616 research outputs found
Transport properties of 2D graphene containing structural defects
We propose an extensive report on the simulation of electronic transport in
2D graphene in presence of structural defects. Amongst the large variety of
such defects in sp carbon-based materials, we focus on the Stone-Wales
defect and on two divacancy-type reconstructed defects. First, based on ab
initio calculations, a tight-binding model is derived to describe the
electronic structure of these defects. Then, semiclassical transport properties
including the elastic mean free paths, mobilities and conductivities are
computed using an order-N real-space Kubo-Greenwood method. A plateau of
minimum conductivity () is progressively
observed as the density of defects increases. This saturation of the decay of
conductivity to is associated with defect-dependent
resonant energies. Finally, localization phenomena are captured beyond the
semiclassical regime. An Anderson transition is predicted with localization
lengths of the order of tens of nanometers for defect densities around 1%.Comment: 17 pages, 17 figures, submitted to Phys. Rev.
Anisotropic Vapor HF etching of silicon dioxide for Si microstructure release
Damages are created in a sacrificial layer of silicon dioxide by ion
implantation to enhance the etch rate of silicon-dioxide in liquid and vapor
phase hydrofluoric acid. The etch rate ratio between implanted and unimplanted
silicon dioxide is more than 150 in vapor hydrofluoric acid (VHF). This feature
is of interest to greatly reduce the underetch of microelectromechanical
systems anchors. Based on the experimentally extracted etch rate of unimplanted
and implanted silicon dioxide, the patterning of the sacrificial layer can be
predicted by simulation
Tailoring the Crystallographic Texture and Electrical Properties of Inkjet-printed Interconnects for Use in Microelectronics
International audienceIn this paper, silver nanoparticles with a mean diameter of 40 nm are studied for future applications in microelectronic devices. The enhanced diffusivity of nanoparticles is exploited to fabricate electrical interconnects at low temperature. Sintering condition has been tuned to tailor the grain size so that electrical resistivity can be lowered down to 3.4 µOhm∙cm. In this study, a {111}-textured gold thin film has been used to increase diffusion routes. The combined effects of the substrate crystalline orientation and the sintering condition have been demonstrated to have a significant impact on microstructures. In particular, a {111} fiber texture is developed above 300°C in printed silver only if the underlying film exhibits a preferential orientation. This condition appeared as essential for the efficiency of the gold wire-bonding process step. Thus, inkjet-printed interconnects show a prospective potential compared to conventional subtractive technique and offers new opportunities for low cost metallization in electronics packaging
Evidential uncertainties on rich labels for active learning
Recent research in active learning, and more precisely in uncertainty
sampling, has focused on the decomposition of model uncertainty into reducible
and irreducible uncertainties. In this paper, we propose to simplify the
computational phase and remove the dependence on observations, but more
importantly to take into account the uncertainty already present in the labels,
\emph{i.e.} the uncertainty of the oracles. Two strategies are proposed,
sampling by Klir uncertainty, which addresses the exploration-exploitation
problem, and sampling by evidential epistemic uncertainty, which extends the
reducible uncertainty to the evidential framework, both using the theory of
belief functions
Real bird dataset with imprecise and uncertain values
The theory of belief functions allows the fusion of imperfect data from
different sources. Unfortunately, few real, imprecise and uncertain datasets
exist to test approaches using belief functions. We have built real birds
datasets thanks to the collection of numerous human contributions that we make
available to the scientific community. The interest of our datasets is that
they are made of human contributions, thus the information is therefore
naturally uncertain and imprecise. These imperfections are given directly by
the persons. This article presents the data and their collection through
crowdsourcing and how to obtain belief functions from the data
Impact of variable frequency microwave and rapid thermal sintering on microstructure of inkjet-printed silver nanoparticles
International audienceThe effect of thermal profile on microstructure is studied in the frame of thin films deposited by inkjet-printing technology. The role of sintering temperature and thermal ramp is particularly investigated. Fast heating ramps exhibit coarse grains and pores, especially when a hybrid microwave curing is performed. This enhanced growth is attributed to the quick activation of densifying sintering regimes without undergoing thermal energy loss at low temperature. Microstructural evolution of various sintered inkjet-printed films is correlated with electrical resistivity and with the Young's modulus determined by nanoindentation. A strong link between those three parameters is highlighted during experiments giving credit to either a surface or a fully volumetric sintering, according to the process. Sintering is then mainly triggered by surface mass transfer or by grain boundary diffusion respectively. Silver thin-films with an electrical resistivity 4 to 5 times higher than the bulk has been reached in a few minutes and with a Young's modulus of 38 GPa
Hemodynamic responses to intracoronary infusion of calcitonin gene-related peptide in patients with congestive heart failure
First-principles prediction of lattice coherency in van der Waals heterostructures
The emergence of superconductivity in slightly-misaligned graphene bilayer
[1] and moir\'e excitons in MoSe-WSe van der Waals (vdW)
heterostructures [2] is intimately related to the formation of a 2D
superlattice in those systems. At variance, perfect primitive lattice matching
of the constituent layers has also been reported in some vdW-heterostructures
[3-5], highlighting the richness of interfaces in the 2D world. In this work,
the determination of the nature of such interface, from first principles, is
demonstrated. To do so, an extension of the Frenkel-Kontorova (FK) model [6] is
presented, linked to first-principles calculations, and used to predict lattice
coherency for a set of 56 vdW-heterostructures. Computational predictions agree
with experiments, when available. New superlattices as well as
perfectly-matching interfaces are predicted.Comment: 16 pages, 3 figure
Chip integration using inkjet-printed silver conductive tracks reinforced by electroless plating for flexible board packages
International audienceInkjet-printing of interconnects is a maskless technology that has attracted great interest for printed electronics and packaging applications. Gemalto is expecting by motivated and developing skills and knowledge in this area to be at the forefront of European Security innovation and to answer to a continuous market pressure for higher security, lower cost and more secure complex systems. With an increasing need for flexible and mass deliveries of advanced secure personal devices such as: electronic passports, ID cards, driver licenses, other smartcards, e-documents and tokens. EMSE is seeing in these new developments an exciting brand new area of research situated between material science and electronics. In this frame, deposit and pattern creation for chip interconnection require specific behaviors which have to be scientifically understood to pursue industrial harmonious implementation. Both groups collaborated on inkjet-printed electronic routing from deposition to sintering and characterization, using collaborative means provided on Micro-PackS platform
Two-Dimensional Graphene with Structural Defects: Elastic Mean Free Path, Minimum Conductivity, and Anderson Transition
4 páginas, 4 figuras.-- PACS numbers: 73.23. b, 72.15.Rn, 73.43.Qt.-- et al.Quantum transport properties of disordered graphene with structural defects (Stone-Wales and divacancies) are investigated using a realistic π-π* tight-binding model elaborated from ab initio calculations. Mean free paths and semiclassical conductivities are then computed as a function of the nature and density of defects (using an order-N real-space Kubo-Greenwood method). By increasing the defect density, the decay of the semiclassical conductivities is predicted to saturate to a minimum value of 4e2/πh over a large range (plateau) of carrier density (>0.5×1014  cm-2). Additionally, strong contributions of quantum interferences suggest that the Anderson localization regime could be experimentally measurable for a defect density as low as 1%.J.-C. C. and A. L. acknowledge financial support from
the FNRS of Belgium. Parts of this work are connected to
the Belgian Program on Interuniversity Attraction Poles
(PAI6), to the NanoHymo ARC, to the ETSF e-I3 project
(Grant No. 211956), and to the NANOSIM-GRAPHENE
Project No. ANR-09-NANO-016-01.Peer reviewe
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