31 research outputs found
Sedimentology and provenance of Carboniferous and Permian rocks of Athens County, Southeastern Ohio
Originally prepared for the 1998 North-Central Section meeting of the Geological Society of America
Role of pair-breaking and phase fluctuations in c-axis tunneling in underdoped BiSrCaCuO
The Josephson Plasma Resonance is used to study the c-axis supercurrent in
the superconducting state of underdoped
BiSrCaCuO with varying degrees of controlled
point-like disorder, introduced by high-energy electron irradiation. As
disorder is increased, the Josephson Plasma frequency decreases proportionally
to the critical temperature. The temperature dependence of the plasma frequency
does not depend on the irradiation dose, and is in quantitative agreement with
a model for quantum fluctuations of the superconducting phase in the CuO
layers.Comment: 2 pages, submitted to the Proceedings of M2S-HTSC VIII Dresde
Electrical and structural properties of MgB2 films prepared by sequential deposition of B and Mg on the NbN buffered Si(100) substrate
We introduce a simple method of an MgB2 film preparation using sequential
electron-beam evaporation of B-Mg two-layer (followed by in-situ annealing) on
the NbN buffered Si(100) substrate. The Transmission Electron Microscopy
analyses confirm a growth of homogeneous nanogranular MgB2 films without the
presence of crystalline MgO. A sensitive measurement of temperature dependence
of microwave losses shows a presence of intergranular weak links close the
superconducting transition only. The MgB2 films obtained, about 200 nm thick,
exhibit a maximum zero resistance critical temperature of 36 K and critical
current density of 3x10^7 A/cm^2 at 13.2 KComment: 11 pages, 6 figures, submitted to Appl. Phys. Let
Strong Pinning in High Temperature Superconductors
Detailed measurements of the critical current density jc of YBa2Cu3O7 films
grown by pulsed laser deposition reveal the increase of jc as function of the
filmthickness. Both this thickness dependence and the field dependence of the
critical current are consistently described using a generalization of the
theory of strong pinning of Ovchinnikov and Ivlev [Phys. Rev. B 43, 8024
(1991)]. From the model, we deduce values of the defect density (10^21 m^-3)
and the elementary pinning force, which are in good agreement with the
generally accepted values for Y2O3-inclusions. In the absence of clear evidence
that the critical current is determined by linear defects or modulations of the
film thickness, our model provides an alternative explanation for the rather
universal field dependence of the critical current density found in YBa2Cu3O7
films deposited by different methods.Comment: 11 pages; 8 Figures; Published Phys. Rev. B 66, 024523 (2002
Origin and evolution of the Bezedna lake–mire complex in the Lublin area (East Poland): a case study for permafrost lakes in karstic regions
Structural and electrical characterization of self-assembled films of gold nanoparticles linked by thiol molecules
X-ray characterization of films formed by pulsed laser deposition on cold substrates from YBaCuO targets
Grazing-incidence X-ray diffraction supplemented with atomic force microscopy and secondary ion mass spectroscopy were applied to the characterization of films deposited by laser ablation on cold substrates from YBaCuO targets and subsequently irradiated with additional laser pulses of lower energy density. Evolution of X-ray diffraction pattern was observed as a function of irradiation dose. For the as-deposited films the pattern was typical of the amorphized solids. For the films irradiated with doses higher than the threshold, the pattern was enriched with the diffraction peaks, whose general features, like peak positions, widths and relative intensities were almost independent of the dose. The size of the crystallites was deduced from the peak widths to be not smaller than 12-16 nm. Comparison of the pattern with patterns of known phases indicates that, apart of the amorphous component, a structure with an admixture of some new metastable or high temperature phase(s) is formed during the process of pulsed laser annealing. The atomic force microscopy observations revealed that the surface roughness shows a pronounced minimum at low irradiation doses. The secondary ion mass spectroscopy investigation confirms that the strongest chemical changes (increase in concentration of yttrium and copper) due to irradiation with higher doses are observed in the near-surface film material