Search results for "electron diffraction"
showing 10 items of 191 documents
A new microporous 12-ring zincosilicate THK-2 with many terminal silanols characterized by automated electron diffraction tomography.
2020
A newly synthesized microporous zincosilicate THK-2 (estimated structural composition: |(H2O)6.7(C6H13N)0.9|[Li0.5Zn3.1Si32O62.7(OH)9.3]) was characterized by single-crystal electron diffraction using the automated electron diffraction tomography (ADT) approach in combination with powder X-ray diffraction. The lattice constants and space group of as-synthesized THK-2 were a = 2.50377(7) nm, b = 1.43866(4) nm, c = 0.505369(8) nm, and Pccn (no. 56) with orthorhombic symmetry. Because the crystal lattice was almost identical to a hexagonal lattice (), the first several peaks in its powder X-ray diffraction data severely overlapped, which suppressed the structural information to decide the fram…
Anisotropic chemical etching of semipolar \{10\bar {1}\bar {1}\}\mbox {/} \{10\bar {1}{+}1\} ZnO crystallographic planes: polarity versus dangling bo…
2009
ZnO thin films grown by metal?organic vapor phase epitaxy along the nonpolar direction and exhibiting semipolar facets have been chemically etched with HCl. In order to get an insight into the influence of the ZnO wurtzite structure in the chemical reactivity of the material, Kelvin probe microscopy and convergent beam electron diffraction have been employed to unambiguously determine the absolute polarity of the facets, showing that facets are unstable upon etching in an HCl solution and transform into planes. In contrast, facets undergo homogeneous chemical etching perpendicular to the initial crystallographic plane. The observed etching behavior has been explained in terms of surface oxy…
Änderungen der Gitterstruktur hochpolymerer Einkristalle durch Bestrahlung im Elektronenmikroskop
1965
Die durch Bestrahlung mit Elektronen von 40 bis 80 kV hervorgerufenen Anderungen der Gitterstruktur von Polyathylen(PA)- und Polyoxymethylen(POM)-Einkristallen wurden unterrsucht. Dazu wurden Lage, Intensitat und Linienbreite der Reflexe im Elektronenbeugungsdiagramm in Abhangigkeit von der Bestrahlungsdosis gemessen. Vergleichende Untersuchungen wurden an einem Paraffin (C28H58) durchgefuhrt. Aus den Anderungen der Linienbreite konnte geschlossen werden, das im Falle des PA durch die Vernetzung zwischen benachbarten Ketten Gitterstorungen II. Art (parakristalline Storungen) hervorgerufen werden. Sie fuhren auch zu einer betrachtlichen Aufewitung des Gitters. Im Falle des Paraffins dagegen …
Structure and electronic properties of ultrathin Co films on W(110)
2004
Abstract The structure and electronic properties of ultrathin Co films on W(1 1 0) grown by molecular beam epitaxy in UHV were investigated by low energy electron diffraction (LEED) and scanning tunneling microscopy and spectroscopy (STM and STS). For coverages above 0.7 ML the pseudomorphic (ps) monolayer is transformed gradually into close-packed (cp-) monolayer areas, showing up as separated islands that increase in size with coverage until the cp-monolayer is complete. Two different structures of the cp-monolayer were observed by atomically resolved STM, both leading to a 8 × 1 superstructure in the LEED pattern. Higher coverages continue to grow in the Stransky–Krastanov growth mode fo…
Synthesis of yttrium aluminum garnet nanoparticles in confined environment II: Role of the thermal treatment on the composition and microstructural e…
2017
Abstract Nanoparticles of yttrium aluminum garnet (YAG, Y 3 Al 5 O 12 ) have been obtained by thermal treatments, at several temperature in the range 400–950 °C, of the precursors synthetized via co-precipitation in water in oil microemulsion. The obtained nanoparticles have been characterized by means of X-ray Diffraction and Transmission Electron Microscopy coupled with Energy Dispersive X-ray Spectroscopy (EDS) and Select Area Electron Diffraction (SAED). Results show the phase evolution occurring to obtain not aggregated nanoparticles of YAG phase. A possible growth mechanism of YAG nanoparticles is discussed on the basis of observed particle microstructure and morphology. The results i…
Crystal chemical characterization of mullite-type aluminum borate compounds
2017
Abstract Al-rich aluminum borates were prepared by different synthesis routes using various Al/B ratios, characterized by diffraction methods, spectroscopy and prompt gamma activation analysis. The 11B NMR data show a small amount of BO4 species in all samples. The chemical analysis indicates a trend in the Al/B ratio instead of a fixed composition. Both methods indicate a solid solution Al5−xB1+xO9 where Al is substituted by B in the range of 1–3%. The structure of B-rich Al4B2O9 (C2/m, a=1488 pm, b=553 pm, c=1502 pm, s=90.6°), was re-investigated by electron diffraction methods, showing that structural details vary within a crystallite. In most of the domains the atoms are orderly distrib…
Epitaxial Mn2Au thin films for antiferromagnetic spintronics
2015
Mn2Au is one of the few candidate materials for antiferromagnetic spintronics requiring ordered metals with a high Neel-temperature and strong spin–orbit coupling. We report the preparation of epitaxial Mn2Au thin films by rf-sputtering. Structural characterization by x-ray and electron diffraction demonstrates a high degree of atomic order and the temperature dependence of the resistivity is typical for a good metal. The magnetic properties of the samples are studied by the investigation of Mn2Au/Fe bilayers. Exchange bias effects are observed, which present strong evidence for antiferromagnetic order in the Mn2Au thin films. Small domains of 500 nm are visualized in the exchange coupled F…
Heusler compounds as ternary intermetallic nanoparticles: Co2FeGa
2009
This work describes the preparation of ternary nanoparticles based on the Heusler compound Co2FeGa. Nanoparticles with sizes of about 20?nm were synthesized by reducing a methanol impregnated mixture of CoCl2 ? 6H2O, Fe(NO3)3 ? 9H2O and Ga(NO3)3 ? xH2O after loading on fumed silica. The dried samples were heated under pure H2 gas at 900??C. The obtained nanoparticles?embedded in silica?were investigated by means of x-ray diffraction (XRD), transmission electron microscopy, temperature dependent magnetometry and M??bauer spectroscopy. All methods clearly revealed the Heusler-type L21 structure of the nanoparticles. In particular, anomalous XRD data demonstrate the correct composition in addi…
Experimental and theoretical evidence for substitutional molybdenum atoms in theTiO2(110)subsurface
2006
Molybdenum was deposited at room temperature on the ${\mathrm{TiO}}_{2}(110)$ surface in the 0--1.3 equivalent monolayer (eqML) range and was then annealed at $400\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ in order to reach a kind of equilibrium state. A threshold was found in the behavior of the deposit: below 0.2 eqML, substitutional molybdenum occurs in titanium sites located under the bridging oxygen atoms of the ${\mathrm{TiO}}_{2}(110)$ surface. In this position, molybdenum atoms are in a structural and chemical ${\mathrm{MoO}}_{2}$-like environment. Density-functional theory calculations show that this molybdenum site is actually the most stable one in …
Structural and electronic properties ofβ-FeSi2nanoparticles: The role of stacking fault domains
2014
We use conventional and aberration-corrected transmission electron microscopy (TEM) and ab initio calculations to investigate the structural and electronic properties of \ensuremath{\beta}-FeSi${}_{2}$ nanoparticles, which are a promising material for photovoltaic applications due to a band gap of 1 eV and a high absorption coefficient. The nanoparticles have average sizes of \ensuremath{\sim}20 nm, form aggregates, and are prepared by gas-phase synthesis. Amorphous SiO${}_{x}$ shells with thicknesses of \ensuremath{\sim}1.7 nm around \ensuremath{\beta}-FeSi${}_{2}$ cores are identified on individual nanoparticles using electron energy-loss spectroscopy, while stacking fault domains in the …