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HRTEM Images (hrtem + image)

Distribution by Scientific Domains
Chemistry66%
Polymers and Materials Science33%

Selected Abstracts

Influence of Mg Doping on GaN Nanowires

CHEMPHYSCHEM, Issue 3 2009
Dongdong Zhang
Abstract Magnesium-doped GaN nanowires with different dopant concentrations are synthesized and their morphology, structure, growth properties, crystallinity, and optical properties investigated. The nanowires are single-crystalline with hexagonal wurzite structure, and doping with 5 atom,% of Mg gives nanowires with the best morphology and crystallinity (see HRTEM image). Magnesium-doped GaN nanowires with different dopant concentrations are synthesized by ammoniating Ga2O3 thin films doped with Mg at 900,°C. Scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), high-resolution transmission electron microscopy (HRTEM), and room-temperature photoluminescence (PL) are employed to characterize the influences on the morphology, structure, crystallinity, and optical properties of Mg-doped GaN nanowires. The results demonstrate that the nanowires are single-crystalline with hexagonal wurzite structure. GaN nanowires doped with 5 atom,% of Mg have the best morphology and crystallinity with a single-crystalline structure, and at this composition the PL spectrum with the strongest UV peak is observed. The growth mechanism of crystalline GaN nanowires is discussed briefly. [source]

The Oriented Self-Assembly of Magnetic Fe3O4 Nanoparticles into Monodisperse Microspheres and Their Use as Substrates in the Formation of Fe3O4 Nanorods

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 3 2008
Guangcheng Xi
Abstract We describe a facile solvothermal route for the large-scale preparation of ferromagnetic Fe3O4 sub-micrometer spheres and nanorods by using FeCl3 as the iron source, oleic acid as the surfactant, and ethylene glycol as the reducing agent and solvent. The as-synthesized Fe3O4 microspheres are composed of a mess of Fe3O4 nanoparticles with a size of 10 nm and have nearly monodisperse diameters that can be controlled in the range 100,410 nm. HRTEM images and SAED patterns show that these microspheres present a "single-crystalline" nature, which can be attributed to the highly oriented assembly of the small Fe3O4 nanoparticles. Interestingly, by using the pre-synthesized Fe3O4 microspheres as the growth substrate, single-crystalline Fe3O4 nanorods can be formed on the surfaces of the microspheres. These nanorods are about 7,20 nm in diameter and 120,400 nm in length, and have smooth surfaces. The formation mechanisms of the Fe3O4 microspheres and nanorods have been investigated and discussed. Furthermore, the magnetic properties of the as-synthesized microspheres and nanorods have also been investigated and the magnetization saturation values are 74.6 and 92.3 emu/g, respectively.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

Transmission Electron Microscopy and UV,vis,IR Spectroscopy Analysis of the Diameter Sorting of Carbon Nanotubes by Gradient Density Ultracentrifugation

ADVANCED FUNCTIONAL MATERIALS, Issue 14 2009
Romain Fleurier
Abstract Diameter separation of single-walled carbon nanotubes is achieved via the density gradient ultracentrifugation process. Statistical analysis of the separated samples is performed using high-resolution transmission electron microscopy (HRTEM). The evolution of the diameter distribution with respect to the gradient density is extracted by analyzing hundreds of HRTEM images, and the results are found to be consistent with those estimated by UV,vis,IR spectroscopy. The efficiency of the separation process can be quantitatively characterized by the standard deviation of the diameter distribution, which is determined from the TEM analyses. This particular study indicated that for electric arc nanotubes dispersed in sodium cholate, diameter sorting is more efficient in the upper part of the gradient. [source]

Diffusion of Adhesion Layer Metals Controls Nanoscale Memristive Switching

ADVANCED MATERIALS, Issue 36 2010
J. Joshua Yang
Thermal diffusion of Ti through Pt electrode forms Ti atom channels of 1 nm diameter along Pt grain boundaries, seeding switching centers and controlling nanoscale memristive switching. The image shows EFTEM maps of Ti overlaid on HRTEM images for a Si/SiO2 100 nm/Ti 5nm/Pt 15 nm sample in-situ annealed in ultrahigh vacuum at 250 °C for 1 hour. [source]

Octahedral tilt twinning and compositional modulation in NaLaMgWO6

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 6 2009
Graham King
A combination of selected-area electron diffraction (SAED), neutron powder diffraction (NPD) and high-resolution transmission electron microscopy (HRTEM) reveals a complex superstructure in the ordered perovskite NaLaMgWO6. Through indexing of SAED patterns the unit-cell dimensions are found to be 46.8 × 7.8 × 7.9,Å, which corresponds to a 12ap× 2ap× 2ap superstructure of the simple perovskite unit cell. HRTEM images reveal the formation of an unmistakable stripe contrast that repeats with the same periodicity. Doubling of the b and c axes is brought about by a combination of layered ordering of Na and La, rock-salt ordering of Mg and W, and octahedral tilting. The a axis repeat distance results from a one-dimensional twinning of the octahedral tilts in combination with a compositional modulation. Modeling of the NPD pattern shows that the underlying tilt system is a,a,c0 with tilt angles of ,,8° about the a and b axes. The octahedral tilt-twin boundaries run perpendicular to the a axis and are separated by 6ap. Simulated HRTEM images show that octahedral tilt twinning alone cannot explain the stripes seen in the HRTEM images, rather a compositional modulation involving the A -site cations is necessary to explain the experimental images. [source]