| 1. |
- Apell, Peter, 1952, et al.
(författare)
-
Edge plasmons in graphene nanostructures
- 2011
-
Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 84:8
-
Tidskriftsartikel (refereegranskat)abstract
- Plasmon modes in graphene are influenced by the unusual dispersion relation of the material. For bulk plasmons this results in a n(1/4) dependence of the plasma frequency on the charge density, as opposed to the n(1/2) dependence in two-dimensional electron gas (2DEG); yet, bulk plasmon dispersion in graphene follows a similar q(1/2) behavior as for other two-dimensional materials. In this work we consider finite graphene nanostructures, semi-infinite sheets, and circular disks and study edge plasmons that are confined to the boundaries of the structures. We find that, for abrupt edges, graphene edge plasmons behave analogously to those in 2DEGs, but, for gradual edge profiles, important distinctions arise. In particular, we show that for a linear edge profile, graphene supports fewer edge modes than a 2DEG at a given q, and the edge monopole plasmon dispersion in graphene follows a q(1/4) law in contrast to the q(0) behavior seen in 2DEGs. RAMOWITZ M, 1964
|
|
| 2. |
- Atalaya, Juan, 1981, et al.
(författare)
-
Elasticity theory for graphene membranes
- 2010
-
Ingår i: Adsorption and Phase Behaviour in Nanochannels and Nanotubes. - Dordrecht : Springer Netherlands. - 9789048124800 ; , s. 273-290
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Starting from an atomistic approach we have derived a hierarchy of successively more simplified continuum elasticity descriptions for modeling the mechanical properties of suspended graphene sheets. We find that already for deflections of the order of 0.5∈Å a theory that correctly accounts for nonlinearities is necessary and that for many purposes a set of coupled Duffing-type equations may be used to accurately describe the dynamics of graphene membranes. The descriptions are validated by applying them to square graphene-based resonators with clamped edges and studying numerically their mechanical responses. Both static and dynamic responses are treated, and we find good agreement with recent experimental findings. © 2010 Springer Science+Business Media B.V.
|
|
| 3. |
- Atalaya, Juan, 1981, et al.
(författare)
-
Nanomechanical mass measurement using nonlinear response of a graphene membrane
- 2010
-
Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 91:4
-
Tidskriftsartikel (refereegranskat)abstract
- We propose a scheme to measure the mass of a single particle using the nonlinear response of a 2D nanoresonator with degenerate eigenmodes. Using numerical and analytical calculations, we show that by driving a square graphene nanoresonator into the nonlinear regime, simultaneous determination of the mass and position of an added particle is possible. Moreover, this scheme only requires measurements in a narrow frequency band near the fundamental resonance.
|
|
| 4. |
- Croy, Alexander, 1981, et al.
(författare)
-
Nonlinear damping in graphene resonators
- 2012
-
Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 86:23, s. Article Number: 235435-
-
Tidskriftsartikel (refereegranskat)abstract
- Based on a continuum mechanical model for single-layer graphene, we propose and analyze a microscopic mechanism for dissipation in nanoelectromechanical graphene resonators. We find that coupling between flexural modes and in-plane phonons leads to linear and nonlinear damping of out-of-plane vibrations. By tuning external parameters such as bias and ac voltages, one can cross over from a linear-to a nonlinear-damping dominated regime. We discuss the behavior of the effective quality factor in this context. DOI: 10.1103/PhysRevB.86.235435
|
|
| 5. |
- Kaunisto, R., et al.
(författare)
-
Nanotube Device
- 2010
-
Patent (övrigt vetenskapligt/konstnärligt)
|
|
| 6. |
- Kinaret, Jari, 1962, et al.
(författare)
-
Graphene-driven revolutions in ICT and beyond
- 2011
-
Ingår i: Procedia Computer Science, 2nd European Future Technologies Conference and Exhibition 2011, FET 11, Budapest; 4 May through 6 May 2011. - : Elsevier BV. - 1877-0509. ; 7, s. 30-33
-
Konferensbidrag (refereegranskat)abstract
- This session described the FET Flagship Pilot on graphene and related two-dimensional materials. The flagship targets a revolution in information and communication technology, with impacts reaching into other areas of the society. The session featured four talks on the scientific and technological potential and open research challenges within the scope of the proposed flagship, industrial view on possibilities and challenges posed by graphene and related materials, and presentation on the implementation and structure of the flagship pilot.
|
|
| 7. |
- Midtvedt, Daniel, 1988, et al.
(författare)
-
Parametric Resonance in Nanoelectromechanical Single Electron Transistors
- 2011
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 11:4, s. 1439-1442
-
Tidskriftsartikel (refereegranskat)abstract
- We show that the coupling between single-electron charging and mechanical motion in a nanoelectromechanical single-electron transistor can be utilized in a novel parametric actuation scheme. This scheme, which relies on a periodic modulation of the mechanical resonance frequency through an alternating source drain voltage, leads to a parametric instability and emergence of mechanical vibrations in a limited range of modulation amplitudes. Remarkably, the frequency range where instability occurs and the maximum oscillation amplitude, depend weakly on the damping in the system. We also show that a weak parametric modulation increases the effective quality factor and amplifies the system's response to the conventional actuation that exploits an AC gate signal.
|
|
| 8. |
|
|
| 9. |
- Rehammar, Robert, 1980, et al.
(författare)
-
Carbon nanofiber-based photonic crystals – fabrication, diffraction and ellipsometry investigations
- 2011
-
Ingår i: Carbon-Based Electronic Devices - Processing, Performance and Reliability. - : Materials Research Society. - 0272-9172. - 9781618394996 ; , s. 28-33
-
Konferensbidrag (refereegranskat)abstract
- Carbon nanofibers were used as building blocks for two-dimensional photonic crystal slabs. Electron beam lithography and chemical vapor deposition were used to fabricate regular arrays and random patterns of nanofibers. The optical properties of the samples were investigated using a diffraction measurement setup, as well as reflection ellipsometry. We find that carbon nanofiber regularity has a strong effect on both diffractive and specular optical properties. This shows that ellipsometry can be a valuable tool to study properties of carbon nanofiber arrays. It also shows that carbon nanofibers provide an interesting candidate as building blocks for nanostructured optical components.
|
|
| 10. |
- Rehammar, Robert, 1980, et al.
(författare)
-
Diffraction from carbon nanofiber arrays
- 2012
-
Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 37:1, s. 100-102
-
Tidskriftsartikel (refereegranskat)abstract
- We fabricate a square planar photonic crystal (PC) from carbon nanofibres (CNFs) using e-beam lithography and chemical vapour deposition and investigate the optical properties of this system. The system exhibit diffraction that is well described by diffraction theory. We measure the intensity of the (-1,0) and (-1,-1) diffraction spots as functions of angle of incidence. The radiation diagram obtained can be explained by interference between different diffraction beams. We observe a polarisation dependence of the intensity. In conclusion we suggest future applications of these structures.
|
|
| 11. |
- Rehammar, Robert, 1980, et al.
(författare)
-
Electromechanically Tunable Carbon Nanofiber Photonic Crystal
- 2013
-
Ingår i: Nano letters (Print). - : AMER CHEMICAL SOC. - 1530-6984 .- 1530-6992. ; 13:2, s. 397-401
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate an electrically tunable 2D photonic crystal array constructed from vertically alignedcarbon nanofibers. The nanofibers are actuated by applying a voltage between adjacent carbon nanofiberpairs grown directly on metal electrodes, thus dynamically changing the form factor of the photoniccrystal lattice. The change in optical properties is characterised using optical diffraction andellipsometry. The experimental results are shown to be in agreement with theoretical predictions andprovide a proof-of-principle for rapidly switchable photonic crystals operating in the visible that can befabricated using standard nanolithography techniques combined with plasma CVD growth of thenanofibers.
|
|
| 12. |
- Rehammar, Robert, 1980, et al.
(författare)
-
Optical properties of carbon nanofiber photonic crystals
- 2010
-
Ingår i: NANOTECHNOLOGY. - : Institute of Physics; 1999. - 0957-4484 .- 1361-6528. ; 21:46, s. 465203-
-
Tidskriftsartikel (refereegranskat)abstract
- Carbon nanofibers (CNFs) are used as components of planar photonic crystals. Square and rectangular lattices and random patterns of vertically aligned CNFs were fabricated and their properties studied using ellipsometry. We show that detailed information such as symmetry directions and the band structure of these novel materials can be extracted from considerations of the polarization state in the specular beam. The refractive index of the individual nanofibers was found to be n(CNF) = 4.1.
|
|
| 13. |
- Svensson, Johannes, et al.
(författare)
-
Carbon Nanotube Field Effect Transistors with Suspended Graphene Gates
- 2011
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 11:9, s. 3569-3575
-
Tidskriftsartikel (refereegranskat)abstract
- Novel field effect transistors with suspended graphene gates are demonstrated. By incorporating mechanical motion of the gate electrode, it is possible to improve the switching characteristics compared to a static gate, as shown by a combination of experimental measurements and numerical simulations. The mechanical motion of the graphene gate is confirmed by using atomic force microscopy to directly measure the electrostatic deflection. The device geometry investigated here can also provide a sensitive measurement technique for detecting high-frequency motion of suspended membranes as required, e.g., for mass sensing.
|
|
| 14. |
- Viefers, Susanne, 1970, et al.
(författare)
-
ELECTROMECHANICAL NANOTUBE TUNNELING DEVICE COMPRISING SOURCE, DRAIN AND GATE
- 2011
-
Patent (övrigt vetenskapligt/konstnärligt)abstract
- The present invention relates to a nanotube device (100) comprising a nanotube with a longitudinal and a lateral extension, a structure for supporting at least a first part of the nanotube, and first means for exerting a force upon the nanotube in a first direction defined by its lateral extension. At least a second part of the nanotube protrudes beyond the support of said structure, so that when said force exceeds a certain level, the second part of the nanotube will flex in the direction of its lateral extension, and thereby close a first electrical circuit. Suitably, the first means for exerting said force upon the nanotube is an electrical means, the force being created by applying a voltage to the means. The device allows for quantum mechanics tunnel effects, both at a source and at a drain electrode.
|
|
| 15. |
- Voje, Aurora, 1985, et al.
(författare)
-
Generating macroscopic superposition states in nanomechanical graphene resonators
- 2012
-
Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 85:20
-
Tidskriftsartikel (refereegranskat)abstract
- A theoretical study of the quantum dynamics of a symmetric nanomechanical graphene resonator with degenerate flexural modes is presented. Applying voltage pulses to two back gates, flexural vibrations of the membrane can be selectively actuated and manipulated. For graphene, nonlinear response becomes important for amplitudes comparable to the magnitude of zero-point fluctuations. We show, using analytical and numerical methods, that this allows for creation of catlike superpositions of coherent states as well as superpositions of coherent catlike nonproduct states.
|
|
| 16. |
- Wang, Weihua, 1981, et al.
(författare)
-
Edge magnetoplasmons and the optical excitations in graphene disks
- 2012
-
Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 86:12
-
Tidskriftsartikel (refereegranskat)abstract
- We discuss the edge magnetoplasmon properties in highly doped graphene disks, and the corresponding optical excitations. Edge magnetoplasmons with nonzero angular momentum (l not equal 0) have two branches corresponding to different edge current rotations with respect to the magnetic field. The resonance energies of one branch are blueshifted and the other redshifted relative to energies at B = 0, with the energy differences linearly proportional to the magnetic field. Recently, the l = 1 dipole mode has been investigated by two experiments using optical transmission spectroscopy [Crassee et al., Nano Lett. 12, 2470 (2012); Yan et al., ibid. 12, 3766 (2012)], and classical cyclotron resonances were found in highly doped graphene samples. These are determined by graphene magneto-optical conductivities, which behave like a conventional two-dimensional electron system in the high doping limit.
|
|
| 17. |
- Wang, Weihua, 1981, et al.
(författare)
-
Excitation of edge magnetoplasmons in semi-infinite graphene sheets: Temperature effects
- 2012
-
Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 85:23, s. art. no. 235444-
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate edge magnetoplasmons in semi-infinite graphene sheets. Similar to an ordinary two-dimensional electron system (2DES), at zero temperature graphene sheets exhibit two magnetoplasmon branches, a higher-energy one starting at the n = 1 Landau level (cyclotron frequency) and a lower-energy edge branch starting at zero frequency. However, in contrast to a 2DES with parabolic dispersion, at nonzero temperatures an extra magnetoplasmon branch arises at the n = 1 Landau level and has the same edge current rotation as the lower-energy branch.
|
|
| 18. |
- Wang, Weihua, 1981, et al.
(författare)
-
Plasmons in graphene nanoribbons: Interband transitions and nonlocal effects
- 2013
-
Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 87:19
-
Tidskriftsartikel (refereegranskat)abstract
- We study plasmon excitations in infinitely long graphene nanoribbons using a quasistatic approach, where one-dimensional coupled equations for electrostatic potential and excited charge density are derived in the transverse direction. By incorporating a hydrodynamical description of the excited charge density, we investigate nonlocal effects in plasmon excitations. Moreover, the method presented here provides means to look into the nonlocal plasmon response in more complex graphene nanostructures such as wedges. We find that the plasmon frequencies are lowered by interband transitions and raised due to nonlocal effects. The frequency shifts depend monotonically on the dielectric constant of the surrounding medium. Most importantly, the nonlocal effects can strongly affect the excited charge density at the edges. Finally, we show that a larger increase of dipolar plasmon frequencies occurs in smaller graphene nanoribbons as expected.
|
|
