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

Numrering	Referens	Omslagsbild	Hitta
1.	Boschi, Alex, et al. (författare) Mesoscopic 3D Charge Transport in Solution-Processed Graphene-Based Thin Films: A Multiscale Analysis 2023 Ingår i: Small. - 1613-6810 .- 1613-6829. ; 19:42 Tidskriftsartikel (refereegranskat)abstract Graphene and related 2D material (GRM) thin films consist of 3D assembly of billions of 2D nanosheets randomly distributed and interacting via van der Waals forces. Their complexity and the multiscale nature yield a wide variety of electrical characteristics ranging from doped semiconductor to glassy metals depending on the crystalline quality of the nanosheets, their specific structural organization ant the operating temperature. Here, the charge transport (CT) mechanisms are studied that are occurring in GRM thin films near the metal-insulator transition (MIT) highlighting the role of defect density and local arrangement of the nanosheets. Two prototypical nanosheet types are compared, i.e., 2D reduced graphene oxide and few-layer-thick electrochemically exfoliated graphene flakes, forming thin films with comparable composition, morphology and room temperature conductivity, but different defect density and crystallinity. By investigating their structure, morphology, and the dependence of their electrical conductivity on temperature, noise and magnetic-field, a general model is developed describing the multiscale nature of CT in GRM thin films in terms of hopping among mesoscopic bricks, i.e., grains. The results suggest a general approach to describe disordered van der Waals thin films.
2.	Shaali, Mehrnaz, 1981, et al. (författare) Site-selective immobilization of functionalized DNA origami on nanopatterned Teflon AF 2017 Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry (RSC). - 2050-7526 .- 2050-7534. ; 5:30, s. 7637-7643 Tidskriftsartikel (refereegranskat)abstract We demonstrate the use of arrays of Teflon AF nanopillars for directing the assembly of single rectangular DNA origami scaffolds, functionalized with covalently linked fluorophore molecules, in defined positions on patterned surfaces. This is achieved by introducing Teflon AF as a non-amplified negative e-beam resist, which is exposed and chemically developed to generate arrays of hydrophobic nanopillars with a minimum feature size 40 nm. Binding of the DNA origami to the pillars is facilitated by porphyrin moieties that act as hydrophobic molecular anchors, reaching 80% coverage of the available sites. This combination of top-down lithography and bottom-up self assembly is an efficient means of fabricating hierarchically structured bio-nanointerfaces in which the positioning of functional units is precisely controlled on the molecular scale inside the DNA assembly, and on the nanoscale at pre-designed locations on the substrate.
3.	Shetty, Naveen, 1988, et al. (författare) Scalable Fabrication of Edge Contacts to 2D Materials : Implications for Quantum Resistance Metrology and 2D Electronics 2023 Ingår i: ACS Applied Nano Materials. - : American Chemical Society. - 2574-0970. ; 6:7, s. 6292- Tidskriftsartikel (refereegranskat)abstract We report a reliable and scalable fabrication method for producing electrical contacts to two-dimensional (2D) materials based on the tri-layer resist system. We demonstrate the applicability of this method in devices fabricated on epitaxial graphene on silicon carbide (epigraphene) used as a scalable 2D material platform. For epigraphene, data on nearly 70 contacts result in median values of the one-dimensional (1D) specific contact resistances ρc ∼ 67 Ω·μm and follow the Landauer quantum limit ρc ∼ n-1/2, consistently reaching values ρc < 50 Ω·μm at high carrier densityn. As a proof of concept, we apply the same fabrication method to the transition metal dichalcogenide (TMDC) molybdenum disulfide (MoS2). Our edge contacts enable MoS2 field-effect transistor (FET) behavior with an ON/OFF ratio of >106 at room temperature (>109 at cryogenic temperatures). The fabrication route demonstrated here allows for contact metallization using thermal evaporation and also by sputtering, giving an additional flexibility when designing electrical interfaces, which is key in practical devices and when exploring the electrical properties of emerging materials. © 2023 The Authors.
4.	Yager, Thomas, 1987, et al. (författare) Express Optical Analysis of Epitaxial Graphene on SiC: Impact of Morphology on Quantum Transport 2013 Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 13:9, s. 4217-4223 Tidskriftsartikel (refereegranskat)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.
5.	Acharya, Narendra, 1982, et al. (författare) MgB 2 HEB terahertz mixers: Diffusion- or phonon- cooled? 2019 Ingår i: ISSTT 2019 - 30th International Symposium on Space Terahertz Technology, Proceedings Book. ; , s. 101- Konferensbidrag (refereegranskat)
6.	Alexander-Webber, J. A., et al. (författare) Giant quantum Hall plateaus generated by charge transfer in epitaxial graphene 2016 Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 6 Tidskriftsartikel (refereegranskat)abstract Epitaxial graphene has proven itself to be the best candidate for quantum electrical resistance standards due to its wide quantum Hall plateaus with exceptionally high breakdown currents. However one key underlying mechanism, a magnetic field dependent charge transfer process, is yet to be fully understood. Here we report measurements of the quantum Hall effect in epitaxial graphene showing the widest quantum Hall plateau observed to date extending over 50 T, attributed to an almost linear increase in carrier density with magnetic field. This behaviour is strong evidence for field dependent charge transfer from charge reservoirs with exceptionally high densities of states in close proximity to the graphene. Using a realistic framework of broadened Landau levels we model the densities of donor states and predict the field dependence of charge transfer in excellent agreement with experimental results, thus providing a guide towards engineering epitaxial graphene for applications such as quantum metrology.
7.	Alexander-Webber, J. A., et al. (författare) Phase Space for the Breakdown of the Quantum Hall Effect in Epitaxial Graphene 2013 Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 111:9, s. e096601- Tidskriftsartikel (refereegranskat)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.
8.	Andzane, J., et al. (författare) Effect of graphene substrate type on formation of Bi 2 Se 3 nanoplates 2019 Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 9:1 Tidskriftsartikel (refereegranskat)abstract Knowledge of nucleation and further growth of Bi 2 Se 3 nanoplates on different substrates is crucial for obtaining ultrathin nanostructures and films of this material by physical vapour deposition technique. In this work, Bi 2 Se 3 nanoplates were deposited under the same experimental conditions on different types of graphene substrates (as-transferred and post-annealed chemical vapour deposition grown monolayer graphene, monolayer graphene grown on silicon carbide substrate). Dimensions of the nanoplates deposited on graphene substrates were compared with the dimensions of the nanoplates deposited on mechanically exfoliated mica and highly ordered pyrolytic graphite flakes used as reference substrates. The influence of different graphene substrates on nucleation and further lateral and vertical growth of the Bi 2 Se 3 nanoplates is analysed. Possibility to obtain ultrathin Bi 2 Se 3 thin films on these substrates is evaluated. Between the substrates considered in this work, graphene grown on silicon carbide is found to be the most promising substrate for obtaining of 1–5 nm thick Bi 2 Se 3 films.
9.	Baker, A M R, et al. (författare) Energy loss rates of hot Dirac fermions in epitaxial, exfoliated, and CVD graphene 2013 Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X .- 2469-9950 .- 2469-9969. ; 87:4, s. 045414- Tidskriftsartikel (refereegranskat)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.
10.	Baker, A M R, et al. (författare) Weak localization scattering lengths in epitaxial, and CVD graphene 2012 Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X .- 2469-9950 .- 2469-9969. ; 86:23, s. 235441- Tidskriftsartikel (refereegranskat)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
11.	Broman, S. L., et al. (författare) Dihydroazulene Photoswitch Operating in Sequential Tunneling Regime: Synthesis and Single-Molecule Junction Studies 2012 Ingår i: Advanced Functional Materials. - : Wiley. - 1616-3028 .- 1616-301X. ; 22:20, s. 4249-4258 Tidskriftsartikel (refereegranskat)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.
12.	Charaev, Ilya, et al. (författare) Single-photon detection using large-scale high-temperature MgB 2 sensors at 20 K 2024 Ingår i: Nature Communications. - 2041-1723 .- 2041-1723. ; 15:1 Tidskriftsartikel (refereegranskat)abstract Ultra-fast single-photon detectors with high current density and operating temperature can benefit space and ground applications, including quantum optical communication systems, lightweight cryogenics for space crafts, and medical use. Here we demonstrate magnesium diboride (MgB2) thin-film superconducting microwires capable of single-photon detection at 1.55 μm optical wavelength. We used helium ions to alter the properties of MgB2, resulting in microwire-based detectors exhibiting single-photon sensitivity across a broad temperature range of up to 20 K, and detection efficiency saturation for 1 μm wide microwires at 3.7 K. Linearity of detection rate vs incident power was preserved up to at least 100 Mcps. Despite the large active area of up to 400 × 400 μm2, the reset time was found to be as low as ~ 1 ns. Our research provides possibilities for breaking the operating temperature limit and maximum single-pixel count rate, expanding the detector area, and raises inquiries about the fundamental mechanisms of single-photon detection in high-critical-temperature superconductors.
13.	Cherednichenko, Serguei, 1970, et al. (författare) Quantum transport at Dirac point enables graphene for terahertz heterodyne astronomy 2019 Ingår i: ISSTT 2019 - 30th International Symposium on Space Terahertz Technology, Proceedings Book. - : International Symposium on Space Terahertz Technology. ; , s. 236- Konferensbidrag (refereegranskat)
14.	Chua, C., et al. (författare) Quantum Hall Effect and Quantum Point Contact in Bilayer-Patched Epitaxial Graphene 2014 Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 14:6, s. 3369-3373 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.
15.	Çlnar, Mustafa Neşet, et al. (författare) Toward Optimized Charge Transport in Multilayer Reduced Graphene Oxides 2022 Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 22:6, s. 2202-2208 Tidskriftsartikel (refereegranskat)abstract In the context of graphene-based composite applications, a complete understanding of charge conduction in multilayer reduced graphene oxides (rGO) is highly desirable. However, these rGO compounds are characterized by multiple and different sources of disorder depending on the chemical method used for their synthesis. Most importantly, the precise role of interlayer interaction in promoting or jeopardizing electronic flow remains unclear. Here, thanks to the development of a multiscale computational approach combining first-principles calculations with large-scale transport simulations, the transport scaling laws in multilayer rGO are unraveled, explaining why diffusion worsens with increasing film thickness. In contrast, contacted films are found to exhibit an opposite trend when the mean free path becomes shorter than the channel length, since conduction becomes predominantly driven by interlayer hopping. These predictions are favorably compared with experimental data and open a road toward the optimization of graphene-based composites with improved electrical conduction.
16.	Drexler, C., et al. (författare) Magnetic quantum ratchet effect in graphene 2013 Ingår i: Nature Nanotechnology. - 1748-3387 .- 1748-3395. ; 8:2, s. 104-107 Tidskriftsartikel (refereegranskat)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.
17.	Drexler, C., et al. (författare) Reststrahlen Band assisted photocurrents in graphene 2013 Ingår i: International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz. - 2162-2027 .- 2162-2035. - 9781467347174 Konferensbidrag (refereegranskat)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.
18.	Eklöf, Johnas, 1988, et al. (författare) Controlling deposition of nanoparticles by tuning surface charge of SiO2 by surface modifications 2016 Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 6:106, s. 104246-104253 Tidskriftsartikel (refereegranskat)abstract The self-assembly of nanoparticles on substrates is relevant for a variety of applications such as plasmonics, sensing devices and nanometer-sized electronics. We investigate the deposition of 60 nm spherical Au nanoparticles onto silicon dioxide (SiO2) substrates by changing the chemical treatment of the substrate and by that altering the surface charge. The deposition is characterized by scanning electron microscopy (SEM). Kelvin probe force microscopy (KPFM) was used to characterize the surface workfunction. The underlying physics involved in the deposition of nanoparticles was described by a model based on Derjaguin–Landau–Verwey–Overbeek (DLVO) theory combined with random sequential adsorption (RSA). The spatial statistical method Ripley's K-function was used to verify the DLVO–RSA model (ERSA). The statistical results also showed that the adhered particles exhibit a short-range order at distances below ~300 nm. This method can be used in future research to predict the deposition densities of charged nanoparticles onto charged surfaces.
19.	Eklöf, Johnas, 1988, et al. (författare) Guided selective deposition of nanoparticles by tuning of the surface potential 2017 Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 119:1 Tidskriftsartikel (refereegranskat)abstract Guided deposition of nanoparticles onto different substrates is of great importance for a variety of applications such as biosensing, targeted cancer therapy, anti-bacterial coatings and single molecular electronics. It is therefore important to gain an understanding of what parameters are involved in the deposition of nanoparticles. In this work we have deposited 60 nm, negatively charged, citrate stabilized gold nanoparticles onto microstructures consisting of six different materials, (vanadium (V), silicon dioxide (SiO2), gold (Au), aluminum (Al), copper (Cu) and nickel (Ni)). The samples have then been investigated by scanning electron microscopy to extract the particle density. The surface potential was calculated from the measured surface charge density maps measured by atomic force microscopy while the samples were submerged in a KCl water solution. These values were compared with literature values of the isoelectric points (IEP) of different oxides formed on the metals in an ambient environment. According to measurements, Al had the highest surface potential followed by Ni and Cu. The same trend was observed for the nanoparticle densities. No particles were found on V, SiO2 and Au. The literature values of the IEP showed a different trend compared to the surface potential measurements concluding that IEP is not a reliable parameter for the prediction of NP deposition.
20.	Eless, V, et al. (författare) Phase coherence and energy relaxation in epitaxial graphene under microwave radiation 2013 Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 103:9 Tidskriftsartikel (refereegranskat)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.
21.	Fabbri, Filippo, et al. (författare) Silicene nanosheets intercalated in slightly defective epitaxial graphene on a 4H-SiC(0001) substrate 2022 Ingår i: Surfaces and Interfaces. - : Elsevier BV. - 2468-0230. ; 33 Tidskriftsartikel (refereegranskat)abstract In the last years, epitaxial graphene (epi-Gr) demonstrated to be an excellent substrate for the synthesis of epitaxial or intercalated two dimensional (2D) materials. Among 2D materials, silicene has been for a long time a dream for the scientific community, for its importance both from the fundamental and the application point of view. Despite the theoretical prediction of silicene energetic viability, experimentally the substrate proved to play a fundamental role in the Si atom adsorption process leading, in case of metal substrates, to a mixed phase formation and, for van der Waals chemical inert substrates, to Si atom intercalation even at room temperature. Such an intercalation has been associated to the presence of surface defects. Very recently it has been shown that hundreds of nanometer area quasi-free standing silicene can be grown on top of an almost ideal epi-Gr layer synthesized on 6H-SiC substrate. In the present paper, using scanning tunneling microscopy and Raman analysis, we demonstrate that a non-ideal (slightly defective) epi-Gr network obtained by thermal decomposition of Si-terminated 4H-SiC(0001) enables the Si atom penetration forming intercalated silicene nanosheets at room temperature, thus opening a path towards controlled intercalation of silicon atoms through epi-Gr and formation of silicene nanosheets for future applications in nanotechnology.
22.	Fernandez, Yuri A. Diaz, 1978, et al. (författare) The conquest of middle-earth: combining top-down and bottom-up nanofabrication for constructing nanoparticle based devices 2014 Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 6:24, s. 14605-14616 Tidskriftsartikel (refereegranskat)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.
23.	Ganichev, S.D., et al. (författare) Magnetic quantum ratchet effect in graphene 2013 Ingår i: International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz. - 2162-2027 .- 2162-2035. - 9781467347174 Konferensbidrag (refereegranskat)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.
24.	Geskin, V., et al. (författare) Bianthrone at a Metal Surface: Conductance Switching with a Bistable Molecule Made Feasible by Image Charge Effects 2015 Ingår i: AIP Conference Proceedings. - : AIP Publishing LLC. - 1551-7616 .- 0094-243X. ; 1642, s. 469-472 Konferensbidrag (refereegranskat)abstract Bianthrone is a sterically hindered compound that exists in the form of two non-planar isomers. Our experimental study of single-molecule junctions with bianthrone reveals persistent switching of electric conductance at low temperatures, which can be reasonably associated to molecular isomerization events. Temperature dependence of the switching rate allows for an estimate of the activation energy of the process, on the order of 35-90 meV. Quantum-chemical calculations of the potential surface of neutral bianthrone and its anion, including identification of transition states, yields the isolated molecule isomerization barriers too high vs. the previous estimate, though in perfect agreement 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 significantly alter the energetic landscape, in particular, by reducing the barrier to the values compatible with the observed switching behavior.
25.	Ghasemi, Shima, 1993, et al. (författare) Exploring the impact of select anchor groups for norbornadiene/quadricyclane single-molecule switches 2023 Ingår i: Journal of Materials Chemistry C. - 2050-7534 .- 2050-7526. ; 11:44, s. 15379-15776 Tidskriftsartikel (refereegranskat)abstract To achieve the ultimate limit of device miniaturization, it is necessary to have a comprehensive understanding of the structure–property relationship in functional molecular systems used in single-molecule electronics. This study reports the synthesis and characterization of a novel series of norbornadiene derivatives capped with thioether and thioester anchor groups. Utilizing the mechanically controllable break junction technique, the impact of these capping groups on conductance across single-molecule junctions is investigated. Among the selection of anchor groups, norbornadiene capped with thioacetate and tert-butyl groups exhibits higher conductance (G ≈ 4 × 10−4 G0) compared to methyl thioether (G ≈ 2 × 10−4 G0). Electronic transmission through the considered set of single-molecule junctions has been simulated. The computational results for electron transport across these junctions align closely with the experimental findings, with the thioacetate- and tert-butyl-substituted systems outperforming the methyl thioether-capped derivative. In terms of junction stability, the methyl thioether-capped system is the most resilient, maintaining consistent conductance even after approximately 10 000 cycles. Meanwhile, the likelihood of observing molecular plateaus in both the thioacetate- and tert-butyl-substituted systems declines over time. These findings substantially advance both the design and understanding of functional molecular systems in the realm of single-molecule electronics, particularly in the context of molecular photoswitches.
26.	He, Hans, et al. (författare) Accurate graphene quantum Hall arrays for the new International System of Units 2022 Ingår i: Nature Communications. - : Nature Research. - 2041-1723. ; 13:1 Tidskriftsartikel (refereegranskat)abstract Graphene quantum Hall effect (QHE) resistance standards have the potential to provide superior realizations of three key units in the new International System of Units (SI): the ohm, the ampere, and the kilogram (Kibble Balance). However, these prospects require different resistance values than practically achievable in single graphene devices (~12.9 kΩ), and they need bias currents two orders of magnitude higher than typical breakdown currents IC ~ 100 μA. Here we present experiments on quantization accuracy of a 236-element quantum Hall array (QHA), demonstrating RK/236 ≈ 109 Ω with 0.2 part-per-billion (nΩ/Ω) accuracy with IC ≥ 5 mA (~1 nΩ/Ω accuracy for IC = 8.5 mA), using epitaxial graphene on silicon carbide (epigraphene). The array accuracy, comparable to the most precise universality tests of QHE, together with the scalability and reliability of this approach, pave the road for wider use of graphene in the new SI and beyond. © 2022, The Author(s).
27.	He, Hans, 1989, et al. (författare) Fabrication of graphene quantum hall resistance standard in a cryogen-Table-Top system 2016 Ingår i: 2016 Conference on Precision Electromagnetic Measurements, CPEM 2016; The Westin OttawaOttawa; Canada; 10-15 July 2016. - : Institute of Electrical and Electronics Engineers Inc.. - 9781467391344 ; , s. Art no 7540516- Konferensbidrag (refereegranskat)abstract We have demonstrated quantum Hall resistance measurements with metrological accuracy in a relatively easy to use and compact cryogen-free system operating at a temperature of around 3.8 K and magnetic field below 5 T. This advance in technology is due to the unique properties of epitaxial graphene on silicon carbide (SiC) which lifts the stringent requirements for quantum hall effect seen in conventional semiconductors. This paper presents the processes involved in fabrication and characterization of metrologically viable epitaxial graphene samples.
28.	He, Hans, et al. (författare) Highly efficient UV detection in a metal-semiconductor-metal detector with epigraphene 2022 Ingår i: Applied Physics Letters. - : American Institute of Physics Inc.. - 0003-6951 .- 1077-3118. ; 120:19 Tidskriftsartikel (refereegranskat)abstract We show that epitaxial graphene on silicon carbide (epigraphene) grown at high temperatures (T >1850 °C) readily acts as material for implementing solar-blind ultraviolet (UV) detectors with outstanding performance. We present centimeter-sized epigraphene metal-semiconductor-metal (MSM) detectors with a peak external quantum efficiency of η ∼85% for wavelengths λ = 250-280 nm, corresponding to nearly 100% internal quantum efficiency when accounting for reflection losses. Zero bias operation is possible in asymmetric devices, with the responsivity to UV remaining as high as R = 134 mA/W, making this a self-powered detector. The low dark currents Io ∼50 fA translate into an estimated record high specific detectivity D = 3.5 × 1015 Jones. The performance that we demonstrate, together with material reproducibility, renders epigraphene technologically attractive to implement high-performance planar MSM devices with a low processing effort, including multi-pixel UV sensor arrays, suitable for a number of practical applications. © 2022 Author(s).
29.	He, Hans, et al. (författare) Polymer-encapsulated molecular doped epigraphene for quantum resistance metrology 2019 Ingår i: Metrologia. - : Institute of Physics Publishing. - 0026-1394 .- 1681-7575. ; 56:4 Tidskriftsartikel (refereegranskat)abstract One of the aspirations of quantum metrology is to deliver primary standards directly to end-users thereby significantly shortening the traceability chains and enabling more accurate products. Epitaxial graphene grown on silicon carbide (epigraphene) is known to be a viable candidate for a primary realisation of a quantum Hall resistance standard, surpassing conventional semiconductor two-dimensional electron gases, such as those based on GaAs, in terms of performance at higher temperatures and lower magnetic fields. The bottleneck in the realisation of a turn-key quantum resistance standard requiring minimum user intervention has so far been the need to fine-tune the carrier density in this material to fit the constraints imposed by a simple cryo-magnetic system. Previously demonstrated methods, such as via photo-chemistry or corona discharge, require application prior to every cool-down as well as specialist knowledge and equipment. To this end we perform metrological evaluation of epigraphene with carrier density tuned by a recently reported permanent molecular doping technique. Measurements at two National Metrology Institutes confirm accurate resistance quantisation below 5n-1. Furthermore, samples show no significant drift in carrier concentration and performance on multiple thermal cycles over three years. This development paves the way for dissemination of primary resistance standards based on epigraphene
30.	He, Hans, et al. (författare) Stable and Tunable Charge Carrier Control of Graphene for Quantum Resistance Metrology 2018 Ingår i: 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018). - : IEEE. - 9781538609736 - 9781538609743 Konferensbidrag (refereegranskat)abstract Here we demonstrate a stable and tunable method to alter the carrier concentration of epitaxial graphene grown on silicon carbide. This technique relies on chemical doping by an acceptor molecule. Through careful tuning one can produce chemically doped graphene quantum resistance devices which show long-term stability in ambient conditions and have performance comparable to that of GaAs quantum resistance standards. This development paves the way for controlled device fabrication of graphene quantum hall resistance standards, which can be reliably tailored to operate below 5 T and above 4 K out-of-the-box, without further adjustments from the end-user.
31.	He, Hans, 1989, et al. (författare) The performance limits of epigraphene Hall sensors doped across the Dirac point 2020 Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 116:22 Tidskriftsartikel (refereegranskat)abstract Epitaxial graphene on silicon carbide, or epigraphene, provides an excellent platform for Hall sensing devices in terms of both high electrical quality and scalability. However, the challenge in controlling its carrier density has thus far prevented systematic studies of epigraphene Hall sensor performance. In this work, we investigate epigraphene Hall sensors where epigraphene is doped across the Dirac point using molecular doping. Depending on the carrier density, molecular-doped epigraphene Hall sensors reach room temperature sensitivities of S-V=0.23V/(VT) and S-I=1440V/(AT), with magnetic field detection limits down to B-MIN=27 nT/root Hz at 20kHz. Thermally stabilized devices demonstrate operation up to 150 degrees C with S-V=0.12V/(VT), S-I=300V/(AT), and B-MIN similar to 100 nT/root Hz at 20kHz. Our work demonstrates that epigraphene doped close to the Dirac point could potentially outperform III-V Hall elements in the extended and military temperature ranges.
32.	He, Hans, 1989, et al. (författare) Uniform doping of graphene close to the Dirac point by polymer-assisted assembly of molecular dopants 2018 Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 9:1 Tidskriftsartikel (refereegranskat)abstract Tuning the charge carrier density of two-dimensional (2D) materials by incorporating dopants into the crystal lattice is a challenging task. An attractive alternative is the surface transfer doping by adsorption of molecules on 2D crystals, which can lead to ordered molecular arrays. However, such systems, demonstrated in ultra-high vacuum conditions (UHV), are often unstable in ambient conditions. Here we show that air-stable doping of epitaxial graphene on SiC—achieved by spin-coating deposition of 2,3,5,6-tetrafluoro-tetracyano-quino-dimethane (F4TCNQ) incorporated in poly(methyl-methacrylate)—proceeds via the spontaneous accumulation of dopants at the graphene-polymer interface and by the formation of a charge-transfer complex that yields low-disorder, charge-neutral, large-area graphene with carrier mobilities ~70 000 cm2V−1s−1at cryogenic temperatures. The assembly of dopants on 2D materials assisted by a polymer matrix, demonstrated by spin-coating wafer-scale substrates in ambient conditions, opens up a scalable technological route toward expanding the functionality of 2D materials.
33.	Hinrichs, Karsten, et al. (författare) Field Manipulation of Band Properties in Infrared Spectra of Thin Films 2023 Ingår i: ADVANCED PHOTONICS RESEARCH. - 2699-9293. ; In Press Tidskriftsartikel (refereegranskat)abstract This comprehensive optical study analyzes field manipulations of bands in infrared (IR) spectra of thin films and functional surfaces for varying measurement and sample conditions. Band variations related to the materials dielectric functions, the measurement geometry, the film thickness as well as the direction dependence of the probing electromagnetic fields are demonstrated. Examples are discussed for isotropic polymer films (approximate to 200 nm polymethylmethacrylate [PMMA]) on gold and silicon as well as an anisotropic hydrogen monolayer on a Si(111) surface, characterized by IR-attenuated total reflection, IR microscopy, and incidence-angle-dependent IR polarimetry. Even for fixed optical material properties, significant manipulations of band frequency and shape (shifts up to approximate to 14 cm-1 for PMMA, up to approximate to 3 cm-1 for H-Si) occur in not only polarization-dependent but also unpolarized spectra. The shown data underline that polarimetric measurements and optical analyses are essential for a detailed interpretation of band shapes. Field manipulations of bands in infrared spectra of thin films and functional surfaces are discussed. Examples are isotropic polymer films on gold and silicon as well as an anisotropic hydrogen monolayer on Si(111). Band variations relate to the materials dielectric functions, the measurement geometry, the film thickness as well as the polarization of the probing electromagnetic fields.image (c) 2023 WILEY-VCH GmbH
34.	Huang, J., et al. (författare) Hot carrier relaxation of Dirac fermions in bilayer epitaxial graphene 2015 Ingår i: Journal of Physics Condensed Matter. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 27:16 Tidskriftsartikel (refereegranskat)abstract Energy relaxation of hot Dirac fermions in bilayer epitaxial graphene is experimentally investigated by magnetotransport measurements on Shubnikov-de Haas oscillations and weak localization. The hot-electron energy loss rate is found to follow the predicted Bloch-Gruneisen power-law behaviour of T-4 at carrier temperatures from 1.4K up to similar to 100 K, due to electron-acoustic phonon interactions with a deformation potential coupling constant of 22 eV. A carrier density dependence n(e)(-1.5) in the scaling of the T-4 power law is observed in bilayer graphene, in contrast to the n(e)(-0.5) dependence in monolayer graphene, leading to a crossover in the energy loss rate as a function of carrier density between these two systems. The electron-phonon relaxation time in bilayer graphene is also shown to be strongly carrier density dependent, while it remains constant for a wide range of carrier densities in monolayer graphene. Our results and comparisons between the bilayer and monolayer exhibit a more comprehensive picture of hot carrier dynamics in graphene systems.
35.	Huang, J., et al. (författare) Physics of a disordered Dirac point in epitaxial graphene from temperature-dependent magnetotransport measurements 2015 Ingår i: Physical Review B - Condensed Matter and Materials Physics. - : American Physical Society. - 2469-9950 .- 2469-9969 .- 1098-0121 .- 1550-235X. ; 92:7 Tidskriftsartikel (refereegranskat)abstract We report a study of disorder effects on epitaxial graphene in the vicinity of the Dirac point by magnetotransport. Hall effect measurements show that the carrier density increases quadratically with temperature, in good agreement with theoretical predictions which take into account intrinsic thermal excitation combined with electron-hole puddles induced by charged impurities. We deduce disorder strengths in the range 10.2-31.2 meV, depending on the sample treatment. We investigate the scattering mechanisms and estimate the impurity density to be 3.0-9.1x10(10) cm(-2) for our samples. A scattering asymmetry for electrons and holes is observed and is consistent with theoretical calculations for graphene on SiC substrates. We also show that the minimum conductivity increases with increasing disorder strength, in good agreement with quantum-mechanical numerical calculations.
36.	Iordanidou, Konstantina, 1989, et al. (författare) Electric Field and Strain Tuning of 2D Semiconductor van der Waals Heterostructures for Tunnel Field-Effect Transistors 2023 Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 15:1, s. 1762-1771 Tidskriftsartikel (refereegranskat)abstract Heterostacks consisting of low-dimensional materials are attractive candidates for future electronic nanodevices in the post-silicon era. In this paper, using first-principles calculations based on density functional theory (DFT), we explore the structural and electronic properties of MoTe2/ZrS2 heterostructures with various stacking patterns and thicknesses. Our simulations show that the valence band (VB) edge of MoTe2 is almost aligned with the conduction band (CB) edge of ZrS2, and (MoTe2)m/(ZrS2)m (m = 1, 2) heterostructures exhibit the long-sought broken gap band alignment, which is pivotal for realizing tunneling transistors. Electrons are found to spontaneously flow from MoTe2 to ZrS2, and the system resembles an ultrascaled parallel plate capacitor with an intrinsic electric field pointed from MoTe2 to ZrS2. The effects of strain and external electric fields on the electronic properties are also investigated. For vertical compressive strains, the charge transfer increases due to the decreased coupling between the layers, whereas tensile strains lead to the opposite behavior. For negative electric fields a transition from the type-III to the type-II band alignment is induced. In contrast, by increasing the positive electric fields, a larger overlap between the valence and conduction bands is observed, leading to a larger band-to-band tunneling (BTBT) current. Low-strained heterostructures with various rotation angles between the constituent layers are also considered. We find only small variations in the energies of the VB and CB edges with respect to the Fermi level, for different rotation angles up to 30°. Overall, our simulations offer insights into the fundamental properties of low-dimensional heterostructures and pave the way for their future application in energy-efficient electronic nanodevices.
37.	Jain, T., et al. (författare) Aligned Growth of Gold Nanorods in PMMA Channels: Parallel Preparation of Nanogaps 2012 Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 6:5, s. 3861-3867 Tidskriftsartikel (refereegranskat)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.
38.	Janssen, Tjbm, et al. (författare) Anomalously strong pinning of the filling factor nu=2 in epitaxial graphene 2011 Ingår i: Physical Review B - Condensed Matter and Materials Physics. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 83:23, s. 233402- 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.
39.	Janssen, Tjbm, et al. (författare) Breakdown of the quantum Hall effect in graphene 2012 Ingår i: CPEM Digest (Conference on Precision Electromagnetic Measurements). - 0589-1485. - 9781467304399 ; , s. 510-511 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.
40.	Janssen, T J B M, et al. (författare) Graphene, universality of the quantum Hall effect and redefinition of the SI system 2011 Ingår i: New Journal of Physics. - : Institute of Physics. - 1367-2630. ; 13:9, s. 093026- 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.
41.	Janssen, T J B M, et al. (författare) Precision comparison of the quantum Hall effect in graphene and gallium arsenide 2012 Ingår i: Metrologia. - : Institute of Physics. - 0026-1394 .- 1681-7575. ; 49:3, s. 294-306 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.
42.	Janssen, Tjbm, et al. (författare) Operation of graphene quantum Hall resistance standard in a cryogen-free table-top system 2015 Ingår i: 2D Materials. - : IOP Publishing. - 2053-1583. ; 2:3, s. 035015- Tidskriftsartikel (refereegranskat)abstract Wedemonstrate quantum Hall resistance measurements with metrological accuracy in a small cryogen-free system operating at a temperature of around 3.8Kand magnetic fields below 5 T. Operating this system requires little experimental knowledge or laboratory infrastructure, thereby greatly advancing the proliferation of primary quantum standards for precision electrical metrology. This significant advance in technology has come about as a result of the unique properties of epitaxial graphene on SiC.
43.	Janssen, Tjbm, et al. (författare) Practical and Fundamental Impact of Epitaxial Graphene on Quantum Metrology 2013 Ingår i: Mapan - Journal of Metrology Society of India. - : Springer Science and Business Media LLC. - 0970-3950 .- 0974-9853. ; 28:4, s. 239-250 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.
44.	Janssen, Tjbm, et al. (författare) Quantum resistance metrology using graphene 2013 Ingår i: Reports on Progress in Physics. - : IOP Publishing. - 0034-4885 .- 1361-6633. ; 76:10 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.
45.	Janssen, Tjbm, et al. (författare) Towards a cryogen-free table-top primary resistance standard 2016 Ingår i: 2016 Conference on Precision Electromagnetic Measurements (Cpem 2016). - : Institute of Electrical and Electronics Engineers Inc.. - 9781467391344 Konferensbidrag (refereegranskat)abstract We demonstrate quantum Hall resistance measurements with metrological accuracy in a small cryogen-free system operating at a temperature of around 3.8 K and magnetic fields below 5 T. We use this system to investigate the optimisation of graphene/SiC devices for maximum breakdown current. In addition we report the first characterisation of a cryogen-free cryogenic current comparator which enables entirely cryogen-free primary resistance metrology.
46.	Jiang, C. Y., et al. (författare) Helicity-dependent photocurrents in graphene layers excited by midinfrared radiation of a CO2 laser 2011 Ingår i: Physical Review B - Condensed Matter and Materials Physics. - : American Physical Society. - 2469-9950 .- 2469-9969 .- 1098-0121 .- 1550-235X. ; 84:12 Tidskriftsartikel (refereegranskat)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.
47.	Jõemetsa, Silver, 1990, et al. (författare) Molecular Lipid Films on Microengineering Materials 2019 Ingår i: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 35:32, s. 10286-10298 Tidskriftsartikel (refereegranskat)abstract In this study, we have systematically investigated the formation of molecular phospholipid films on a variety of solid substrates fabricated from typical surface engineering materials and the fluidic properties of the lipid membranes formed on these substrates. The surface materials comprise of borosilicate glass, mica, SiO2, Al (native oxide), Al2O3, TiO2, ITO, SiC, Au, Teflon AF, SU-8, and graphene. We deposited the lipid films from small unilamellar vesicles (SUVs) by means of an open-space microfluidic device, observed the formation and development of the films by laser scanning confocal microscopy, and evaluated the mode and degree of coverage, fluidity, and integrity. In addition to previously established mechanisms of lipid membrane–surface interaction upon bulk addition of SUVs on solid supports, we observed nontrivial lipid adhesion phenomena, including reverse rolling of spreading bilayers, spontaneous nucleation and growth of multilamellar vesicles, and the formation of intact circular patches of double lipid bilayer membranes. Our findings allow for accurate prediction of membrane–surface interactions in microfabricated devices and experimental environments where model membranes are used as functional biomimetic coatings.
48.	Karch, J., et al. (författare) Dynamic Hall Effect Driven by Circularly Polarized Light in a Graphene Layer 2010 Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 105:22, s. 227402- Tidskriftsartikel (refereegranskat)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.
49.	Karch, J., et al. (författare) Terahertz Radiation Driven Chiral Edge Currents in Graphene 2011 Ingår i: Physical Review Letters. - : American Physical Society. - 1079-7114 .- 0031-9007. ; 107:27 Tidskriftsartikel (refereegranskat)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.
50.	Karimi, Bayan, et al. (författare) Electron-phonon coupling of epigraphene at millikelvin temperatures measured by quantum transport thermometry 2021 Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 118:10 Tidskriftsartikel (refereegranskat)abstract We investigate the basic charge and heat transport properties of charge neutral epigraphene at sub-kelvin temperatures, demonstrating a nearly logarithmic dependence of electrical conductivity over more than two decades in temperature. Using graphene's sheet conductance as an in situ thermometer, we present a measurement of electron-phonon heat transport at mK temperatures and show that it obeys the T4 dependence characteristic for a clean two-dimensional conductor. Based on our measurement, we predict the noise-equivalent power of ∼ 10 - 22 W / Hz of the epigraphene bolometer at the low end of achievable temperatures.

Skapa referenser, mejla, bekava och länka

Länka till träfflistan

Träfflista för sökning "WFRF:(Lara Avila Samuel 1983) "

Avgränsa träffmängd

År