SwePub - search: WFRF:(Lara Avila Samuel 1983)

Enumeration	Reference	Cover	Find
1.	Yager, Thomas, 1987, et al. (author) Express Optical Analysis of Epitaxial Graphene on SiC: Impact of Morphology on Quantum Transport 2013 In: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 13:9, s. 4217-4223 Journal article (peer-reviewed)abstract We show that inspection with an optical microscope allows surprisingly simple and accurate identification of single and multilayer graphene domains in epitaxial graphene on silicon carbide (SiC/G) and is informative about nanoscopic details of the SiC topography, making it ideal for rapid and noninvasive quality control of as-grown SiC/G. As an illustration of the power of the method, we apply it to demonstrate the correlations between graphene morphology and its electronic properties by quantum magneto-transport.
2.	Alexander-Webber, J. A., et al. (author) Phase Space for the Breakdown of the Quantum Hall Effect in Epitaxial Graphene 2013 In: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 111:9, s. e096601- Journal article (peer-reviewed)abstract We report the phase space defined by the quantum Hall effect breakdown in polymer gated epitaxial graphene on SiC (SiC/G) as a function of temperature, current, carrier density, and magnetic fields up to 30 T. At 2 K, breakdown currents (Ic) almost 2 orders of magnitude greater than in GaAs devices are observed. The phase boundary of the dissipationless state (ρxx=0) shows a [1-(T/Tc)2] dependence and persists up to Tc>45 K at 29 T. With magnetic field Ic was found to increase ∝B3/2 and Tc∝B2. As the Fermi energy approaches the Dirac point, the ν=2 quantized Hall plateau appears continuously from fields as low as 1 T up to at least 19 T due to a strong magnetic field dependence of the carrier density.
3.	Baker, A M R, et al. (author) Energy loss rates of hot Dirac fermions in epitaxial, exfoliated, and CVD graphene 2013 In: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X .- 2469-9950 .- 2469-9969. ; 87:4, s. 045414- Journal article (peer-reviewed)abstract Energy loss rates for hot carriers in graphene have been measured using graphene produced by epitaxial growth on SiC, exfoliation, and chemical vapor deposition (CVD). It is shown that the temperature dependence of the energy loss rates measured with high-field damped Shubnikov-de Haas oscillations and the temperature dependence of the weak localization peak close to zero field correlate well, with the high-field measurements understating the energy loss rates by similar to 40% compared to the low-field results. The energy loss rates for all graphene samples follow a universal scaling of T-e(4) at low temperatures and depend weakly on carrier density proportional to n(-1/2), evidence for enhancement of the energy loss rate due to disorder in CVD samples.
4.	Baker, A M R, et al. (author) Weak localization scattering lengths in epitaxial, and CVD graphene 2012 In: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X .- 2469-9950 .- 2469-9969. ; 86:23, s. 235441- Journal article (peer-reviewed)abstract Weak localization in graphene is studied as a function of carrier density in the range from 1 x 10(11) cm(-2) to 1.43 x 10(13) cm(-2) using devices produced by epitaxial growth onto SiC and CVD growth on thin metal film. The magnetic field dependent weak localization is found to be well fitted by theory, which is then used to analyze the dependence of the scattering lengths L-phi, L-i, and L-* on carrier density. We find no significant carrier dependence for L-phi, a weak decrease for L-i with increasing carrier density just beyond a large standard error, and a n(-1/4) dependence for L-*. We demonstrate that currents as low as 0.01 nA are required in smaller devices to avoid hot-electron artifacts in measurements of the quantum corrections to conductivity. DOI: 10.1103/PhysRevB.86.235441
5.	Broman, S. L., et al. (author) Dihydroazulene Photoswitch Operating in Sequential Tunneling Regime: Synthesis and Single-Molecule Junction Studies 2012 In: Advanced Functional Materials. - : Wiley. - 1616-3028 .- 1616-301X. ; 22:20, s. 4249-4258 Journal article (peer-reviewed)abstract Molecular switches play a central role for the development of molecular electronics. In this work it is demonstrated that the reproducibility and robustness of a single-molecule dihydroazulene (DHA)/vinylheptafulvene (VHF) switch can be remarkably enhanced if the switching kernel is weakly coupled to electrodes so that the electron transport goes by sequential tunneling. To assure weak coupling, the DHA switching kernel is modified by incorporating p-MeSC6H4 end-groups. Molecules are prepared by Suzuki cross-couplings on suitable halogenated derivatives of DHA. The synthesis presents an expansion of our previously reported brominationeliminationcross-coupling protocol for functionalization of the DHA core. For all new derivatives the kinetics of DHA/VHF transition has been thoroughly studied in solution. The kinetics reveals the effect of sulfur end-groups on the thermal ring-closure of VHF. One derivative, incorporating a p-MeSC6H4 anchoring group in one end, has been placed in a silver nanogap. Conductance measurements justify that transport through both DHA (high resistivity) and VHF (low resistivity) forms goes by sequential tunneling. The switching is fairly reversible and reenterable; after more than 20 ON-OFF switchings, both DHA and VHF forms are still recognizable, albeit noticeably different from the original states.
6.	Chua, C., et al. (author) Quantum Hall Effect and Quantum Point Contact in Bilayer-Patched Epitaxial Graphene 2014 In: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 14:6, s. 3369-3373 Journal article (peer-reviewed)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.
7.	Drexler, C., et al. (author) Magnetic quantum ratchet effect in graphene 2013 In: Nature Nanotechnology. - 1748-3387 .- 1748-3395. ; 8:2, s. 104-107 Journal article (peer-reviewed)abstract A periodically driven system with spatial asymmetry can exhibit a directed motion facilitated by thermal or quantum fluctuations(1). This so-called ratchet effect(2) has fascinating ramifications in engineering and natural sciences(3-18). Graphene(19) is nominally a symmetric system. Driven by a periodic electric field, no directed electric current should flow. However, if the graphene has lost its spatial symmetry due to its substrate or adatoms, an electronic ratchet motion can arise. We report an experimental demonstration of such an electronic ratchet in graphene layers, proving the underlying spatial asymmetry. The orbital asymmetry of the Dirac fermions is induced by an in-plane magnetic field, whereas the periodic driving comes from terahertz radiation. The resulting magnetic quantum ratchet transforms the a.c. power into a d.c. current, extracting work from the out-of-equilibrium electrons driven by undirected periodic forces. The observation of ratchet transport in this purest possible two-dimensional system indicates that the orbital effects may appear and be substantial in other two-dimensional crystals such as boron nitride, molybdenum dichalcogenides and related heterostructures. The measurable orbital effects in the presence of an in-plane magnetic field provide strong evidence for the existence of structure inversion asymmetry in graphene.
8.	Drexler, C., et al. (author) Reststrahlen Band assisted photocurrents in graphene 2013 In: International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz. - 2162-2027 .- 2162-2035. - 9781467347174 Conference paper (peer-reviewed)abstract We report on the experimental and theoretical study of the Reststrahlen Band assisted photocurrents in epitaxial grown graphene on SiC. We show that excitation of graphene with infrared radiation results in a dc current. We demonstrate that photocurrent in response to linearly polarized radiation exhibit a resonance enhancement in the frequency range of the Reststrahlen Band of the SiC substrate. By contrast the photocurrent excited by circularly polarized radiation is suppressed in the same spectral range. The developed theory is in agreement with the data and reveals a strong influence of the Reststrahl Band on the high frequency transport in graphene.
9.	Eless, V, et al. (author) Phase coherence and energy relaxation in epitaxial graphene under microwave radiation 2013 In: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 103:9 Journal article (peer-reviewed)abstract We have performed low-temperature magnetotransport measurements on monolayer epitaxial graphene under microwave radiation and extracted the radiation-induced effective temperatures, energy relaxation, and the dephasing times. We established that the response of the graphene sample is entirely bolometric at least up to 170 GHz. Dynamic dephasing, i.e., the time-reversal symmetry breaking effect of the ac electromagnetic field rather than mediated by heating, may become significant in the terahertz frequency range and in samples with longer phase coherence time.
10.	Fernandez, Yuri A. Diaz, 1978, et al. (author) The conquest of middle-earth: combining top-down and bottom-up nanofabrication for constructing nanoparticle based devices 2014 In: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 6:24, s. 14605-14616 Journal article (peer-reviewed)abstract The development of top-down nanofabrication techniques has opened many possibilities for the design and realization of complex devices based on single molecule phenomena such as e. g. single molecule electronic devices. These impressive achievements have been complemented by the fundamental understanding of self-assembly phenomena, leading to bottom-up strategies to obtain hybrid nanomaterials that can be used as building blocks for more complex structures. In this feature article we highlight some relevant published work as well as present new experimental results, illustrating the versatility of self-assembly methods combined with top-down fabrication techniques for solving relevant challenges in modern nanotechnology. We present recent developments on the use of hierarchical self-assembly methods to bridge the gap between sub-nanometer and micrometer length scales. By the use of non-covalent self-assembly methods, we show that we are able to control the positioning of nanoparticles on surfaces, and to address the deterministic assembly of nano-devices with potential applications in plasmonic sensing and single-molecule electronics experiments.
11.	Ganichev, S.D., et al. (author) Magnetic quantum ratchet effect in graphene 2013 In: International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz. - 2162-2027 .- 2162-2035. - 9781467347174 Conference paper (peer-reviewed)abstract We report on the observation of magnetic quantum ratchet (MQR) effect induced by electric field of terahertz radiation in single-layer graphene samples subjected to an inplane magnetic field. We show that the dc electric current stems from the orbital asymmetry of the Dirac fermions induced by an in-plane magnetic field, while the periodic driving comes from terahertz radiation. A microscopic theory of the observed effect is developed being in a good qualitative agreement with the experiment. The observation of the ratchet transport in the purest possible two-dimensional system indicates that the orbital effects may appear and be substantial in other 2D crystals, such as boron nitride, molybdenum dichalcogenides, and related heterostructures. The measurable orbital effects in the presence of an in-plane magnetic field give strong evidence for the existence of structure inversion asymmetry in graphene.
12.	Jain, T., et al. (author) Aligned Growth of Gold Nanorods in PMMA Channels: Parallel Preparation of Nanogaps 2012 In: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 6:5, s. 3861-3867 Journal article (peer-reviewed)abstract We demonstrate alignment and positional control of gold nanorods grown in situ on substrates using a seed-mediated synthetic approach. Alignment control is obtained by directing the growth of spherical nanoparticle seeds into nanorods in well-defined poly(methyl methacrylate) nanochannels. Substrates with prepatterned metallic electrodes provide an additional handle for the position of the gold nanorods and yield nanometer-sized gaps between the electrode and nanorod. The presented approach is a novel demonstration of bottom-up device fabrication of multiple nanogap junctions on a single chip mediated via in situ growth of gold nanorods acting as nanoelectrodes.
13.	Janssen, Tjbm, et al. (author) Anomalously strong pinning of the filling factor nu=2 in epitaxial graphene 2011 In: Physical Review B - Condensed Matter and Materials Physics. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 83:23, s. 233402- Journal article (peer-reviewed)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.
14.	Janssen, Tjbm, et al. (author) Breakdown of the quantum Hall effect in graphene 2012 In: CPEM Digest (Conference on Precision Electromagnetic Measurements). - 0589-1485. - 9781467304399 ; , s. 510-511 Conference paper (peer-reviewed)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.
15.	Janssen, T J B M, et al. (author) Graphene, universality of the quantum Hall effect and redefinition of the SI system 2011 In: New Journal of Physics. - : Institute of Physics. - 1367-2630. ; 13:9, s. 093026- Journal article (peer-reviewed)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.
16.	Janssen, T J B M, et al. (author) Precision comparison of the quantum Hall effect in graphene and gallium arsenide 2012 In: Metrologia. - : Institute of Physics. - 0026-1394 .- 1681-7575. ; 49:3, s. 294-306 Journal article (peer-reviewed)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.
17.	Janssen, Tjbm, et al. (author) Practical and Fundamental Impact of Epitaxial Graphene on Quantum Metrology 2013 In: Mapan - Journal of Metrology Society of India. - : Springer Science and Business Media LLC. - 0970-3950 .- 0974-9853. ; 28:4, s. 239-250 Research review (peer-reviewed)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.
18.	Janssen, Tjbm, et al. (author) Quantum resistance metrology using graphene 2013 In: Reports on Progress in Physics. - : IOP Publishing. - 0034-4885 .- 1361-6633. ; 76:10 Journal article (peer-reviewed)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.
19.	Jiang, C. Y., et al. (author) Helicity-dependent photocurrents in graphene layers excited by midinfrared radiation of a CO2 laser 2011 In: Physical Review B - Condensed Matter and Materials Physics. - : American Physical Society. - 2469-9950 .- 2469-9969 .- 1098-0121 .- 1550-235X. ; 84:12 Journal article (peer-reviewed)abstract We report the study of the helicity-driven photocurrents in graphene excited by midinfrared light of a CO(2) laser. Illuminating an unbiased monolayer sheet of graphene with circularly polarized radiation generates-under oblique incidence-an electric current perpendicular to the plane of incidence, whose sign is reversed by switching the radiation helicity. We show that the current is caused by the interplay of the circular ac Hall effect and the circular photogalvanic effect. By studying the frequency dependence of the current in graphene layers grown on the SiC substrate, we observe that the current exhibits a resonance at frequencies matching the longitudinal optical phonon in SiC.
20.	Karch, J., et al. (author) Dynamic Hall Effect Driven by Circularly Polarized Light in a Graphene Layer 2010 In: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 105:22, s. 227402- Journal article (peer-reviewed)abstract We report the observation of the circular ac Hall effect where the current is solely driven by the crossed ac electric and magnetic fields of circularly polarized radiation. Illuminating an unbiased monolayer sheet of graphene with circularly polarized terahertz radiation at room temperature generates-under oblique incidence-an electric current perpendicular to the plane of incidence, whose sign is reversed by switching the radiation helicity. Alike the classical dc Hall effect, the voltage is caused by crossed E and B fields which are, however rotating with the lights frequency.
21.	Karch, J., et al. (author) Terahertz Radiation Driven Chiral Edge Currents in Graphene 2011 In: Physical Review Letters. - : American Physical Society. - 1079-7114 .- 0031-9007. ; 107:27 Journal article (peer-reviewed)abstract We observe photocurrents induced in single-layer graphene samples by illumination of the graphene edges with circularly polarized terahertz radiation at normal incidence. The photocurrent flows along the sample edges and forms a vortex. Its winding direction reverses by switching the light helicity from left to right handed. We demonstrate that the photocurrent stems from the sample edges, which reduce the spatial symmetry and result in an asymmetric scattering of carriers driven by the radiation electric field. The developed theory based on Boltzmann's kinetic equation is in a good agreement with the experiment. We show that the edge photocurrents can be applied for determination of the conductivity type and the momentum scattering time of the charge carriers in the graphene edge vicinity.
22.	Lara Avila, Samuel, 1983, et al. (author) Bianthrone in a Single-Molecule Junction: Conductance Switching with a Bistable Molecule Facilitated by Image Charge Effects 2010 In: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 114:48, s. 20686-20695 Journal article (peer-reviewed)abstract Bianthrone is a sterically hindered compound that exists in the form of two nonplanar isomers. Our experimental study of single-molecule junctions with bianthrone reveals persistent switching of electric conductance at low temperatures, which can be reasonably associated with molecular isomerization events. Temperature dependence of the switching rate allows for an estimate of the activation energy of the process, on the order of 120 +/- 50 meV. Quantum-chemical calculations of the potential energy relief of neutral bianthrone and its anion, including identification of transition states, yields the isolated molecule isomerization barriers too high vs the previous estimate, though compatible with previous experimental studies in solution. Nevertheless, we show that the attraction of the anion in the vicinity of the metal surface by its image charge can change the energetic landscape, in particular, by significantly reducing the barrier to values compatible with the observed switching behavior.
23.	Lara Avila, Samuel, 1983, et al. (author) Disordered Fermi Liquid in Epitaxial Graphene from Quantum Transport Measurements 2011 In: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 107:16, s. 166602- Journal article (peer-reviewed)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.
24.	Lara Avila, Samuel, 1983, et al. (author) Light-Triggered Conductance Switching in Single-Molecule Dihydroazulene/Vinylheptafulvene Junctions 2011 In: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 115:37, s. 18372-18377 Journal article (peer-reviewed)abstract Derivatives of 1,1-dicyano-1,8a-dihydroazulene (DHA) undergo light-induced ring-opening to a corresponding vinylheptafulvene (VHF), which in turn is thermally reverted to DHA. Here we have fabricated single-molecule DHA/VHF junctions and measured light-triggered conductance switching of these junctions. The DHA/VHF system studied includes a substituent group at the seven-membered ring. Light-induced conversion of this DHA to VHF in the junction is supported by a reduced tunnelling gap in tunnelling density of states. In fact, the reduced tunnelling gap corresponds to the reduced HOMO-LUMO gap of VHF relative to that of DHA as measured by absorption spectroscopy and electrochemistry. For this comparison, electrochemical measurements were performed on both the parent DHA/VHF system and the functionalized system that was subject to transport measurements. In one junction, it was possible to switch back and forth between DHA and VHF three times, the forward reaction being induced by light and the back-reaction occurring after waiting a period of time.
25.	Lara Avila, Samuel, 1983 (author) Magnetotransport characterization of epitaxial graphene on SiC 2012 Doctoral thesis (other academic/artistic)abstract Low-temperature magnetotransport is used to characterize graphene grown epitaxially on the silicon face of 4H silicon carbide (SiC/G). Observation of half-integer quantum Hall effect (QHE) in large Hall bars, patterned across several terraces of the SiC substrate, suggest that monolayer graphene grows continuously over defects.Complete characterization was possible using carrier density control technologies developed for SiC/G, including organic dielectrics, photochemical gating and a solid electrolyte. The photochemical gating with organic polymers, achieved by using a spacer layer directly in contact with graphene that protects its integrity, followed by a layer that responds to light, is envisioned as a prototypical architecture for the development of graphene-based sensors.Fine details of electron scattering were found through measurement of quantum corrections to the conductivity of SiC/G, arising from weak localization (WL) and electron-electron interactions (E-E). It was found that scattering is determined by charged impurities under graphene, while the effect of terraces is proposed to manifests as intervalley scattering. The extracted temperature dependence of the decoherence rate allowed to identify E-E interactions and to suggest spin-flip centers as sources ofdephasing in the system. The analysis of WL provided an indirect measurement of the spin relaxation time in SiC/G, at the level of 50 ps.Altogether, this work contributed to develop the first application in which graphene outperforms conventional semiconducors, in the field of quantum metrology. The half integer QHE in SiC/G is proposed as standard for electrical resistance to replace GaAs heterostructures. A direct comparison with the QHE in GaAs, the most strict universality test of the QHE ever performed, supports the hypothesis that the electrical resistance is quantized in units of h/e2, with an uncertainty of 0.084 parts per billion. The accuracy of the comparison was limited by the critical current in the GaAs sample, 4 times lower than in the SiC/G sample.
26.	Lara Avila, Samuel, 1983, et al. (author) Non-Volatile Photochemical Gating of an Epitaxial Graphene/Polymer Heterostructure 2011 In: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 23:7, s. 878- Journal article (peer-reviewed)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.
27.	Lartsev, Arseniy, 1987, et al. (author) Tuning carrier density across Dirac point in epitaxial graphene on SiC by corona discharge 2014 In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 105:6 Journal article (peer-reviewed)abstract We demonstrate reversible carrier density control across the Dirac point (Δ n∼ 1013cm-2) in epitaxial graphene on SiC (SiC/G) via high electrostatic potential gating with ions produced by corona discharge. The method is attractive for applications where graphene with a fixed carrier density is needed, such as quantum metrology, and more generally as a simple method of gating 2DEGs formed at semiconductor interfaces and in topological insulators.
28.	Olbrich, P., et al. (author) Reststrahl band-assisted photocurrents in epitaxial graphene layers 2013 In: Physical Review B - Condensed Matter and Materials Physics. - : American Physical Society. - 2469-9950 .- 2469-9969 .- 1098-0121 .- 1550-235X. ; 88:24, s. 7- Journal article (peer-reviewed)abstract We report on the observation of the reststrahl band-assisted photocurrents in epitaxial graphene on SiC excited by infrared radiation. The peculiar spectral dependence for frequencies lying within the reststrahl band of the SiC substrate provides a direct and noninvasive way to probe the electric field magnitude at atomic distances from the material's surface. Furthermore our results reveal that nonlinear optical and optoelectronic phenomena in two-dimensional crystals and other atomic scale structures can be giantly enhanced by their deposition on a substrate with negative dielectric constant.
29.	Sun, Lanlan, 1981, et al. (author) Single-molecule electronics: from chemical design to functional devices 2014 In: Chemical Society Reviews. - 1460-4744 .- 0306-0012. ; 43:21, s. 7378-7411 Research review (peer-reviewed)abstract The use of single molecules in electronics represents the next limit of miniaturisation of electronic devices, which would enable us to continue the trend of aggressive downscaling of silicon-based electronic devices. More significantly, the fabrication, understanding and control of fully functional circuits at the single-molecule level could also open up the possibility of using molecules as devices with novel, not-foreseen functionalities beyond complementary metal-oxide semiconductor technology (CMOS). This review aims at highlighting the chemical design and synthesis of single molecule devices as well as their electrical and structural characterization, including a historical overview and the developments during the last 5 years. We discuss experimental techniques for fabrication of single-molecule junctions, the potential application of single-molecule junctions as molecular switches, and general physical phenomena in single-molecule electronic devices.
30.	Tzalenchuk, Alexander, et al. (author) Engineering and metrology of epitaxial graphene 2011 In: Solid State Communications. - : Elsevier. - 0038-1098 .- 1879-2766. ; 151:16, s. 1094-1099 Journal article (peer-reviewed)abstract ere we review the concepts and technologies, in particular photochemical gating, which contributed to the recent progress in quantum Hall resistance metrology based on large scale epitaxial graphene on silicon carbide.
31.	Tzalenchuk, A.Y., et al. (author) Graphene and the universality of the quantum Hall effect 2013 In: Proceedings of the International School of Physics "Enrico Fermi". - 1879-8195 .- 0074-784X. - 9781614993254 ; 185, s. 323-350 Conference paper (peer-reviewed)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.
32.	Tzalenchuk, A.Y., et al. (author) Towards a quantum resistance standard based on epitaxial graphene 2010 In: Nature Nanotechnology. - 1748-3387 .- 1748-3395. ; 5:3, s. 186-189 Journal article (peer-reviewed)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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