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Demonstrates that the presence of low-temperature-grown GaAs in LT-GaAs/AlAs/GaAs:Si heterostructures increase the Al/Ga interdiffusion at the heterostructure interfaces. Causes of the interdiffusion enhancement.

Presents a study that investigated homoepitaxial deposition of a GaN overlayer onto a bulk single-crystal GaN substrate using molecular beam epitaxy. Comparison of structural quality of deposited GaN overlayer with heteroepitaxially grown layers; Photoluminescence of bulk GaN and the deposited homoepitaxial GaN layer; Benefits for the development of benchmark values for the optoelectronic properties of GaN thin films.

The effect of secondary sintering additives and/or a post-sintering heat treatment on the semicrystalline atomic structure of the intergranular phase in silicon nitride ceramics is investigated. Three different Yb-doped Si3N4 ceramic compositions are examined using a scanning transmission electron microscope, whereby the intergranular atomic structure is directly imaged with Ångstrom resolution. The resulting high-resolution images show that the atomic arrangement of the Yb takes very periodic positions along the interface between the intergranular phase and the matrix grains, and that a postsintering 1250 °C heat treatment, as well as a change of the secondary sintering additives (Al2O3 vs SiO2), does not alter the atomic positions of Yb. This result has implications for the understanding of how the mechanical properties of ceramics are influenced by the presence of the nanoscale intergranular phase, and for associated computational modeling of its precise role and atomic structure. [ABSTRACT FROM AUTHOR]

Hexagonal InN layers were grown by molecular beam epitaxy and studied by high resolution electron microscopy and by photoluminescence spectroscopy. Inclusions of a few nanometers in diameter were found, which are among the smallest reported. Image simulation, beam sensitivity, and photoluminescence of the samples corroborate that these inclusions are indeed metallic indium. This letter provides evidence that nanoscopic metallic indium inclusions can be present in InN crystals and have a strong influence on its optical properties. [ABSTRACT FROM AUTHOR]

The structure and the interface chemistry of epitaxial BiFeO3–NiFe2O4 nanocomposite thin films on SrTiO3(001) substrates were investigated using the Z-contrast imaging and the electron exit-wave reconstruction methods at the atomic scale. The results show that the NiFe2O4 pillars are nonwetting with respect to the substrate and exhibit {111} facets at the surface. The interface between BiFeO3 and NiFe2O4 lies in the {110} planes and is semicoherent. The atomic configuration of the interface, with the BiFeO layer bonding to the [Ni,Fe]O2 layer, was shown to have the maximized structure continuity and minimized interface charging. [ABSTRACT FROM AUTHOR]

Employing the focal-series reconstruction technique in high-resolution transmission electron microscopy, we obtained true atomic resolution images of interfacial disorder within cation and anion sublattices across interfaces in an InGaSb/InAs heterostructure. This enabled independent quantitative mapping of changes in the In–Ga and As–Sb contents across interfacial regions ∼0.6 nm in width. A comparison of the cation and anion sublattice images revealed that intermixing at the InGaSb-on-InAs interface is confined to the In–Ga sublattice. Also, atomic scale roughness within the As–Sb sublattice of the InAs-on-InGaSb interface was discerned. This approach is general, permitting atomic-scale compositional analysis of heterointerfaces with two species per sublattice. [ABSTRACT FROM AUTHOR]

Nanoscale intergranular films in doped silicon-nitride ceramics are known to markedly affect toughness and creep resistance. They are regarded as being fully amorphous, but are shown here to have a semicrystalline structure in a Ce-doped Si3N4. Using two different but complementary high-resolution electron-microscopy methods, the intergranular atomic structure, imaged with sub-angstrom resolution, reveals that segregated cerium ions take very periodic positions, along the intergranular-phase/matrix-grain interface and as a semicrystalline structure spanning the width of the intergranular phase. This result has broad implications for the understanding of the structure and role of the intergranular phase in enhancing the mechanical properties of ceramics. [ABSTRACT FROM AUTHOR]

InN thin films have been grown epitaxially on GaN-buffered sapphire substrates by molecular-beam epitaxy at 500 °C. A high level of oxygen contamination in the growth chamber led to formation of In2O3 precipitates in the films. These precipitates were characterized in detail by transmission electron microscopy (TEM). The concentration of In2O3 was estimated to be less than 0.07 vol % in the present samples of oxygen content ∼0.5 at. %. Cross-sectional TEM investigations revealed that the precipitates adopt a preferred crystallographic orientation within the InN matrix, and show a characteristic diameter of ∼5 nm with average distance of ∼500 nm. These observations suggest the effective solubility of O in InN could be below 1 at. % at 500 °C. [ABSTRACT FROM AUTHOR]

Single-crystal GaN thin films have been deposited epitaxially on a HfN-buffered Si(111) substrates by molecular-beam epitaxy. The microstructural and compositional characteristics of the films were studied in detail by transmission electron microscopy (TEMs). Cross-sectional TEM investigations have revealed the crystallographic orientation relationship in different GaN/HfN/Si layers. GaN film polarity is studied by conventional TEM and convergent beam electron diffraction simulations, and the results show that the GaN film has a Ga polarity with relatively high density of inversion domains. Based on our observations, growth mechanisms related to the structural properties are discussed. [ABSTRACT FROM AUTHOR]

A letter is presented in response to the article "Three-dimensional atom probe studies of an In(sub x)Ga(sub 1-x)N/GaN multiple quantum well structure: Assessment of possible indium clustering," which appeared in issue no. 90 of 2007.