2,097 research outputs found
Nanostructure phase and interface engineering via controlled Au self-assembly on GaAs(001) surface
We have investigated the temperature-dependent morphology and composition
changes occurring during a controlled self-assembling of thin Au film on the
Gallium arsenide (001) surface utilizing electron microscopy at nano and atomic
levels. It has been found that the deposition of 2 ML of Au at a substrate
temperature lower than 798 K leads to the formation of pure Au nanoislands. For
the deposition at a substrate temperature of about 798 K the nanostructures of
the stoichiometric AuGa phase were/had been grown. Gold deposition at higher
substrate temperatures results in the formation of octagonal nanostructures
composed of an AuGa2 alloy. We have proved that the temperature-controlled
efficiency of Au-induced etching-like of the GaAs substrate follows in a
layer-by-layer manner leading to the enrichment of the substrate surface in
gallium. The excess Ga together with Au forms liquid droplets which, while
cooling the sample to room temperature, crystallize therein developing
crystalline nanostructures of atomically-sharp interfaces with the substrate.
The minimal stable cluster of 3 atoms and the activation energy for the surface
diffusion Ed=0.816+-0.038eV was determined. We show that by changing the
temperature of the self-assembling process one can control the phase, interface
and the size of the nanostructures formed
High-precision measurement of the half-life of Ga
The beta-decay half-life of 62Ga has been studied with high precision using
on-line mass separated samples. The decay of 62Ga which is dominated by a 0+ to
0+ transition to the ground state of 62Zn yields a half-life of T_{1/2} =
116.19(4) ms. This result is more precise than any previous measurement by
about a factor of four or more. The present value is in agreement with older
literature values, but slightly disagrees with a recent measurement. We
determine an error weighted average value of all experimental half-lives of
116.18(4) ms.Comment: 9 pages, 5 figures, accepted for publication in PR
Decay of proton-rich nuclei between 39Ti and 49Ni
Decay studies of very neutron-deficient nuclei ranging from 39Ti to 49Ni have
been performed during a projectile fragmentation experiment at the GANIL/LISE3
separator. For all nuclei studied in this work, 39,40Ti, 42,43Cr, 46Mn,
45,46,47Fe and 49Ni, half-lives and decay spectra have been measured. In a few
cases, gamma coincidence measurements helped to successfully identify the
initial and final states of transitions. In these cases, partial decay scheme
are proposed. For the most exotic isotopes, 39Ti, 42Cr, 45Fe and 49Ni, which
are candidates for two-proton radioactivity from the ground state, no clear
evidence of this process is seen in our spectra and we conclude rather on a
delayed particle decay.Comment: 12 pages, 15 figures, submitted for publication in Eur. Phys. J.
First observation of 55,56Zn
In an experiment at the SISSI/LISE3 facility of GANIL, the most proton-rich
zinc isotopes 55,56Zn have been observed for the first time. The experiment was
performed using a high-intensity 58Ni beam at 74.5 MeV/nucleon impinging on a
nickel target. The identification of 55,56Zn opens the way to 54Zn, a good
candidate for two-proton radioactivity according to theoretical predictions.Comment: 2 pages, 1 figure, accepted for publication in Eur. Phys. J.
Into the Origin of Electrical Conductivity for the Metal-Semiconductor Junction at the Atomic Level
The metal-semiconductor (M-S) junction based devices are commonly used in all
sorts of electronic devices. Their electrical properties are defined by the
metallic phase properties with a respect to the semiconductor used. Here we
make an in-depth survey on the origin of the M-S junction at the atomic scale
by studying the properties of the AuIn2 nanoelectrodes formed on the InP(001)
surface by the in situ electrical measurements in combination with a detailed
investigation of atomically resolved structure supported by the first-principle
calculations of its local electrical properties. We have found that a different
crystallographic orientation of the same metallic phase with a respect to the
semiconductor structure influences strongly the M-S junction rectifying
properties by subtle change of the metal Fermi level and influencing the band
edge moving at the interface. This ultimately changes conductivity regime
between Ohmic and Schottky type. The effect of crystallographic orientation has
to be taken into account in the engineering of the M-S junction-based
electronic devices
The rp-process and new measurements of beta-delayed proton decay of light Ag and Cd isotopes
Recent network calculations suggest that a high temperature rp-process could
explain the abundances of light Mo and Ru isotopes, which have long challenged
models of p-process nuclide production. Important ingredients to network
calculations involving unstable nuclei near and at the proton drip line are
-halflives and decay modes, i.e., whether or not -delayed proton
decay takes place. Of particular importance to these network calculation are
the proton-rich isotopes Ag, Ag, Cd and Cd. We
report on recent measurements of -delayed proton branching ratios for
Ag, Ag, and Cd at the on-line mass separator at GSI.Comment: 4 pages, uses espcrc1.sty. Proceedings of the 4th International
Symposium Nuclei in the Cosmos, June 1996, Notre Dame/IN, USA, Ed. M.
Wiescher, to be published in Nucl.Phys.A. Also available at
ftp://ftp.physics.ohio-state.edu/pub/nucex/nic96-gs
Chitin and carbon nanotube composites as biocompatible scaffolds for neuron growth
Preparation of biocompatible and electrically-conducting chitin nanotube composite scaffold for potential use in implantable electrode for stimulation and repair of neurons.</p
Proton Drip-Line Calculations and the Rp-process
One-proton and two-proton separation energies are calculated for proton-rich
nuclei in the region . The method is based on Skyrme Hartree-Fock
calculations of Coulomb displacement energies of mirror nuclei in combination
with the experimental masses of the neutron-rich nuclei. The implications for
the proton drip line and the astrophysical rp-process are discussed. This is
done within the framework of a detailed analysis of the sensitivity of rp
process calculations in type I X-ray burst models on nuclear masses. We find
that the remaining mass uncertainties, in particular for some nuclei with
, still lead to large uncertainties in calculations of X-ray burst light
curves. Further experimental or theoretical improvements of nuclear mass data
are necessary before observed X-ray burst light curves can be used to obtain
quantitative constraints on ignition conditions and neutron star properties. We
identify a list of nuclei for which improved mass data would be most important.Comment: 20 pages, 9 figures, 2 table
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