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  • 1
    Electronic Resource
    Electronic Resource
    Determination of the local Al concentration in AlxGa1−xAs-GaAs quantum well structures using the (200) diffraction intensity obtained with a 10 A(ring) electron beam (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1454-1456 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A novel method for determining the local concentration of Al in the AlxGa1−xAs layer of AlxGa1−xAs-GaAs multiple quantum well structures is reported. By scanning a 10 A(ring) electron beam across the interface, the (200) dark-field scanning transmission electron microscopy (STEM) image shows the contrast of the AlxGa1−xAs-GaAs multilayer since the intensity of the (200) diffraction is sensitive to the Al concentration. The line scan intensity profile of the (200) diffraction, along a uniform specimen region of known thickness, shows the intensity variation of the (200) diffraction and reflects the local content of Al in each region. The simulation of the nanodiffraction patterns produces a chart of the (200) diffraction intensity versus the Al concentration for the determination of the local change of the Al concentration. A molecular beam epitaxy grown AlxGa1−xAs-GaAs specimen (x=0.57 as determined from Raman spectroscopy) is tested and the dark-field STEM studies show two thin layers of x=0.46 at the 1/3 and 2/3 height level within every AlxGa1−xAs layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100695
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  • 2
    Electronic Resource
    Electronic Resource
    Investigations of Rh-based multilayers for soft x-ray applications by high-resolution electron microscopy (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 2905-2910 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A series of rhodium-based multilayer structures has been developed for soft x-ray applications by using "trilayer'' structures and low density boron carbide spacing material. The microstructure of the multilayers was investigated by high-resolution electron microscopy and compared with those of tungsten- and nickel-based multilayers. Rh crystals having fcc structure but with different preferred orientations were identified in Rh-based layers. It was confirmed that the major limitation on the performance of the multilayer materials was the crystallization of the metal layers. High reflectivity and selectivity for x-ray mirrors was obtained in the case of W/Rh/C multilayers due to significant improvement in their microstructure, especially the interface roughness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349314
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  • 3
    Electronic Resource
    Electronic Resource
    Raman scattering by interface phonons in GaAs-AlAs multiple-quantum-well structures: Correlation between Raman and high-resolution electron microscopy results (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 418-421 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of shallow impurity and interface roughness on resonant Raman scattering by interface phonons in GaAs-AlAs multiple quantum-well structures have been studied. By correlating the Raman results with observations by high-resolution electron microscopy, it has been demonstrated that Raman scattering from interface phonons depends strongly on the sample quality. For a relatively smooth interface with about 1–2 monolayers of interface roughness, the Raman signal is governed primarily by the impurity if the impurity concentration inside the GaAs layers is greater than about 2×1016 cm−3. On the other hand, for nominally undoped quantum-well structures, the Raman signal can be dominated by interface roughness if the interfaces are sufficiently distorted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350291
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  • 4
    Electronic Resource
    Electronic Resource
    Microstructural study of Mg-doped p-type GaN: Correlation between high-resolution electron microscopy and Raman spectroscopy (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 6008-6011 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A series of Mg-doped GaN films (∼1–1.3 μm) grown by reactive molecular beam epitaxy at substrate temperatures of 750 and 800 °C has been studied by high-resolution electron microscopy (HREM) and Raman spectroscopy. Stacking defects parallel to the substrate surface were observed in samples grown on sapphire substrates at 750 °C with AlN buffer layers (60–70 nm) at low Mg concentration. A transition region with mixed zinc-blende cubic (c) and wurtzite hexagonal (h) phases having the relative orientations of (111)c//(00.1)h and (11¯0)c//(10.0)h was observed for increased Mg concentration. The top surfaces of highly doped samples were rough and assumed a completely zinc-blende phase with some inclined stacking faults. Samples grown with a Mg cell temperature of 350 °C and high doping levels were highly disordered with many small crystals having inclined stacking faults, microtwins, and defective wurtzite and zinc-blende phases. Correlation between HREM and Raman scattering results points towards the presence of compressive lattice distortion along the growth direction which might be attributable to structural defects. The films grown at 800 °C had better quality with less observable defects and less yellow luminescence than samples grown at 750 °C. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366466
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  • 5
    Electronic Resource
    Electronic Resource
    Structural properties of GaN films grown on sapphire by molecular beam epitaxy (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 1141-1143 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structural characteristics of GaN films grown on sapphire substrates by molecular beam epitaxy have been investigated using high-resolution synchrotron x-ray diffraction and electron microscopy. We find remarkable correspondence between the in-plane structural order (coherence length and mosaic spread) and the electrical and optical properties. Contrary to common belief, our observations show unequivocally that the out-of-plane structural features, which are considerably better developed than the in-plane counterparts, cannot be used for determining the material quality with respect to their optical and electrical activity. In particular, the (00l) mosaic spread is not a good indicator of film quality. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115739
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  • 6
    Electronic Resource
    Electronic Resource
    Growth and characterization of heteroepitaxial CdTe and ZnTe on Ge(001) buffer layers (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 2086-2088 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The microstructure of heteroepitaxial CdTe (001) and ZnTe(001) epilayers grown on Ge(001) buffer layers by molecular beam epitaxy has been characterized using electron microscopy. Apart from occasional {111} stacking faults originating at the interfacial region, the prevailing defects present in both systems are identified by high-resolution imaging as perfect Lomer edge dislocations with Burgers vectors of the type a/2〈110〉 parallel to the interface plane, which are indicative of well-relaxed material. Double-crystal rocking-curve measurements using Ge(001) buffer layers give full-width-at-half-maximum values of 210 arc-sec for a 7.5μm thick ZnTe film and 125 arc-sec for a 12μm thick CdTe film. Use of the Ge buffer layers on Si(001) substrates represents a valuable precursor for eventual growth of mercury cadmium telluride since this allows the substrate orientation to be maintained. The buffer layer also permits a substantial reduction of the in situ annealing temperature needed for substrate oxide removal. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116888
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  • 7
    Electronic Resource
    Electronic Resource
    Microstructure of heteroepitaxial CdTe grown on misoriented Si(001) substrates (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 1591-1593 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transmission electron microscopy has been used to characterize the microstructure of heteroepitaxial CdTe (111) layers grown by molecular beam epitaxy directly on nominal and misoriented Si(001) substrates. High-resolution electron micrographs showing atomic-scale details of the CdTe (111)/Si(001) interface have been recorded. Layer quality depended on the substrate tilt parameters, including the offcut orientation angle θ, and the azimuthal angle φ relative to [110]. Small φ values (4° and 10°) gave high densities of stacking fault twins throughout the epilayer whereas larger misorientation angles led to a rapid falloff away from the substrate. Under optimized growth conditions, the occurrence of twins effectively dropped to zero within a distance of less than 2.5 μm from the substrate surface. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114949
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