17,930 research outputs found
Energetics and Electronic Properties of Interstitial Chlorine in CdTe
Indexación: Scopus.We acknowledge support from Chilean funding agency FONDECYT under Grants No. 1170480 (W.O.) and 1171807 (E.M-P.). Powered@NLHPC: This research was partially supported by the supercomputing infrastructure of the NLHPC (ECM-02).The role of interstitial chlorine in the electronic properties of CdTe is addressed by density functional theory calculations including hybrid functionals and large unit cells. The stability and diffusion energy barriers of the impurity are analyzed as a function of the Fermi level position in the band gap. Chlorine is found to be stable in at least five interstitial sites with rather close formation energies, suggesting that they are all probable to be found. In p-type CdTe, the most stable sites are at the center of a CdTe bond and at a split-interstitial configuration, both acting as shallow donors. Whereas in n-type CdTe, it is found at the tetrahedral site surrounded by Cd hosts, acting as a shallow acceptor. We also find that chlorine can induce a deep acceptor level in the bandgap after binding with three Cd host atoms, which can explain the experimentally observed high resistivity in Cl-doped CdTe. The energy barriers for chlorine diffusion in both p-type and n-type CdTe are also discussed. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheimhttps://onlinelibrary.wiley.com/doi/full/10.1002/pssb.20180021
Field ionization electrodes Patent
Electrodes having array of small surfaces for field ionizatio
Racial categories in machine learning
Controversies around race and machine learning have sparked debate among
computer scientists over how to design machine learning systems that guarantee
fairness. These debates rarely engage with how racial identity is embedded in
our social experience, making for sociological and psychological complexity.
This complexity challenges the paradigm of considering fairness to be a formal
property of supervised learning with respect to protected personal attributes.
Racial identity is not simply a personal subjective quality. For people labeled
"Black" it is an ascribed political category that has consequences for social
differentiation embedded in systemic patterns of social inequality achieved
through both social and spatial segregation. In the United States, racial
classification can best be understood as a system of inherently unequal status
categories that places whites as the most privileged category while signifying
the Negro/black category as stigmatized. Social stigma is reinforced through
the unequal distribution of societal rewards and goods along racial lines that
is reinforced by state, corporate, and civic institutions and practices. This
creates a dilemma for society and designers: be blind to racial group
disparities and thereby reify racialized social inequality by no longer
measuring systemic inequality, or be conscious of racial categories in a way
that itself reifies race. We propose a third option. By preceding group
fairness interventions with unsupervised learning to dynamically detect
patterns of segregation, machine learning systems can mitigate the root cause
of social disparities, social segregation and stratification, without further
anchoring status categories of disadvantage
Renormalized coordinate approach to the thermalization process
We consider a particle in the harmonic approximation coupled linearly to an
environment. modeled by an infinite set of harmonic oscillators. The system
(particle--environment) is considered in a cavity at thermal equilibrium. We
employ the recently introduced notion of renormalized coordinates to
investigate the time evolution of the particle occupation number. For
comparison we first present this study in bare coordinates. For a long ellapsed
time, in both approaches, the occupation number of the particle becomes
independent of its initial value. The value of ocupation number of the particle
is the physically expected one at the given temperature. So we have a Markovian
process, describing the particle thermalization with the environment. With
renormalized coordinates no renormalization procedure is required, leading
directly to a finite result.Comment: 16 pages, LATEX, 2 figure
Modelling of epitaxial graphene functionalization
A new model for graphene, epitaxially grown on silicon carbide is proposed.
Density functional theory modelling of epitaxial graphene functionalization by
hydrogen, fluorine and phenyl groups has been performed with hydrogen and
fluorine showing a high probability of cluster formation in high adatom
concentration. It has also been shown that the clusterization of fluorine
adatoms provides midgap states in formation due to significant flat distortion
of graphene. The functionalization of epitaxial graphene using larger species
(methyl and phenyl groups) renders cluster formation impossible, due to the
steric effect and results in uniform coverage with the energy gap opening.Comment: 15 pages, 4 figures, to appear in Nanotechnolog
Soil quality and farm profitability: A win-win situation
Farmers are more likely to adopt and adapt improved soil management strategies if their efforts lead to an immediate economic benefit. An encouraging policy environment, as well as farmer organisation also stimulates the adoption of conservation practices. In Mexico, farmers are adapting their maize-based cropping systems to conservation agriculture, leading to both higher profits and soil conservation
Quantum capacitor with discrete charge-anticharge: spectrum and forces
The quantum capacitor with discrete charge is modeled by a Hamiltonian
containing an inductive intrinsic term (tunnel effect between plates). The
spectrum is obtained using a double Hilbert space. Fluctuations in the
charge-anticharge pairs (zero total charge) give rise to an elementary
attraction which is compared to the Casimir force. In this case, the
field-fluctuations force could be also interpreted as charge-fluctuations
force
The distribution of oxygen at the Ni81Fe19/Ta interface
The knowledge of how oxygen atoms are distributed at a magnetic-metal /
oxide, or magnetic-metal / non-magnetic-metal interface, can be an useful tool
to optimize device production. Multilayered Ni81Fe19 / Ta samples consisting of
15 bilayers of 2.5 nm each, grown onto glass substrates by magnetron sputtering
from Ni81Fe19 and Ta targets, have been investigated. X-ray absorption near
edge structure, extended X-Ray absorption fine structure, small angle X-ray
diffraction, and simulations, were used to characterize the samples. Oxygen
atoms incorporated onto Ni81Fe19 films during O2 exposition are mainly bonded
to Fe atoms. This partial oxidation of the Ni81Fe19 surface works as a barrier
to arriving Ta atoms, preventing intermixing at the Ni81Fe19 / Ta interface.
The reduction of the Ni81Fe19 surface by the formation of TaO x is observed.Comment: 14 pages, 9 figures, accepted for publication in Advances in
Materials Science and Engineerin
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