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(22) Production(s) de l'année 2017
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CVD Growth of Graphene on SiC (0001): Influence of Substrate Offcut
Auteur(s): Dagher Roy, Jouault B., Paillet M., Bayle M., Nguyen Luan, Portail Marc, Zielinski Marcin, Chassagne Thierry, Cordier Yvon, Michon Adrien
(Article) Publié:
Materials Science Forum, vol. 897 p.731 - 734 (2017)
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What happens in Josephson junctions at high critical current densities
Auteur(s): Massarotti D., Stornaiuolo D., Lucignano P., Caruso R., Galletti L., Montemurro D., Jouault B., Campagnano G., Arani F., Longobardi L., Parlato L., Pepe G., Rotoli G., Tagliacozzo A., Lombardi F., Tafuri F.
(Article) Publié:
Low Temperature Physics, vol. 43 p.816 - 823 (2017)
Texte intégral en Openaccess :
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Hysteretic Critical State in Coplanar Josephson Junction with Monolayer Graphene Barrier
Auteur(s): Massarotti D., Jouault B., Rouco V., Campagnano G., Giuliano D., Lucignano P., Stornaiuolo D., Pepe G. P., Lombardi F., Tafuri F., Tagliacozzo A.
(Article) Publié:
Journal Of Superconductivity And Novel Magnetism, vol. 30 p.5-14 (2017)
Ref HAL: hal-01588920_v1
DOI: 10.1007/s10948-016-3871-x
WoS: WOS:000392300600002
Exporter : BibTex | endNote
1 Citation
Résumé: Coplanar Al/graphene/Al junctions fabricated on the same graphene sheet deposited on silicon carbide (SiC), show robust Josephson coupling at subKelvin temperature, when the separations between the electrodes is below 400 nm. Remarkably, a hysteretic Critical State sets in when ramping an orthogonal magnetic field, with a sudden collapse of the Josephson critical current Ic when turning the field on, and a revival of Ic when inverting the sweep. Similar hysteresis can be found in granular superconducting films which may undergo the Berezinskii-Kosterlitz-Thouless transition. Here, we give quantitative arguments to prove that this odd behavior of the magnetoconductance gives evidence for an incipient Berezinskii-Kosterlitz-Thouless transition with drift and pinning of fluctuating free vortices induced by the current bias.
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Magnetic field driven ambipolar quantum Hall effect in epitaxial graphene close to the charge neutrality point
Auteur(s): Nachawaty A., Yang M., Desrat W., Nanot S., Jabakhanji B., Kazazis D., Yakimova R., Cresti A., Escoffier Walter, Jouault B.
(Article) Publié:
Physical Review B, vol. 96 p.075442 (2017)
Texte intégral en Openaccess :
Ref HAL: hal-01584484_v1
DOI: 10.1103/PhysRevB.96.075442
WoS: 000408620800003
Exporter : BibTex | endNote
2 Citations
Résumé: We have investigated the disorder of epitaxial graphene close to the charge neutrality point (CNP) by various methods: (i) at room temperature, by analyzing the dependence of the resistivity on the Hall coefficient; (ii) by fitting the temperature dependence of the Hall coefficient down to liquid helium temperature; (iii) by fitting themagnetoresistances at low temperature. All methods converge to give a disorder amplitude of (20±10) meV. Because of this relatively low disorder, close to the CNP, at low temperature, the sample resistivity does not exhibit the standard value~h/4e^2 but diverges. Moreover, themagnetoresistance curves have a unique ambipolar behavior,which has been systematically observed for all studied samples.This is a signature of both asymmetry in the density of states and in-plane charge transfer. The microscopic origin of this behavior cannot be unambiguously determined. However, we propose a model in which the SiC substrate steps qualitatively explain the ambipolar behavior.
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Transition from spin-orbit to hyperfine interaction dominated spin relaxation in a cold fluid of dipolar excitons
Auteur(s): Finkelstein Ran, Cohen Kobi, Jouault B., West Ken, Pfeiffer Loren N., Vladimirova M., Rapaport Ronen
(Article) Publié:
Physical Review B, vol. 96 p.085404 (2017)
Texte intégral en Openaccess :
Ref HAL: hal-01577957_v2
DOI: 10.1103/PhysRevB.96.085404
WoS: WOS:000406752500006
Exporter : BibTex | endNote
3 Citations
Résumé: We measure the spin-resolved transport of dipolar excitons in a biased GaAs double quantum well structure. From these measurements we extract both spin lifetime and mobility of the excitons. We find that below a temperature of 4.8K there is a sharp increase in the spin lifetime of the excitons, together with a sharp reduction in their mobility. Below a critical power the spin lifetime increases with increasing mobility and density, while above the critical power the opposite trend is observed. We interpret this transition as evidence of the interplay between two different spin dephasing mechanisms: at low mobility the dephasing is dominated by the hyperfine interaction with the lattice nuclei spins, while at higher mobility the spin-orbit interaction dominates and a Dyakonov-Perel spin relaxation takes over. The excitation power and temperature regime where the hyperfine interaction induced spin dephasing is observed correlates with the regime where a dark dipolar quantum liquid was reported recently on a similar sample.
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High temperature annealing and CVD growth of few-layer graphene on bulk AlN and AlN templates
Auteur(s): Dagher R., Matta S., Parret R., Paillet M., Jouault B., Nguyen L., Portail M., Zielinski M., Chassagne T., Tanaka S., Brault J., Cordier Y., Michon A.
(Article) Publié:
Physica Status Solidi A, vol. 214 p.1600436 (2017)
Ref HAL: hal-01563258_v1
DOI: 10.1002/pssa.201600436
WoS: WOS:000402158300006
Exporter : BibTex | endNote
6 Citations
Résumé: Graphene and AlN are promising materials, interesting to combine together. In this study, we will present first results for direct growth of graphene on bulk AlN and on AlN templates using chemical vapor deposition, including the annealing of these substrates at high temperatures. Atomic force microscopy (AFM) enabled us to study the evolution of the AlN surface morphology after annealing and growth. Few-layer graphene deposition is demonstrated on the basis of X-ray photoemission and Raman spectroscopy
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Electrical transport properties of p-type 4H-SiC
Auteur(s): Contreras S., Konczewicz L., Arvinte Roxana, Peyre H., Chassagne Thierry, Zielinski Marcin, Juillaguet S.
Conférence invité: E-MRS : Wide bandgap materials for electron devices (Lille, FR, 2016-05-02)
Ref HAL: hal-01540938_v1
DOI: 10.1002/pssa.201600679
WoS: WOS:000402158300004
Exporter : BibTex | endNote
9 Citations
Résumé: The Hall hole density pH and Hall mobility µH in highly aluminum-doped 4H-SiC have been investi-gated in the wide temperature range between 100 K and 900 K. After an overview of the literature data related to the analysis of electrical transport experiments, a model taking into account the two upper-most valence bands of heavy and lights holes, one single acceptor energy EA and the empirical Hall factor rHexp has been discussed in details. The limits of the applied model as a function of temperature and acceptor concentration have been considered. For each analyzed sample, the acceptor density NA and the compensation ratio ND/NA have been experimentally assessed by capacitance-voltage and secondary ion mass spectroscopy measurements. Finally, the Hall carrier concentration vs doping level NA-ND as well as ionization energy of acceptor EA vs acceptor concentration NA in 4H-SiC have been discussed.
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