10,195 research outputs found
Anisotropic exciton Stark shift in black phosphorus
We calculate the excitonic spectrum of few-layer black phosphorus by direct
diagonalization of the effective mass Hamiltonian in the presence of an applied
in-plane electric field. The strong attractive interaction between electrons
and holes in this system allows one to investigate the Stark effect up to very
high ionizing fields, including also the excited states. Our results show that
the band anisotropy in black phosphorus becomes evident in the direction
dependent field induced polarizability of the exciton
Ab initio study of neutral (TiO2)n clusters and their interactions with water and transition metal atoms
Cataloged from PDF version of article.We have systematically investigated the growth behavior and stability of small stoichiometric (TiO2)n
(n = 1–10) clusters as well as their structural, electronic and magnetic properties by using the
first-principles plane wave pseudopotential method within density functional theory. In order to find out
the ground state geometries, a large number of initial cluster structures for each n has been searched via
total energy calculations. Generally, the ground state structures for the case of n = 1–9 clusters have at
least one monovalent O atom, which only binds to a single Ti atom. However, the most stable structure of
the n = 10 cluster does not have any monovalent O atom. On the other hand, Ti atoms are at least
fourfold coordinated for the ground state structures for n ≥ 4 clusters. Our calculations have revealed
that clusters prefer to form three-dimensional structures. Furthermore, all these stoichiometric clusters
have nonmagnetic ground state. The formation energy and the highest occupied molecular orbital
(HOMO)–lowest unoccupied molecular orbital (LUMO) gap for the most stable structure of (TiO2)n
clusters for each n have also been calculated. The formation energy and hence the stability increases as
the cluster size grows. In addition, the interactions between the ground state structure of the (TiO2)n
cluster and a single water molecule have been studied. The binding energy (Eb) of the H2O molecule
exhibits an oscillatory behavior with the size of the clusters. A single water molecule preferably binds to
the cluster Ti atom through its oxygen atom, resulting an average binding energy of 1.1 eV. We have also
reported the interaction of the selected clusters (n = 3, 4, 10) with multiple water molecules. We have
found that additional water molecules lead to a decrease in the binding energy of these molecules to the
(TiO2)n clusters. Finally, the adsorption of transition metal (TM) atoms (V, Co and Pt) on the n = 10
cluster has been investigated for possible functionalization. All these elements interact strongly with this
cluster, and a permanent magnetic moment is induced upon adsorption of Co and V atoms. We have
observed gap localized TM states leading to significant HOMO–LUMO gap narrowing, which is
essential to achieve visible light response for the efficient use of TiO2 based materials. In this way,
electronic and optical as well as magnetic properties of TiO2 materials can be modulated by using the
appropriate adsorbate atom
Adsorption of Pt and Bimetallic Pt-Au clusters on the Partially Reduced Rutile (110) TiO2 Surface: A First-Principles Study
Cataloged from PDF version of article.An extensive study of the adsorption of small Ptn (n = 1−8) and bimetallic Pt2Aum (m = 1−5) clusters on the partially reduced rutile (110) TiO2 surface has been nperformed via total energy pseudopotential calculations based on density functional theory. Structures, energetics, and electronic properties of adsorbed Ptn and Pt2Aum clusters have been determined. The surface oxygen vacancy site has been found to be the nucleation center for the growth of Pt clusters. These small Pt clusters strongly interact with the partially reduced surface and prefer to form planar structures for n = 1−6 since the cluster−substrate interaction governs the cluster growth at low Pt coverage. We found a planar-to-threedimensional structural transition at n = 7 for the formation of Ptn clusters on the reduced TiO2 surface. GGA+U calculations have also been performed to get a reasonable description of the reduced oxide surface. We observed significant band gap narrowing upon surface−Ptn cluster interaction which leads to the formation of gap localized Pt states. In the case of bimetallic Pt−Au clusters, Aum clusters have been grown on the Pt2−TiO2 surface. The previously adsorbed Pt dimer at the vacancy site of the reduced surface acts as a clustering center for Au atoms. The presence of the Pt dimer remarkably enhances the binding energy and limits the migration of Au atoms on the titania surface. The charge state of both individual atoms and clusters has been obtained from the Bader charge analysis, and it has been found that charge transfer among the Pt atoms of Ptn clusters and the metal oxide surface is stronger compared to that of Au clusters and the Pt2−TiO2 system
Effect of impurities on the mechanical and electronic properties of Au, Ag, and Cu monatomic chain nanowires
Cataloged from PDF version of article.Ordered arrays of subwavelength hydrogen silsesquioxane (HSQ) nanorods on glass substrates are fabricated using room temperature nanoimprint lithography and anodized aluminum oxide membranes. Moth-eye type nanorod arrays exhibited superior omnidirectional antireflection characteristics in visible wavelengths. The ellipsometric measurements revealed that average specular reflection is remaining below 1% up to 55 degrees incidence angles. Transmission measurements at normal incidence resulted in significant increase in transmitted light intensity with respect to plain glass. Simulations showed that up to 99% transmission could be obtained from double sided tapered HSQ nanorod arrays on HSQ thin film and glass substrates. Achieving large-area, broadband and omnidirectional antireflective surfaces on glass pave the way for applications including photovoltaics. (C) 2011 American Institute of Physics
Non-Simplified SUSY: Stau-Coannihilation at LHC and ILC
If new phenomena beyond the Standard Model will be discovered at the LHC, the
properties of the new particles could be determined with data from the
High-Luminosity LHC and from a future linear collider like the ILC. We discuss
the possible interplay between measurements at the two accelerators in a
concrete example, namely a full SUSY model which features a small stau_1-LSP
mass difference. Various channels have been studied using the Snowmass 2013
combined LHC detector implementation in the Delphes simulation package, as well
as simulations of the ILD detector concept from the Technical Design Report. We
investigate both the LHC and ILC capabilities for discovery, separation and
identification of various parts of the spectrum. While some parts would be
discovered at the LHC, there is substantial room for further discoveries at the
ILC. We finally highlight examples where the precise knowledge about the lower
part of the mass spectrum which could be acquired at the ILC would enable a
more in-depth analysis of the LHC data with respect to the heavier states.Comment: 42 pages, 18 figures, 12 table
Low dark current and high speed ZnO metal–semiconductor–metal photodetector on SiO2/Si substrate
Cataloged from PDF version of article.ZnO thin films are deposited by radio-frequency magnetron sputtering on thermally grown SiO2 on Si substrates. Pt/Au contacts are fabricated by standard photolithography and lift-off in order to form a metal-semiconductor-metal (MSM) photodetector. The dark current of the photodetector is measured as 1 pA at 100V bias, corresponding to 100 pA/cm(2) current density. Spectral photoresponse measurement showed the usual spectral behavior and 0.35 A/W responsivity at a 100V bias. The rise and fall times for the photocurrent are measured as 22 ps and 8 ns, respectively, which are the lowest values to date. Scanning electron microscope image shows high aspect ratio and dense grains indicating high surface area. Low dark current density and high speed response are attributed to high number of recombination centers due to film morphology, deducing from photoluminescence measurements. These results show that as deposited ZnO thin film MSM photodetectors can be used for the applications needed for low light level detection and fast operation. (C) 2014 AIP Publishing LLC
Anomalous single production of the fourth SM family quarks at Tevatron
Possible single productions of fourth family u_{4} and d_{4} quarks via
anomalous q_{4}qV interactions at Tevatron are studied. Signature of such
processes are discussed and compared with the recent results from Tevatron.Comment: 6 pages, 1 figure, 4 table
Skin Lesion Analyser: An Efficient Seven-Way Multi-Class Skin Cancer Classification Using MobileNet
Skin cancer, a major form of cancer, is a critical public health problem with
123,000 newly diagnosed melanoma cases and between 2 and 3 million non-melanoma
cases worldwide each year. The leading cause of skin cancer is high exposure of
skin cells to UV radiation, which can damage the DNA inside skin cells leading
to uncontrolled growth of skin cells. Skin cancer is primarily diagnosed
visually employing clinical screening, a biopsy, dermoscopic analysis, and
histopathological examination. It has been demonstrated that the dermoscopic
analysis in the hands of inexperienced dermatologists may cause a reduction in
diagnostic accuracy. Early detection and screening of skin cancer have the
potential to reduce mortality and morbidity. Previous studies have shown Deep
Learning ability to perform better than human experts in several visual
recognition tasks. In this paper, we propose an efficient seven-way automated
multi-class skin cancer classification system having performance comparable
with expert dermatologists. We used a pretrained MobileNet model to train over
HAM10000 dataset using transfer learning. The model classifies skin lesion
image with a categorical accuracy of 83.1 percent, top2 accuracy of 91.36
percent and top3 accuracy of 95.34 percent. The weighted average of precision,
recall, and f1-score were found to be 0.89, 0.83, and 0.83 respectively. The
model has been deployed as a web application for public use at
(https://saketchaturvedi.github.io). This fast, expansible method holds the
potential for substantial clinical impact, including broadening the scope of
primary care practice and augmenting clinical decision-making for dermatology
specialists.Comment: This is a pre-copyedited version of a contribution published in
Advances in Intelligent Systems and Computing, Hassanien A., Bhatnagar R.,
Darwish A. (eds) published by Chaturvedi S.S., Gupta K., Prasad P.S. The
definitive authentication version is available online via
https://doi.org/10.1007/978-981-15-3383-9_1
Top quark physics in hadron collisions
The top quark is the heaviest elementary particle observed to date. Its large
mass makes the top quark an ideal laboratory to test predictions of
perturbation theory concerning heavy quark production at hadron colliders. The
top quark is also a powerful probe for new phenomena beyond the Standard Model
of particle physics. In addition, the top quark mass is a crucial parameter for
scrutinizing the Standard Model in electroweak precision tests and for
predicting the mass of the yet unobserved Higgs boson. Ten years after the
discovery of the top quark at the Fermilab Tevatron top quark physics has
entered an era where detailed measurements of top quark properties are
undertaken. In this review article an introduction to the phenomenology of top
quark production in hadron collisions is given, the lessons learned in Tevatron
Run I are summarized, and first Run II results are discussed. A brief outlook
to the possibilities of top quark research a the Large Hadron Collider,
currently under construction at CERN, is included.Comment: 84 pages, 32 figures, accepted for publication by Reports on Progress
in Physic
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