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  • 1
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 51-52 (May 1996), p. 283-288 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 196-201 (Nov. 1995), p. 1847-1852 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 207-209 (Feb. 1996), p. 757-760 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Strained GaSb quantum dots having a staggered band lineup (type II) are formed in a GaAs matrix using molecular beam epitaxy. The dots are growing in a self-organized way on a GaAs(100) surface upon deposition of 1.2 nm GaSb followed by a GaAs cap layer. Plan-view transmission electron microscopy studies reveal well developed rectangular-shaped GaSb islands with a lateral extension of ∼20 nm. Intense photoluminescence (PL) is observed at an energy lower than the GaSb wetting layer luminescence. This line is attributed to radiative recombination of 0D holes located in the GaSb dots and electrons located in the surrounding regions. The GaSb quantum dot PL dominates the spectrum up to high excitation densities and up to room temperature. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-2746
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract 400 kV high resolution electron microscopy (HREM), deep level transient spectroscopy (DLTS) and steady state electrical measurements have been applied to ∑37(610) and ∑29(520) [001] tilt grain boundaries (GBs) in germanium bicrystals. The atomic boundary structures were revealed by experimental HREM images taken under different defocus conditions. Later, structure models were refined by means of a trial-and-error method applying alternatively the image simulation and the molecular static calculation of relaxed structures. The structures were shown to be consistent with the modified structural unit model. Although the structures are different for the two GBs studied, DLTS data and steady state measurements were found to be quite similar for both GBs. Thus, the results point to the extrinsic origin of localized deep states at the GBs. The analysis of DLTS spectra indicates the impurity segregation at the boundary, e.g., the formation of vacancy-type oxygen complexes of a donor-like state at E c-0.21 eV, which results in the fluctuation of the potential barrier. Defects in the GBs—like facets, atomic steps and secondary grain boundary dislocations—which are characteristic of both boundaries can act as nuclei to the impurity segregation.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-2746
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The thin-film spinel-forming solid state reaction between Al2O3 and MgO has been studied under initially non-coherent conditions. MgO films in (001) orientation on $$(1\bar 1.2)$$ -cut sapphire single crystals were heated at 1100°C for 30 min or 1h. The film/substrate reaction proceeds via cation counterdiffusion as was revealed by a marker experiment. The MgAl2O4 films formed were predominantly (001) oriented, with an additional systematic tilt of about 5° of the spinel lattice around the [010] axis. The structure of the Al2O3 $$(1\bar 1.2)$$ /MgAl2O4(001) and MgAl2O4(001)/MgO(001) reaction fronts has been investigated on cross section samples by high-resolution electron microscopy. It appeared that after starting from an incoherent interface, the Al2O3 $$(1\bar 1.2)$$ /MgAl2O4(001) front assumes an almost fully coherent structure during the reaction. As a result the lattice misfit is reduced to 1%, and interfacial ledges are formed. The latter most probably play an active role in the necessary c.p.h. → f.c.c. reconstruction of the oxygen sublattice. The MgAl2O4(001)/MgO(001) reaction front consists of coherent regions divided by misfit dislocations. During the reaction the former run ahead whereas the latter lag behind. As a result the morphology of the reaction front is bowed. The results confirm earlier observations of Carter and Schmalzried of the semicoherent Al2O3(00.1)/CoAl2O4(111) interface, thus strongly supporting the conclusion of a fundamental new phase transformation mechanism specific to oxide systems.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0044-2313
    Keywords: Solid state reactions ; spinel-forming reactions ; MgAl2O4 thin films ; transmission electron microscopy ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: TEM-Untersuchungen von Spinellbildungsreaktionen: Reaktionsmechanismus, Schichtorientierung und Grenzflächenstruktur bei der MgAl2O4-Bildung auf (001) MgO- und (1 1.2) Al2O3-EinkristallsubstratenEs wird über experimentelle Untersuchungen der Bildung wohlorientierter MgAl2O4-Spinellschichten durch Festkörperreaktion zwischen (I) einem (001) MgO-Substrat und Al2O3-Dampf sowie (II) einem (1 1.2) Al2O3-Substrat und einer abgeschiedenen MgO-Schicht berichtet. Zusammensetzung, Struktur und Morphologie der Schichten werden durch XRD, SEM, TEM/SAED und EDX charakterisiert. Die beteiligten Reaktionsfronten werden mit Hilfe der hochauflösenden Transmissionselektronenmikroskopie atomarer Auflösung (ARM) an Querschnittsproben untersucht. Die Richtung des Gesamtdiffusionsstromes und die Art der diffundierenden Teilchen werden experimentell unter Zuhilfenahme inerter Markierungen submikroskopischer Abmessung bestimmt. Die Fälle (I) und (II) weisen gemeinsame Merkmale, aber auch wesentliche Unterschiede auf. Auf (001) MgO-Substraten wachsen die MgAl2O4-Schichten in der einfachen kubischen Orientierungsbeziehung MgAl2O4(001) ∥ MgO(001); MgAl2O4[100] ∥ MgO[100]. Die Schichten bestehen aus kleinen Körnern von ca. 25 bis 50 nm Durchmesser, deren Orientierungen um Winkel bis zu etwa ± 2° symmetrisch um die exakte Orientierung verteilt sind. Auf (1 1.2) Saphirsubstraten wachsen die MgAl2O4-Schichten annähernd in der Orientierung MgAl2O4(001) ∥ Al2O3(1 1.2); MgAl2O4[010] ∥ Al2O3[11.0]. Diese Schichten bestehen aus größeren Körnern von ca. 100 nm Durchmesser, deren Orientierungen systematisch von der obigen Orientierung abweichen, und zwar durch einseitige Rotation von bis zu 5 bis 6° um die [11.0]-Achse des Substrats. Die Struktur der jeweiligen Reaktionsfronten zeigt charakteristische Unterschiede, die mit diesen Beobachtungen korrespondieren und die mit Blick auf unterschiedliche Mechanismen im Anfangsstadium der Spinellbildungsreaktion diskutiert werden, wobei letztere eine Folge der unterschiedlichen kristallographischen Randbedingungen zu Beginn der Reaktion sind.
    Notes: The formation of well-oriented MgAl2O4 spinel films by solid state reactions between (i) a MgO (001) substrate and an Al2O3 vapour and (ii) a sapphire (1 1.2) substrate and a deposited solid MgO film, respectively, is experimentally investigated. Composition, structure and morphology of the films are characterized by XRD, SEM, TEM/SAED, and EDX. The reaction fronts involved are investigated by cross-sectional atomic resolution transmission electron microscopy (ARM). The direction of the overall diffusion flux and the kind of diffusing species are determined in experiments using inert markers of sub-micron size. There are common features and, however, distinct differences between cases (i) and (ii). On MgO (001) substrates, the MgAl2O4 films grow in a simple cube-to-cube orientation: MgAl2O4(001) ∥ MgO(001); MgAl2O4[100] ∥ MgO [100]. The films consist of small grains about 25 to 50 nm in diameter, the orientation of which is symmetrically distributed around the exact orientation, with maximum deviations of about ±2°. On sapphire (1 1.2) substrates the MgAl2O4 films grow almost in the orientation MgAl2O4(001) ∥ Al2O3(1 1.2); MgAl2O4[010] ∥ Al2O3[11.0]. These films consist of larger grains about 100 nm in diameter, the orientation of which systematically deviates from the above orientation by unidirectional rotations up to 5 to 6° around the substrate [11.0] axis. The structures of the reaction fronts show corresponding differences, which are discussed in terms of different mechanisms occurring at the initial stage of the spinelforming reaction because of the different crystallographic conditions at the beginning of the reactions.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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