| 1. |
- Ferrari, A. C., et al.
(författare)
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Science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems
- 2015
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 7:11, s. 4598-4810
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Tidskriftsartikel (refereegranskat)abstract
- We present the science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems, targeting an evolution in technology, that might lead to impacts and benefits reaching into most areas of society. This roadmap was developed within the framework of the European Graphene Flagship and outlines the main targets and research areas as best understood at the start of this ambitious project. We provide an overview of the key aspects of graphene and related materials (GRMs), ranging from fundamental research challenges to a variety of applications in a large number of sectors, highlighting the steps necessary to take GRMs from a state of raw potential to a point where they might revolutionize multiple industries. We also define an extensive list of acronyms in an effort to standardize the nomenclature in this emerging field.
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| 2. |
- Janssen, Tjbm, et al.
(författare)
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Anomalously strong pinning of the filling factor nu=2 in epitaxial graphene
- 2011
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Ingår i: Physical Review B - Condensed Matter and Materials Physics. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 83:23, s. 233402-
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Tidskriftsartikel (refereegranskat)abstract
- We explore the robust quantization of the Hall resistance in epitaxial graphene grown on Si-terminated SiC. Uniquely to this system, the dominance of quantum over classical capacitance in the charge transfer between the substrate and graphene is such that Landau levels (in particular, the one at exactly zero energy) remain completely filled over an extraordinarily broad range of magnetic fields. One important implication of this pinning of the filling factor is that the system can sustain a very high nondissipative current. This makes epitaxial graphene ideally suited for quantum resistance metrology, and we have achieved a precision of 3 parts in 1010 in the Hall resistance-quantization measurements.
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| 3. |
- Janssen, T J B M, et al.
(författare)
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Graphene, universality of the quantum Hall effect and redefinition of the SI system
- 2011
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Ingår i: New Journal of Physics. - : Institute of Physics. - 1367-2630. ; 13:9, s. 093026-
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Tidskriftsartikel (refereegranskat)abstract
- The Systeme Internationale dunites (SI) is about to undergo its biggest change in half a century by redefining the units for mass and current in terms of the fundamental constants h and e, respectively. This change crucially relies on the exactness of the relationships that link these constants to measurable quantities. Here we report the first direct comparison of the integer quantum Hall effect (QHE) in epitaxial graphene with that in GaAs/AlGaAs heterostructures. We find no difference in the quantized resistance value within the relative standard uncertainty of our measurement of 8.6 x 10(-11), this being the most stringent test of the universality of the QHE in terms of material independence.
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| 4. |
- Janssen, T J B M, et al.
(författare)
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Precision comparison of the quantum Hall effect in graphene and gallium arsenide
- 2012
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Ingår i: Metrologia. - : Institute of Physics. - 0026-1394 .- 1681-7575. ; 49:3, s. 294-306
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Tidskriftsartikel (refereegranskat)abstract
- The half-integer quantum Hall effect in epitaxial graphene is compared with high precision to the well-known integer effect in a GaAs/AlGaAs heterostructure. We find no difference between the quantized resistance values within the relative standard uncertainty of our measurement of 8.7 x 10(-11). The result places new tighter limits on any possible correction terms to the simple relation R-K = h/e(2), and also demonstrates that epitaxial graphene samples are suitable for application as electrical resistance standards of the highest metrological quality. We discuss the characterization of the graphene sample used in this experiment and present the details of the cryogenic current comparator bridge and associated uncertainty budget.
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| 5. |
- Chua, C., et al.
(författare)
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Quantum Hall Effect and Quantum Point Contact in Bilayer-Patched Epitaxial Graphene
- 2014
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 14:6, s. 3369-3373
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Tidskriftsartikel (refereegranskat)abstract
- We study an epitaxial graphene monolayer with bilayer inclusions via magnetotransport measurements and scanning gate microscopy at low temperatures. We find that bilayer inclusions can be metallic or insulating depending on the initial and gated carrier density. The metallic bilayers act as equipotential shorts for edge currents, while closely spaced insulating bilayers guide the flow of electrons in the monolayer constriction, which was locally gated using a scanning gate probe.
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| 6. |
- Kukushkin, I. V., et al.
(författare)
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New type of B-periodic magneto-oscillations in a two-dimensional electron system induced by microwave irradiation
- 2004
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 92:23, s. 236803-1
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Tidskriftsartikel (refereegranskat)abstract
- A B-periodic magnetotransport oscillation in GaAs/AlGaAs quantum wells was reported. The oscillations were induced by microwave radiation and were periodic in magnetic field. The period was determined by the electron density, the microwave frequency and the distance between potential probes. It was found that the phenomenon was accounted for by interference of coherently excited edge magnetoplasmons in the contact regions and offers perspectives for developing new tunable microwave and terahertz detection schemes and spectroscopic techniques.
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| 7. |
- Lara Avila, Samuel, 1983, et al.
(författare)
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Influence of Impurity Spin Dynamics on Quantum Transport in Epitaxial Graphene
- 2015
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Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 1079-7114 .- 0031-9007. ; 115:10, s. 106602-
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Tidskriftsartikel (refereegranskat)abstract
- Experimental evidence from both spin-valve and quantum transport measurements points towards unexpectedly fast spin relaxation in graphene. We report magnetotransport studies of epitaxial graphene on SiC in a vector magnetic field showing that spin relaxation, detected using weak-localization analysis, is suppressed by an in-plane magnetic field B-parallel to, and thereby proving that it is caused at least in part by spinful scatterers. A nonmonotonic dependence of the effective decoherence rate on B-parallel to reveals the intricate role of the scatterers' spin dynamics in forming the interference correction to the conductivity, an effect that has gone unnoticed in earlier weak localization studies.
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| 8. |
- Lara Avila, Samuel, 1983, et al.
(författare)
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Non-Volatile Photochemical Gating of an Epitaxial Graphene/Polymer Heterostructure
- 2011
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Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 23:7, s. 878-
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Tidskriftsartikel (refereegranskat)abstract
- A novel heterostructure based on epitaxial graphene grown on silicon carbide combined with two polymers is demonstrated, with a neutral spacer and a photoactive layer that provides potent electron acceptors under UV light exposure. UV exposure of this heterostructure enables control of the electrical parameters of graphene in a non-invasive, non-volatile, and reversible way.
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| 9. |
- Gottselig, N., et al.
(författare)
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Elemental Composition of Natural Nanoparticles and Fine Colloids in European Forest Stream Waters and Their Role as Phosphorus Carriers
- 2017
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Ingår i: Global Biogeochemical Cycles. - 0886-6236 .- 1944-9224. ; 31:10, s. 1592-1607
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Tidskriftsartikel (refereegranskat)abstract
- Biogeochemical cycling of elements largely occurs in dissolved state, but many elements may also be bound to natural nanoparticles (NNP, 1-100 nm) and fine colloids (100-450 nm). We examined the hypothesis that the size and composition of stream water NNP and colloids vary systematically across Europe. To test this hypothesis, 96 stream water samples were simultaneously collected in 26 forested headwater catchments along two transects across Europe. Three size fractions (~1-20 nm, >20-60 nm, and >60 nm) of NNP and fine colloids were identified with Field Flow Fractionation coupled to inductively coupled plasma mass spectrometry and an organic carbon detector. The results showed that NNP and fine colloids constituted between 2 ± 5% (Si) and 53 ± 21% (Fe; mean ± SD) of total element concentrations, indicating a substantial contribution of particles to element transport in these European streams, especially for P and Fe. The particulate contents of Fe, Al, and organic C were correlated to their total element concentrations, but those of particulate Si, Mn, P, and Ca were not. The fine colloidal fractions >60 nm were dominated by clay minerals across all sites. The resulting element patterns of NNP <60 nm changed from North to South Europe from Fe- to Ca-dominated particles, along with associated changes in acidity, forest type, and dominant lithology.
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| 10. |
- Janssen, Tjbm, et al.
(författare)
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Breakdown of the quantum Hall effect in graphene
- 2012
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Ingår i: CPEM Digest (Conference on Precision Electromagnetic Measurements). - 0589-1485. - 9781467304399 ; , s. 510-511
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Konferensbidrag (refereegranskat)abstract
- We present experimental details on the carrier density dependent breakdown current in epitaxial graphene grown on SiC. We show that in this system even at very low carrier densities and moderate temperatures it is still possible to have a breakdown current large enough for metrologically accurate quantum Hall resistance measurements. This work paves the way for a simple bench top/turnkey quantum resistance standard.
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| 11. |
- Janssen, Tjbm, et al.
(författare)
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Practical and Fundamental Impact of Epitaxial Graphene on Quantum Metrology
- 2013
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Ingår i: Mapan - Journal of Metrology Society of India. - : Springer Science and Business Media LLC. - 0970-3950 .- 0974-9853. ; 28:4, s. 239-250
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Forskningsöversikt (refereegranskat)abstract
- The discovery 8 years ago of the quantum Hall effect (QHE) in graphene sparked an immediate interest in the metrological community. Here was a material which was completely different from commonly used semiconductor systems and which seemed to have some uniques properties which could make it ideally suited for high-precision resistance metrology. However, measuring the QHE in graphene turned out to be not so simple as first thought. In particular the small size of exfoliated graphene samples made precision measurements difficult. This dramatically changed with the development of large-area graphene grown on SiC and in this short review paper we discuss the journey from first observation to the highest-ever precision comparison of the QHE.
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| 12. |
- Janssen, Tjbm, et al.
(författare)
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Quantum resistance metrology using graphene
- 2013
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Ingår i: Reports on Progress in Physics. - : IOP Publishing. - 0034-4885 .- 1361-6633. ; 76:10
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we review the recent extraordinary progress in the development of a new quantum standard for resistance based on graphene. We discuss the unique properties of this material system relating to resistance metrology and discuss results of the recent highest-ever precision direct comparison of the Hall resistance between graphene and traditional GaAs. We mainly focus our review on graphene expitaxially grown on SiC, a system which so far resulted in the best results. We also briefly discuss progress in the two other graphene material systems, exfoliated graphene and chemical vapour deposition graphene, and make a critical comparison with SiC graphene. Finally, we discuss other possible applications of graphene in metrology.
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| 13. |
- Kinaret, Jari, 1962, et al.
(författare)
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Graphene-driven revolutions in ICT and beyond
- 2011
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Ingår i: Procedia Computer Science, 2nd European Future Technologies Conference and Exhibition 2011, FET 11, Budapest; 4 May through 6 May 2011. - : Elsevier BV. - 1877-0509. ; 7, s. 30-33
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Konferensbidrag (refereegranskat)abstract
- This session described the FET Flagship Pilot on graphene and related two-dimensional materials. The flagship targets a revolution in information and communication technology, with impacts reaching into other areas of the society. The session featured four talks on the scientific and technological potential and open research challenges within the scope of the proposed flagship, industrial view on possibilities and challenges posed by graphene and related materials, and presentation on the implementation and structure of the flagship pilot.
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| 14. |
- Kopylov, S., et al.
(författare)
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Charge transfer between epitaxial graphene and silicon carbide
- 2010
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 97:11
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Tidskriftsartikel (refereegranskat)abstract
- We analyze doping of graphene grown on SiC in two models which differ by the source of charge transferred to graphene, namely, from SiC surface and from bulk donors. For each of the two models, we find the maximum electron density induced in monolayer and bilayer graphene, which is determined by the difference between the work function for electrons in pristine graphene and donor states on/in SiC, and analyze the responsivity of graphene to the density variation by means of electrostatic gates.
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| 15. |
- Lara Avila, Samuel, 1983, et al.
(författare)
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Disordered Fermi Liquid in Epitaxial Graphene from Quantum Transport Measurements
- 2011
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 107:16, s. 166602-
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Tidskriftsartikel (refereegranskat)abstract
- We have performed magnetotransport measurements on monolayer epitaxial graphene and analyzed them in the framework of the disordered Fermi liquid theory. We have separated the electron-electron and weak-localization contributions to resistivity and demonstrated the phase coherence over a micrometer length scale, setting the limit of at least 50 ps on the spin relaxation time in this material.
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| 16. |
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| 17. |
- Tzalenchuk, A.Y., et al.
(författare)
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Graphene and the universality of the quantum Hall effect
- 2013
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Ingår i: Proceedings of the International School of Physics "Enrico Fermi". - 1879-8195 .- 0074-784X. - 9781614993254 ; 185, s. 323-350
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Konferensbidrag (refereegranskat)abstract
- The quantum Hall effect allows the standard for resistance to be defined in terms of the elementary charge and Planck's constant alone. The effect comprises the quantization of the Hall resistance in two-dimensional electron systems in rational fractions of RK=h/e2=25812.8074434(84) Ω (Mohr P. J. et al., Rev. Mod. Phys., 84 (2012) 1527), the resistance quantum. Despite 30 years of research into the quantum Hall effect, the level of precision necessary for metrology, a few parts per billion, has been achieved only in silicon and III-V heterostructure devices. In this lecture we show that graphene - a single layer of carbon atoms - beats these well-established semiconductor materials as the system of choice for the realisation of the quantum resistance standard. Here we shall briefly describe graphene technology, discuss the structure and electronic properties of graphene, including the unconventional quantum Hall effect and then present in detail the route, which led to the most precise quantum Hall resistance universality test ever performed. © Società Italiana di Fisica.
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| 18. |
- Tzalenchuk, A.Y., et al.
(författare)
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Towards a quantum resistance standard based on epitaxial graphene
- 2010
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Ingår i: Nature Nanotechnology. - 1748-3387 .- 1748-3395. ; 5:3, s. 186-189
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Tidskriftsartikel (refereegranskat)abstract
- The quantum Hall effect(1) allows the international standard for resistance to be defined in terms of the electron charge and Planck's constant alone. The effect comprises the quantization of the Hall resistance in two-dimensional electron systems in rational fractions of R-K = h/e(2) = 25 812.807 557(18) Omega, the resistance quantum(2). Despite 30 years of research into the quantum Hall effect, the level of precision necessary for metrology-a few parts per billion-has been achieved only in silicon and III-V heterostructure devices(3-5). Graphene should, in principle, be an ideal material for a quantum resistance standard(6), because it is inherently two-dimensional and its discrete electron energy levels in a magnetic field (the Landau levels(7)) are widely spaced. However, the precisions demonstrated so far have been lower than one part per million(8). Here, we report a quantum Hall resistance quantization accuracy of three parts per billion in monolayer epitaxial graphene at 300 mK, four orders of magnitude better than previously reported. Moreover, by demonstrating the structural integrity and uniformity of graphene over hundreds of micrometres, as well as reproducible mobility and carrier concentrations across a half-centimetre wafer, these results boost the prospects of using epitaxial graphene in applications beyond quantum metrology.
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