1,319 research outputs found
Heterojunction Hybrid Devices from Vapor Phase Grown MoS
We investigate a vertically-stacked hybrid photodiode consisting of a thin
n-type molybdenum disulfide (MoS) layer transferred onto p-type silicon.
The fabrication is scalable as the MoS is grown by a controlled and
tunable vapor phase sulfurization process. The obtained large-scale p-n
heterojunction diodes exhibit notable photoconductivity which can be tuned by
modifying the thickness of the MoS layer. The diodes have a broad
spectral response due to direct and indirect band transitions of the nanoscale
MoS. Further, we observe a blue-shift of the spectral response into the
visible range. The results are a significant step towards scalable fabrication
of vertical devices from two-dimensional materials and constitute a new
paradigm for materials engineering.Comment: 23 pages with 4 figures. This article has been published in
Scientific Reports. (26 June 2014, doi:10.1038/srep05458
Structure of a model TiO2 photocatalytic interface
The interaction of water with TiO2 is crucial to many of its practical
applications, including photocatalytic water splitting. Following the first
demonstration of this phenomenon 40 years ago there have been numerous studies
of the rutile single-crystal TiO2(110) interface with water. This has provided
an atomic-level understanding of the water-TiO2 interaction. However, nearly
all of the previous studies of water/TiO2 interfaces involve water in the
vapour phase. Here, we explore the interfacial structure between liquid water
and a rutile TiO2(110) surface pre-characterized at the atomic level. Scanning
tunnelling microscopy and surface X-ray diffraction are used to determine the
structure, which is comprised of an ordered array of hydroxyl molecules with
molecular water in the second layer. Static and dynamic density functional
theory calculations suggest that a possible mechanism for formation of the
hydroxyl overlayer involves the mixed adsorption of O2 and H2O on a partially
defected surface. The quantitative structural properties derived here provide a
basis with which to explore the atomistic properties and hence mechanisms
involved in TiO2 photocatalysis
Design and Calibration of a Lightweight Physics-Based Model for Fluid-Mediated Self-Assembly of Robotic Modules
In this paper, we consider a system consisting of multiple floating robotic modules performing self-assembly. Faithfully modeling such a system and its inter-module interactions typically involves capturing the hydrodynamic forces acting on the modules using computationally expensive fluid dynamic modeling tools. This poses restrictions on the usability of the resulting models. Here, we present a new approach towards modeling such systems. First, we show how the hardware and firmware of the robotic modules can be faithfully modeled in a high-fidelity robotic simulator. Second, we develop a physics plugin to recreate the hydrodynamic forces acting on the modules and propose a trajectory-based method for calibrating the plugin model parameters. Our calibration method employs a Particle Swarm Optimization (PSO) algorithm, and consists of minimizing the difference between Mean Squared Displacement (MSD) data extracted from real and simulated trajectories of multiple robotic modules
Measurement of the decay width of He
We have precisely measured decay width of \5LHe and
demonstrated significantly larger - overlap than expected
from the central repulsion - potential, which is derived from
YNG \Lambda$-nucleon interaction.Comment: 4 pages, 3 figure
Proton asymmetry in non-mesonic weak decay of light hypernuclei
We have obtained the decay asymmetry parameters in non-mesonic weak decay of
polarized Lambda-hypernuclei by measuring the proton asymmetry. The polarized
Lambda-hypernuclei, 5_Lambda-He, 12_Lambda-C, and 11_Lambda-B, were produced in
high statistics via the (pi^+,k^+) reaction at 1.05 GeV/c in the forward
angles. Preliminary analysis shows that the decay asymmetry parameters are very
small for these s-shell and p-shell hypernuclei.Comment: 4pages, 4figures, International Conference on Hypernuclear and
Strange Particle Physics (HYP2003
pi^0 decay branching ratios of 5_Lambda-He and 12_Lambda-C hypernuclei
We precisely measured pi^0 branching ratios of 5_Lambda-He and 12_Lambda-C
hypernuclei produced via (pi^+,k^+) reaction. Using these pi^0 branching ratios
with the pi^- branching ratios and the lifetimes, we obtained the pi^0 decay
widths and the non-mesonic weak decay widths at high statistics with the
accuracy of ~5 % (stat) for both hypernuclei.Comment: 4pages, 4figures, International Conference on Hypernuclear and
Strange Particle Physics (HYP2003
Exclusive Measurement of the Nonmesonic Weak Decay of ^{5}_{\Lambda}He Hypernucleus
We performed a coincidence measurement of two nucleons emitted from the
nonmesonic weak decay (NMWD) of ^{5}_{\Lambda}He formed via the
^{6}Li(\pi^+,K^+) reaction. The energies of two nucleons and the pair number
distributions in the opening angle between them were measured. In both np and
nn pairs, we observed a clean back-to-back correlation coming from the two-body
decay of \Lambda p --> n p and \Lambda n --> n n, respectively. The ratio of
the nucleon pair numbers was N_{nn}/N_{np}=0.45 \pm 0.11(stat)\pm 0.03(syst) in
the kinematic region of cos(theta_{NN}) < -0.8. Since each decay mode was
exclusively detected, the measured ratio should be close to the ratio of
\Gamma(\Lambda p --> np)/\Gamma(\Lambda n --> nn).
The ratio is consistent with recent theoretical calculations based on the
heavy meson/direct quark exchange picture.Comment: Submitted to Phys. Rev. lett., 4 pages, 3 figure
Nucleon-nucleon coincidence measurement in the non-mesonic weak decay of 5_Lambda-He and 12_Lambda-C hypernuclei
We have measured both yields of neutron-proton and neutron-neutron pairs
emitted from the non-mesonic weak decay process of 5_Lambda-He and 12_Lambda-C
hypernuclei produced via the (pi^+,K^+) reaction for the first time. We
observed clean back-to-back correlation of the np- and nn-pairs in the
coincidence spectra for both hypernuclei. The ratio of those back-to-back pair
yields, Nnn / Nnp, must be close to the ratio of neutron- and proton-induced
decay widths of the decay, Gn(Lambda n -> nn)/Gp(Lambda p -> np). The obtained
ratios for each hypernuclei support recent calculations based on short-range
interactions.Comment: 4 pages, 1 figure, International Nuclear Physics Conference (INPC
2004), Goteborg, Sweden, June 27 - July 2, 2004, to appear in Nuclear Physics
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