z-direction resolution in imaging mode, and better than 20 μV energy resolution in spectroscopy mode. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1149605
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  • 7
    Digitale Medien
    Digitale Medien
    Vacuum tunneling of superconducting quasiparticles from atomically sharp scanning tunneling microscope tips (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 2992-2994 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report on the study of atomically sharp superconducting tips for scanning tunneling microscopy and spectroscopy. The results clearly show vacuum tunneling of superconducting quasiparticles from atomically sharp tips. Observed deviations of the energy gap of the superconducting tip from its bulk value are attributed to the proximity effect. We show that a combination of a superconducting tip and an atomic resolution scanning tunneling microscope provides a means of achieving very high resolution local spectroscopy. We also discuss how this combination paves the way for a number of important applications. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.122654
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  • 8
    Digitale Medien
    Digitale Medien
    Annealing of intimate Au-GaAs Schottky barriers: Thick and ultrathin metal films (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 1247-1251 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Using valence-band and core-level photoemission spectroscopy (PES) and electrical device measurements, the effects of annealing on Au:n-type (110) GaAs Schottky diodes fabricated in ultrahigh vacuum have been studied. Similiar trends in the annealing-induced changes in the barrier height of Au:n-type GaAs were found for 0.2 and 15 monolayer coverages as determined by PES and for thick film coverages (1000 A(ring)) as determined by current-voltage (I-V) and capacitance-voltage (C-V) measurement techniques. In each case, the barrier height was found to be stable for temperatures between 30 and 200 °C and between 300 and 500 °C; while a gradual decrease in the barrier height was found for annealing temperatures of 200–300 °C. These changes are correlated with the formation of a Au-Ga rich layer at the interface during anneals at 200 to 300 °C. Leakage currents were found to dominate the I-V characteristics in the devices which were annealed above the Au-Ga eutectic temperature. These peripheral leakage currents were eliminated by mesa-etching the devices. This allowed more reliable barrier height determinations using device measurements for higher annealing temperatures than has been previously reported for the Au-GaAs system.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.334521
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  • 9
    Digitale Medien
    Digitale Medien
    EFFECT OF GERMINATION ON HEMAGGLUTINATING ACTIVITY OF PEA AND BEAN SEEDS (1977)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 42 (1977), S. 0 
    Details
    ISSN: 1750-3841
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The effect of germination on the blood hem agglutinating activity (BHA) of eight varieties’ of pea and bean seeds was studi Ed. Among seeds, the BHA of Wando, Laxton Progress, Pinto and soybean was the highest, that of Mung bean was the lowest. The BHA decreased progressively with days of germination. After 4 days of germination, the BHA of seeds decreased to the following percentages of ungerminated seeds: Dwarf Gray pea, 16.3%; Early Alaska pea, 8.1%; Laxton Progress pea, 5.3%; Mammoth Melting pea, 9.1%; Wando pea, 5.1%; and soybean, 3.7%. The BHA of Mung bean and Pinto bean disappeared completely after 4 days of germination. This study shows that an antinutritive factor, hemagglutinin, of seeds was decreased by germination.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2621.1977.tb08451.x
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  • 10
    Digitale Medien
    Digitale Medien
    Interplay of magnetism and high- T c superconductivity at individual Ni impurity atoms in Bi 2 Sr 2 CaCu 2 O 8+ δ (2001)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 411 (2001), S. 920-924 
    Details
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] Magnetic interactions and magnetic impurities are destructive to superconductivity in conventional superconductors. By contrast, in some unconventional macroscopic quantum systems (such as superfluid 3He and superconducting UGe2), the superconductivity (or ...
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1038/35082019
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