407 research outputs found
Enhancement of Tc by Sr substitution for Ba in Hg-2212 superconductor
The Ba substitution by Sr has been studied in two Hg-2212 series:
Hg2(Ba(1-y)Sr(y))2YCu2O8-d and Hg2(Ba(1-y)Sr(y))2(Y0.80Ca0.20)Cu2O8-d. In both
series a Tc enhancement of about 40 K is observed when Sr substitutes Ba from y
= 0 to y = 1.0.
The y = 0 compound of the first series is the non superconducting
Hg2Ba2YCu2O8-d prototype. In the second series, this y = 0 compound is already
superconducting at 21 K. Indeed the members of this series present a higher
charge carrier density in their CuO2 superconducting planes than their
homologues of the first series due to the doping introduced by the substitution
of 20% of Y by Ca. The compounds of both series were synthesized in high
pressure (3.5 GPa) - high temperature (950 - 1050C) conditions. In both cases
Sr substitution was successful up to the full replacement of Ba (y = 1.0). The
Hg-2212 phases were characterized by XRD, SEM, EDX and a.c. susceptibility.Comment: 14 pages, 7 figures, accepted for publication in Physica
Effect of Sr substitution on superconductivity in Hg2(Ba1-ySry)2YCu2O8-d (part2): bond valence sum approach of the hole distribution
The effects of Sr substitution on superconductivity, and more particulary the
changes induced in the hole doping mechanism, were investigated in
Hg2(Ba1-ySry)2YCu2O8-d by a "bond valence sum" analysis with Sr content from y
= 0.0 to y = 1.0. A comparison with CuBa2YCu2O7-d and Cu2Ba2YCu2O8 systems
suggests a possible explanation of the Tc enhancement from 0 K for y = 0.0 to
42 K for y = 1.0. The charge distribution among atoms of the unit cell was
determined from the refined structure, for y = 0.0 to 1.0. It shows a charge
transfer to the superconducting CuO2 plane via two doping channels pi(1) and
pi(2), i.e. through O2(apical)-Cu and Ba/Sr-O1 bonds respectively.Comment: 13 pages, 5 figures, accepted for publication in Journal of Physics:
Condensed Matte
Recrystallization of silicon by pulsed lasers
Calculation of the evolution of temperature during pulsed laser annealing has been performed. The results are presented in directly useful figures for the two kinds of laser generally used (YAG, Ruby). The results are compared to various experimental measurements performed by RBS. If the crystallographic quality is quite good, TSC and DLTS measurements have shown that electrically active defects are still present after laser annealing
DEPTH MEASUREMENT OF THE PHASE CHANGE UNDER PULSED RUBY LASER ANNEALING
Irradiation of crystalline silicon by pulsed ruby laser induces a surface phase change. A direct measurement of the maximum thickness phase change is reported. Successful comparison with a thermal model is done
Direct observation of the influence of the As-Fe-As angle on the Tc of superconducting SmFeAsOF
The electrical resistivity, crystalline structure and electronic properties
calculated from the experimentally measured atomic positions of the compound
SmFeAsOF have been studied up to pressures ~20GPa. The
correlation between the pressure dependence of the superconducting transition
temperature (Tc) and crystallographic parameters on the same sample shows
clearly that a regular FeAs tetrahedron maximizes Tc, through
optimization of carrier transfer to the FeAs planes as indicated by the
evolution of the electronic band structures.Comment: 15pages, 4 figure
INTERACTION BETWEEN ARGON AND DOPANTS IN SPUTTERED a-Si : H
The concentrations of As, B, H, Ar and Si in sputtered a-Si : H are measured by helium Rutherford backscattering and nuclear reactions analysis. Excess or deficit of hydrogen and argon by comparison with intrinsic a-Si : H are found in presence of dopants at high deposition rate. This is related to the plasma deposition method and would suggest micro grain structure in the deposited layer
- …