5,683 research outputs found
High-throughput synthesis of thermoelectric CaCoO films
Properties of complex oxide thin films can be tuned over a range of values as
a function of mismatch, composition, orientation, and structure. Here, we
report a strategy for growing structured epitaxial thermoelectric thin films
leading to improved Seebeck coefficient. Instead of using single-crystal
sapphire substrates to support epitaxial growth, CaCoO films are
deposited, using the Pulsed Laser Deposition technique, onto AlO
polycrystalline substrates textured by Spark Plasma Sintering. The structural
quality of the 2000 \AA thin film was investigated by Transmission Electron
Microscopy, while the crystallographic orientation of the grains and the
epitaxial relationships were determined by Electron Back Scatter Diffraction.
The use of a polycrystalline ceramic template leads to structured films that
are in good local epitaxial registry. The Seebeck coefficient is about 170
V/K at 300 K, a typical value of misfit material with low carrier density.
This high-throughput process, called combinatorial substrate epitaxy, appears
to facilitate the rational tuning of functional oxide films, opening a route to
the epitaxial synthesis of high quality complex oxides.Comment: Submitted to Applied Physics Letters (2013
Universal Torsion-Induced Interaction from Large Extra Dimensions
We consider the Kaluza-Klein (KK) scenario in which only gravity exists in
the bulk. Without the assumption of symmetric connection, the presence of brane
fermions induces torsion. The result is a universal axial contact interaction
that dominates those induced by KK gravitons. This enhancement arises from a
large spin density on the brane. Using a global fit to Z-pole observables, we
find the 3 sigma bound on the scale of quantum gravity to be 28 TeV for n=2. If
Dirac or light sterile neutrinos are present, the data from SN1987A increase
the bound to \sqrt{n}M_S >= 210 TeV.Comment: 9 pages REVTeX, 1 postscript figure, uses axodraw.st
Raman fingerprints of ultrasmall nanodiamonds produced from adamantane
The synthesis of ultrasmall (2-5 nm) nanodiamonds purely from adamantane at
pressure of 12 GPa is reported. Their structural features have been studied by
Raman spectroscopy. The unusual vibration band containing a number of
pronounced maxima at about 1147, 1245, 1344, and 1456 cm-1 was detected in
Raman spectra. The band is confidently identified with the bending vibrational
modes of CHx groups terminating the nanodiamonds surface. Excessively intense
mode at 1344 cm-1 is explained by its coupling with the 1328 cm-1 diamond
phonons. The Raman band found is proposed to be used for express recognition of
ultrasmall nanodiamonds produced from adamantane and other hydrocarbons with a
high hydrogen content. Moreover, polarized CH bonds on a diamond surface are
sensitive to environmental conditions. This opens up opportunities for using
the diamond produced from adamantane as ultrasmall nanosensors in biology,
chemistry, and medicineComment: 12 pages, 6 figure
Charge localization at the interface between La1-xSrxMnO3 and the infinite layers cuprate CaCuO2
(CaCuO2)m/(La0.7Sr0.3MnO3)n superlattices, consisting of the infinite layers
cuprate CaCuO2 and the optimally doped manganite La1-xSrxMnO3, were grown by
pulsed laser deposition. The transport properties are dominated by the
manganite block. X-Ray Absorption spectroscopy measurements show a clear
evidence of an orbital reconstruction at the interface, ascribed to the
hybridization between the Cu 3d3z2-r2 and the Mn 3d3z2-r2 orbitals via
interface apical oxygen ions. Such a mechanism localizes holes at the
interfaces, thus preventing charge transfer to the CaCuO2 block. Some charge
(holes) transfer occurs toward the La0.7Sr0.3MnO3 block in strongly oxidized
superlattices, contributing to the suppression of the magnetotransport
properties.Comment: 20 pages, 6 figure
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