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High quality single-crystal Au(100) buffers have been grown on GaAs(100) or MgO(100) substrates via a thin bcc Fe(100) nucleation layer. Using RHEED, LEED and Auger spectroscopy the growth of Ni overlayers at room temperature was observed to follow an epitaxial layer-by-layer mode for 2 monolayers, after which islanding occured. Detailed analysis of the Auger signal reveals that atomic mixing appears within the first completed layer. Grazing incidence diffraction has been used to investigate the structure of 5–10 nm films. A mixture of (100) and (110) grains have been characterized; the latter orientation shows a large number of stacking faults along the  direction in agreement with the Au direction.
Crx thin films on Si and fused-SiO2
substrates were prepared using ion-beam sputtering deposition. Films with x
= 0.69 and x = 0.49 were characterised by X-ray diffraction and conversion
electron Mössbauer spectroscopy experiments, and concurrently the
elastic and plastic behaviours were investigated through indentation tests.
For x = 0.69, the paramagnetic bcc structure is observed, while the
indentation modulus and hardness values are found to be 160 and 8.7 GPa,
respectively. For x = 0.49, a strongly
-textured paramagnetic phase
is evidenced, having the A15 structure. Mössbauer measurements also
allowed the site occupancy to be determined. The structural change from bcc
to A15 phase yields a 50% increase in hardness, while the indentation
modulus remains unchanged. This particular behaviour is discussed in terms
of distances between near neighbours and Burgers vector length in both bcc
and A15 structures. The results obtained here provide motivation to pursue
the present study through wear experiments.
Polycrystalline iron thin films on ion-etched monocrystalline In0.5Ga0.5As/InP (001)
substrates were prepared using ion-beam sputtering deposition. The interface reaction was
characterised by X-ray diffraction and conversion electron Mössbauer spectroscopy experiments, after
annealing in vacuum for 1 h at temperatures between 350 and 450 °C. Interdiffusion phenomena mainly
result in the formation of five new phases, namely metallic-In, InAs, Fe2As, Fe2InxAs
$0 \leq x \leq 0.2$
$x = 0.2 - 0.3$
), in agreement with the predictions of the phase diagrams. InAs results
from the decomposition of the semiconductor substrate and remains (001)-textured. The iron-arsenide
grains grow into the substrate below the Fe/In0.5Ga0.5As interface. The In precipitates reach ~40 nm in
size after 1 h annealing at 450 °C, while the Fe3Ga
Asx phase appears at 400–450 °C with an either
textured or disordered structure. Finally, the overall activation energy for the thermal reaction is
calculated to be 1.5 eV in the latter temperature range.
We report on the fabrication and structural characterization of arrays of superconducting nanowires by electroplating lead into the nanopores of track-etched polymer membranes. The diameters of the lead nanowires range from 400 down to 70 nm, whereas their length is about 20 μm. Large enhancement of the critical field has been observed in good agreement with the Ginsburg–Landau–Silin theory. By comparing the predicted critical field enhancement for thin cylinders with experimental results, we have extracted the effective penetration depth. The dependence of the effective penetration depth and electron mean free path on the wire diameter is also discussed.
The behaviour of pyrite in the process of mechanical milling in air has been
examined. Milled powders were characterized by scanning electron microscopy, Mössbauer
spectroscopy working in transmission geometry and X-ray diffraction. In the presence of
oxygen, pyrite can readily be transformed to ferrous sulphate monohydrate, which
indicates that the Fe(II) goes from a low-spin state to to a high-spin state. The
transformation mechanism is saturated after about 60 hours milling, but however it can
be markedly prolonged by further ageing at room temperature. The results also indicate
that mechanical milling is a useful room temperature process of material production.
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