83 research outputs found
Omineca Herald, December, 11, 1979
Item does not contain fulltextPaper presented at the ICAS Workshop, November 30-December 1.Würzburg : [S.n.
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Lattice matched Volmer–Weber growth of Fe3Si on GaAs(001) - the influence of the growth rate
We investigate the formation of lattice matched single-crystalline Fe3Si/GaAs(001) ferromagnet/semiconductor hybrid structures by Volmer-Weber island growth, starting from the epitaxial growth of isolated Fe3Si islands up to the formation of continuous films as a result of island coalescence. We find coherent defect-free layers exhibiting compositional disorder near the Fe3Si/GaAs - interface for higher growth rates, whereas they are fully ordered for lower growth rates. © 2019 IOP Publishing Ltd
Macro- and micro-strain in GaN nanowires on Si(111)
We analyze the strain state of GaN nanowire ensembles by x-ray diffraction.
The nanowires are grown by molecular beam epitaxy on a Si(111) substrate in a
self-organized manner. On a macroscopic scale, the nanowires are found to be
free of strain. However, coalescence of the nanowires results in micro-strain
with a magnitude from +-0.015% to +-0.03%.This micro-strain contributes to the
linewidth observed in low-temperature photoluminescence spectra
In situ x-ray diffraction study of epitaxial growth of ordered Fe3Si films
Molecular beam epitaxy of Fe3Si on GaAs(001) is studied in situ by grazing
incidence x-ray diffraction. Layer-by-layer growth of Fe3Si films is observed
at a low growth rate and substrate temperatures near 200 degrees Celsius. A
damping of x-ray intensity oscillations due to a gradual surface roughening
during growth is found. The corresponding sequence of coverages of the
different terrace levels is obtained. The after-deposition surface recovery is
very slow. Annealing at 310 degrees Celsius combined with the deposition of one
monolayer of Fe3Si restores the surface to high perfection and minimal
roughness. Our stoichiometric films possess long-range order and a high quality
heteroepitaxial interface.Comment: 8 pages, 3 figure
Residual disorder and diffusion in thin Heusler alloy films
Co2FeSi/GaAs(110) and Co2FeSi/GaAs(111)B hybrid structures were grown by
molecular-beam epitaxy and characterized by transmission electron microscopy
(TEM) and X-ray diffraction. The films contained inhomogeneous distributions of
ordered L2_1 and B2 phases. The average stoichiometry was controlled by lattice
parameter measurements, however diffusion processes lead to inhomogeneities of
the atomic concentrations and the degradation of the interface, influencing
long-range order. An average long-range order of 30-60% was measured by
grazing-incidence X-ray diffraction, i.e. the as-grown Co2FeSi films were
highly but not fully ordered. Lateral inhomogeneities of the spatial
distribution of long-range order in Co2FeSi were found using dark-field TEM
images taken with superlattice reflections
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Characterization of L21 order in Co2FeSi thin films on GaAs
Co2FeSi/GaAs(110) and Co2FeSi/GaAs(-1-1-1)B hybrid structures were grown by molecular-beam epitaxy (MBE) and characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The films contain inhomogeneous distributions of ordered L21 and B2 phases. The average stoichiometry could be determined by XRD for calibration of the MBE sources. Diffusion processes lead to inhomogeneities, influencing long-range order. An average L21 ordering of up to 65% was measured by grazing-incidence XRD. Lateral inhomogeneities of the spatial distribution of long-range order in Co2FeSi were imaged using dark-field TEM with superlattice reflections and shown to correspond to variations of the Co/Fe ratio
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