Search results for "IPR"

showing 10 items of 1515 documents

Structure solution with automated electron diffraction tomography data: different instrumental approaches

2011

Summary Over the past few years automated electron diffraction tomography has become an established technique for structure solution of nano-crystalline material. The intentional choice of an arbitrary tilt axis and thus, the use of nonoriented diffraction patterns (off-zone acquisition) together with fine equidistant sampling of the reciprocal space result in high quality intensity data sets. Coupling automated electron diffraction tomography with electron beam precession (Vincent & Midgley, 1994) enables sampling of intensities between the static slices of reciprocal space and therefore enhances the quality of intensity data further; relatively complex structures have been solved using 3D…

DiffractionHistologybusiness.industryChemistryPathology and Forensic MedicineReciprocal latticeOpticsElectron diffractionElectron tomographySampling (signal processing)Cathode rayEquidistantTomographybusinessJournal of Microscopy

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128-Channel Silicon Strip Detector Installed at a Powder Diffractometer

2004

Silicon strip detectors represent a new class of one-dimensional position-sensitive single photon counting devices. They allow a reduction of measurement time at the powder diffractometers by a factor up to 100 compared to instruments with a single counter, while maintaining comparable count statistics. Present work describes a 128-channel detector working with a standard diffractometer. The detector is 12.8 mm long and covers the angular range of 3.2 deg. We discuss the diffraction geometry in real and reciprocal space, the FWHM of diffraction peaks, and the background level. Measurements were made on standard samples and on complex samples of industrial importance (e. g., portland clinker…

DiffractionMaterials scienceSiliconbusiness.industryMechanical EngineeringDetectorchemistry.chemical_elementCondensed Matter PhysicsPhoton countingReciprocal latticeOpticschemistryMechanics of MaterialsPowder DiffractometerGeneral Materials SciencebusinessPowder diffractionDiffractometerMaterials Science Forum

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Towards automated diffraction tomography. Part II--Cell parameter determination.

2008

Automated diffraction tomography (ADT) allows the collection of three-dimensional (3d) diffraction data sets from crystals down to a size of only few nanometres. Imaging is done in STEM mode, and diffraction data are collected with quasi-parallel beam nanoelectron diffraction (NED). Here, we present a set of developed processing steps necessary for automatic unit-cell parameter determination from the collected 3d diffraction data. Cell parameter determination is done via extraction of peak positions from a recorded data set (called the data reduction path) followed by subsequent cluster analysis of difference vectors. The procedure of lattice parameter determination is presented in detail f…

DiffractionMaterials sciencebusiness.industryAtomic and Molecular Physics and OpticsElectronic Optical and Magnetic MaterialsDiffraction tomographyData setReciprocal latticeOpticsElectron diffractionPrecession electron diffractionTomographybusinessInstrumentationData reductionUltramicroscopy

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Automated electron diffraction tomography - a new tool for nano crystal structure analysis

2011

Automated electron Diffraction Tomography (ADT) comprises an upcoming method for “ab intio” structure analysis of nano crystals. ADT allows fine sampling of the reciprocal space by sequential collection of electron diffraction patterns while tilting a nano crystal in fixed tilt steps around an arbitrary axis. Electron diffraction is collected in nano diffraction mode (NED) with a semi-parallel beam with a diameter down to 50 nm. For crystal tracking micro-probe STEM imaging is used. Full automation of the acquisition procedure allowed optimisation of the electron dose distribution and therefore analysis of highly beam sensitive samples. Cell parameters, space group and reflection intensitie…

DiffractionReflection high-energy electron diffractionChemistrybusiness.industryGeneral ChemistryCondensed Matter Physicsstructure determinationCrystalReciprocal latticeOpticsreciprocal space tomographyElectron diffractionelectron diffraction; reciprocal space tomography; structure determinationelectron diffractionGeneral Materials ScienceDiffraction topographybusinessPowder diffractionElectron backscatter diffraction

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Structural analysis of CdO layers grown on r-plane sapphire (011¯2) by metalorganic vapor-phase epitaxy

2004

Abstract High-quality fully relaxed CdO layers have been grown directly on r -plane sapphire by metalorganic vapor-phase epitaxy. The crystalline structure has been analyzed by high-resolution X-ray diffraction. The structural quality of the (0 0 1) oriented layers degrades as the growth temperature decreases, process which is accompanied by the appearance of pyramidal grains as revealed by scanning force microscopy. The lattice parameters, perpendicular and parallel to the sample surface, have been determined by means of reciprocal space maps taken on asymmetrical reflections and measurements of symmetrical reflections at different azimuths. The epitaxial relationships between the CdO laye…