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  • Articles: DFG German National Licenses  (34)
  • Electronic Resource  (34)
  • 1995-1999  (34)
  • 1
    Electronic Resource
    Electronic Resource
    Field-ion scanning tunneling microscopy study of the atomic structure of 6H–SiC(0001) surfaces cleaned by in situ Si molecular beam etching (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 2524-2526 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Field ion-scanning tunneling microscopy has been used to study 6H–SiC(0001) surfaces with Si adlayers on the Si-terminated surface, formed by in situ Si molecular beam etching at 950 °C. The as-cleaned surface showed a ((square root of 3)×(square root of 3)) reconstruction. The (2×3), (2(square root of 3)×6(square root of)6), and (3×3) phases were formed by evaporating Si on this clean 6H–SiC(0001)-((square root of 3)×(square root of 3)) surface. A Si(111) film 6 monolayers thick was also epitaxially grown on the 6H–SiC(0001)-((square root of 3)×(square root of 3)) surface at 800 °C, and the surface exhibited the Si(111)–(7×7) reconstruction. A surface vacancy model for the ((square root of 3)×(square root of 3)) reconstruction is proposed, and a possible application of utilizing the various surface reconstructions to control the growth of different polytypes of SiC on the 6H–SiC substrate is discussed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363037
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Charge-exchange neutral particle measurements on electron cyclotron resonance heating experiments in hot-ion-mode plasmas of the GAMMA 10 tandem mirror : Proceedings of the 12th topical conference on high temperature plasma diagnostics (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 849-852 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Charge-exchange (C–X) neutral particle measurements have been carried out in hot-ion-mode plasmas of the GAMMA 10 tandem mirror. In the present experiment, a microwave power of 40 kW in 28 GHz is injected toward a second harmonic ECR layer located in the vicinity of the ICR layer at the central region and the radial profiles of ion temperatures determined from the energy spectrum of the C–X neutrals by using a neutral particle energy analyzer (NPA) are investigated from the viewpoint of ion energy balance. At the onset of the ECRH pulse, a remarkable increase of C–X neutral flux with high energy (few keV to few tens keV) is observed with NPA and the resultant ion temperature on the plasma axis is found to increase from 2.5 to 5.0 keV at the electron line density of 3×1013 cm−2. Based on the measured plasma parameters, radial profiles of ion-energy losses due to classical processes are evaluated and ECRH in the central region is confirmed to reduce the energy loss due to electron drag significantly in the core-plasma region. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149287
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  • 3
    Electronic Resource
    Electronic Resource
    Degradation mechanism of AlGaAs/GaAs laser diodes grown on Si substrates (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2995-2997 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the rapid degradation of the AlGaAs/GaAs single quantum well laser diodes on Si substrates grown by metalorganic chemical vapor deposition. The dislocations propagate at velocities up to ∼75 μm/h along 〈100〉 and ∼20 μm/h along 〈110〉, which cause an increase in threshold current and a decrease in differential quantum efficiency. The degraded current–voltage characteristic resulted from the defect-assisted impurity diffusion. The degradation process occurs very rapidly due to the presence of a high density of defects and thermally induced strain. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114930
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  • 4
    Electronic Resource
    Electronic Resource
    Atomic structure of faceted planes of three-dimensional InAs islands on GaAs(001) studied by scanning tunneling microscope (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 2265-2267 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The three-dimensional (3D) island structure was prepared by molecular beam epitaxy for the lattice mismatched InAs/GaAs(001) system and its images showing atomic structure on faceted planes were taken in situ by ultrahigh vacuum scanning tunneling microscopy (STM). The (113), (114), and (215) faceted planes are observed for the 3D islands. Based on the STM images, atomic structural models are proposed for the faceted surfaces. The surface structure of the (113) faceted planes we propose is different from those observed on the flat GaAs(113) surface. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121273
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of surface polarity on gallium adsorption on 6H-SiC surfaces (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 2776-2778 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have performed the first scanning tunneling microscopy (STM) study of gallium adsorption on both the Si-terminated 6H-SiC(0001) ((square root of 3)×(square root of 3)) and C-terminated 6H-SiC(0001¯) (2(square root of 3)×2(square root of 3)) surfaces. The structure of the Ga terminated 6H-SiC surface showed strong polarity dependence. On the Si-terminated (square root of 3)×(square root of 3) surface, parallel rows of Ga atoms arranged in three different domains oriented at 120° with respect to each other at 1 ML coverage were observed. On the C-terminated 2(square root of 3)×2(square root of 3) surface, sets of two concentric rings formed an overall 4(square root of 3)×4(square root of 3) reconstruction at 1 ML coverage. We propose a structural model for the 4(square root of 3)×4(square root of 3) structure which explains the STM image. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120130
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  • 6
    Electronic Resource
    Electronic Resource
    Two-step preparation of 6H–SiC(0001) surface for epitaxial growth of GaN thin film (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 2468-2470 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A scratch-free and atomically flat 6H–SiC(0001) surface has been successfully prepared by a two-step method which combines atmospheric hydrogen treatment and ultrahigh vacuum Si etching. On this surface, a high-quality GaN(0001) thin film is obtained by radio frequency nitrogen plasma assisted molecular beam epitaxy. Its surface exhibits a typical terrace-plus-step morphology, which enables us to study various GaN(0001) surface superstructures and hollow-core defects with atomic resolution by scanning tunneling microscopy. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123883
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  • 7
    Electronic Resource
    Electronic Resource
    AlGaAs/GaAs light-emitting diode on a Si substrate with a self-formed GaAs islands active region grown by droplet epitaxy (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 523-525 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the preliminary results on self-formed GaAs islands grown on the GaAs/Si substrate by metalorganic chemical vapor deposition using droplet epitaxy. Atomic force microscope observation shows that the GaAs islands exhibit a conical shape with heights of 90–170 nm, diameters of 600–750 nm, and densities of 107 cm−2, which are controlled by the trimethylgallium flow rate. In addition, an AlGaAs/GaAs light-emitting diode (LED) on Si with a self-formed GaAs island active region was fabricated by the use of this technique. The LED was operated up to 27 μW at 190 mA under direct current conditions at room temperature. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116387
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  • 8
    Electronic Resource
    Electronic Resource
    Erasable nanometer-scale modification at the Au/Si interface by ballistic electron emission microscopy (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 3668-3670 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report that local modification and its erasing with a nanometer-scale size can be performed at a Au/Si(111) interface using ballistic electron emission microscopy (BEEM). By applying a negative voltage on the tip, a region was created where no BEEM current flows at the interface and was imaged with BEEM. The modified area can be erased by applying a voltage with the opposite polarity. It is found that the minimum size of writing and erasing corresponds to Au grains, suggesting a method of rewritable memory on a nanometer-scale dimension. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125423
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  • 9
    Electronic Resource
    Electronic Resource
    Transmission-type X-ray linear polarizer with perfect crystals (1998)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 5 (1998), S. 738-740 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Even though conventional X-ray polarizers with multiple-reflection channel-cut structures perform well, they suffer from the disadvantage that the polarized beam is non-stationary as the energy is scanned. In this paper the possibility of using a thin Bragg reflector as a polarizing filter is investigated, so that the transmitted beam (rather than the Bragg-reflected beam) is used. Consequently, the position and direction of the transmitted beam are unchanged as the energy is changed, or even when the polarization direction to be filtered out is changed. Theoretical considerations as well as experimental results on the performance characteristics of the proposed transmission-type X-ray linear polarizer are presented. A polarization ratio, defined as IH/IV, higher than 105 was obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0909049597019560
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  • 10
    Electronic Resource
    Electronic Resource
    Tunable X-ray polarization reflector with perfect crystals (1999)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 955-962 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The possibility of a transmission-type X-ray linear polarizer is investigated using a thin Bragg reflector as a polarizing filter. In this device, the transmitted beam (rather than the Bragg-reflected beam) is the useful output of the device. Consequently, the position and the direction of the transmitted beam are unchanged as the energy is changed, or even when the polarization direction to be filtered out is changed. Theoretical considerations as well as preliminary transmissivity measurements are presented. The use of perfect crystals of silicon and diamond is examined. A polarization ratio, defined as I_H/I_V, higher than 105 was observed in experiments to measure the performance characteristics of the proposed X-ray polarizing reflector. The transmission-type X-ray linear polarizer is well suited for spectroscopic measurements with polarized X-rays.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767399007138
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