Showing papers by "Fred Schedin published in 2008"

Giant intrinsic carrier mobilities in graphene and its bilayer

Abstract: We have studied temperature dependences of electron transport in graphene and its bilayer and found extremely low electron-phonon scattering rates that set the fundamental limit on possible charge carrier mobilities at room temperature. Our measurements show that mobilities higher than 200 000 cm2/V s are achievable, if extrinsic disorder is eliminated. A sharp (thresholdlike) increase in resistivity observed above approximately 200 K is unexpected but can qualitatively be understood within a model of a rippled graphene sheet in which scattering occurs on intraripple flexural phonons.

Chaotic Dirac billiard in graphene quantum dots.

Abstract: The exceptional electronic properties of graphene, with its charge carriers mimicking relativistic quantum particles and its formidable potential in various applications, have ensured a rapid growth of interest in this new material. We report on electron transport in quantum dot devices carved entirely from graphene. At large sizes (>100 nanometers), they behave as conventional single-electron transistors, exhibiting periodic Coulomb blockade peaks. For quantum dots smaller than 100 nanometers, the peaks become strongly nonperiodic, indicating a major contribution of quantum confinement. Random peak spacing and its statistics are well described by the theory of chaotic neutrino billiards. Short constrictions of only a few nanometers in width remain conductive and reveal a confinement gap of up to 0.5 electron volt, demonstrating the possibility of molecular-scale electronics based on graphene.

Graphene-based liquid crystal device.

Abstract: Graphene is only one atom thick, optically transparent, chemically inert, and an excellent conductor. These properties seem to make this material an excellent candidate for applications in various photonic devices that require conducting but transparent thin films. In this letter, we demonstrate liquid crystal devices with electrodes made of graphene that show excellent performance with a high contrast ratio. We also discuss the advantages of graphene compared to conventionally used metal oxides in terms of low resistivity, high transparency and chemical stability.

Extremely narrow plasmon resonances based on diffraction coupling of localized plasmons in arrays of metallic nanoparticles.

Abstract: We experimentally demonstrate extremely narrow plasmon resonances with half-width of just several nanometers in regular arrays of metallic nanoparticles. These resonances are observed at Rayleigh's cutoff wavelengths for Wood anomalies and based on diffraction coupling of localized plasmons. We show experimentally that reflection from an array of nanoparticles can be completely suppressed at certain wavelengths. As a result, our metal nanostructures exhibit pi-jump for the phase of the reflected light.

Plasmonic blackbody : Almost complete absorption of light in nanostructured metallic coatings

Abstract: We have experimentally demonstrated blackbodylike behavior in a thin nanostructured metallic layer shaped in the form of a composite deep diffraction grating. This behavior is recorded over a wide optical wavelength range (240--550 nm) and for a broad range of angles of light incidence $(0--75\ifmmode^\circ\else\textdegree\fi{})$ for samples with metal thickness of just 90 nm. The strong absorption at a level of 97--99% is observed for one light polarization and is attributed to excitation of localized plasmons coupled to incident light waves. We show that the studied structures exhibit anomalies which consist in disappearance of reflection for both $p$- and $s$-polarized light at corresponding ``Brewster'' angles. An effective-medium approach provides a satisfactory qualitative description of the reflection and transmission spectra in our samples and confirms their blackbody behavior.

Temperature Dependent Remanence Loops of Ion-Milled Bit Patterned Media

Abstract: Magnetic multilayered thin films with perpendicular anisotropy have been patterned into nanoscale islands by ion-milling with an oxygen-plasma patterned carbon hard mask. The islands have been studied by scanning electron microscopy (SEM) and magnetic force microscopy (MFM) to determine the switching field distribution and its origin. Larger islands exhibit coercivities of ~ 450 kA/m (5.6 kOe), but coercivity falls rapidly when island diameter falls below 40 nm. The switching field distribution becomes larger in absolute terms and as a fraction of the coercivity as island diameter falls. The origin of these effects is thought to be edge damage during ion milling and intrinsic defects (grain boundaries or dislocations) in the original magnetic thin film.

Graphene-Based Liquid Crystal Device

Abstract: Graphene is only one atom thick, optically transparent, chemically inert and an excellent conductor. These properties seem to make this material an excellent candidate for applications in various photonic devices that require conducting but transparent thin films. In this letter we demonstrate liquid crystal devices with electrodes made of graphene which show excellent performance with a high contrast ratio. We also discuss the advantages of graphene compared to conventionally-used metal oxides in terms of low resistivity, high transparency and chemical stability.