7,782 research outputs found
Superconducting magnesium diboride films on Silicon with Tc0 about 24K grown via vacuum annealing from stoichiometric precursors
Superconducting magnesium diboride films with Tc0 ~ 24 K and sharp transition
\~ 1 K were successfully prepared on silicon substrates by pulsed laser
deposition from a stoichiometric MgB2 target. Contrary to previous reports,
anneals at 630 degree and a background of 2x10^(-4) torr Ar/4%H2 were performed
without the requirement of Mg vapor or an Mg cap layer. This integration of
superconducting MgB2 films on silicon may thus prove enabling in
superconductor-semiconductor device applications. Images of surface morphology
and cross-section profiles by scanning electron microscopy (SEM) show that the
films have a uniform surface morphology and thickness. Energy dispersive
spectroscopy (EDS) reveals these films were contaminated with oxygen,
originating either from the growth environment or from sample exposure to air.
The oxygen contamination may account for the low Tc for those in-situ annealed
films, while the use of Si as the substrate does not result in a decrease in Tc
as compared to other substrates.Comment: 5 pages, 4 figures, 15 references; due to file size limit, images
were blure
Effective Vortex Pinning in MgB2 thin films
We discuss pinning properties of MgB2 thin films grown by pulsed-laser
deposition (PLD) and by electron-beam (EB) evaporation. Two mechanisms are
identified that contribute most effectively to the pinning of vortices in
randomly oriented films. The EB process produces low defected crystallites with
small grain size providing enhanced pinning at grain boundaries without
degradation of Tc. The PLD process produces films with structural disorder on a
scale less that the coherence length that further improves pinning, but also
depresses Tc
'Cabernet Gernischt' is most likely to be 'Carmenère'
Using a set of 32 microsatellite markers, 'Cabernet Gernischt' has been proven to most likely be 'Carmenère', an old grape cultivar from France, and the progeny of 'Cabernet Franc' and 'Gros Cabernet' has been confirmed. In addition, six 'Cabernet Gernischt' clones with different agronomic traits were identified.
Superconducting gap structure and pinning in disordered MgB2 films
We have performed a comparative study of two thin films of magnesium diboride
(MgB2) grown by different techniques. The critical current density at different
temperatures and magnetic fields was evaluated from magnetisation curves, the
structure of superconducting order parameter was obtained from point-contact
spectroscopy, and the scattering rates were evaluated by fitting the
temperature dependent normal-state resistivity to the two-band model. The films
have similar critical temperatures close to 39 K, but the upper critical fields
were different by a factor of 2 (5.2T and 2.5 T at 20 K). We have found that
the film with higher Hc2 also had stronger scattering in the sigma band and
smaller value of the superconducting gap in this band. As the scattering in
sigma band is primarily due to the defects in boron plane, our results are
consistent with the assumption that disordering the boron planes leads to
enhanced Hc2 and better pinning properties in magnetic field.Comment: Paper presented at EUCAS'0
Susceptibility of Chinese grapes to grape phylloxera
Research Note
An improved continuous compositional-spread technique based on pulsed-laser deposition and applicable to large substrate areas
A new method for continuous compositional-spread (CCS) thin-film fabrication
based on pulsed-laser deposition (PLD) is introduced. This approach is based on
a translation of the substrate heater and the synchronized firing of the
excimer laser, with the deposition occurring through a slit-shaped aperture.
Alloying is achieved during film growth (possible at elevated temperature) by
the repeated sequential deposition of sub-monolayer amounts. Our approach
overcomes serious shortcomings in previous in-situ implementations of CCS based
on sputtering or PLD, in particular the variations of thickness across the
compositional spread and the differing deposition energetics as function of
position. While moving-shutter techniques are appropriate for PLD-approaches
yielding complete spreads on small substrates (i.e. small as compared to
distances over which the deposition parameters in PLD vary, typically about 1
cm), our method can be used to fabricate samples that are large enough for
individual compositions to be analyzed by conventional techniques, including
temperature-dependent measurements of resistivity and dielectric and magnetic
and properties (i.e. SQUID magnetometry). Initial results are shown for spreads
of (Sr,Ca)RuO.Comment: 6 pages, 8 figures, accepted for publication in Rev. Sci. Instru
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