<i>C</i>-Axis Resistivity of Graphite in Connection with Stacking Faults

Ono, Shûsuke

doi:10.1143/jpsj.40.498

Cited by 50 publications

(10 citation statements)

References 5 publications

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“…Here, we demonstrate an electric field-effect in crystallites of highly oriented pyrolytic graphite (HOPG), by utilizing the large anisotropy in charge transport arising due to their quasi-two-dimensional (quasi-2D) electronic structure. 12,13 We achieve this by steering the charge transport through the uppermost layers of the crystallite and by deploying a polymer electrolyte gate. The observation of a field-effect in graphite complements the well-documented behaviour of field-effect devices comprised of few-layer graphene.…”

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confidence: 99%

Electric field effect in graphite crystallites

Sagar

Balasubramanian

Burghard

et al. 2012

Applied Physics Letters

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Graphite is a highly anisotropic crystal with a quasi-two-dimensional electronic structure exhibiting high intrinsic charge carrier mobility. Here, we investigate the effect of an electric field on the resistance of individual graphite crystallites with a thickness on the order of 40 nm. Ambipolar field-effect behavior was achieved with the aid of a polymer electrolyte gate. By optimizing the device geometry, devices with an on/off current ratio of up to 4 and carrier mobilities of around 100 cm2/Vs could be attained directly on the crystallites.

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confidence: 99%

Electric field effect in graphite crystallites

Sagar

Balasubramanian

Burghard

et al. 2012

Applied Physics Letters

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“…After optical excitation the energy absorbed by the electrons is redistributed via electron-electron ͑e-e͒ scattering, electron-phonon ͑e-ph͒ scattering, and transport from the surface into the bulk. In graphite the transport of electrons out of the photoemission detection volume into the bulk is hampered due to the comparatively weak interlayer coupling and is further suppressed by frequent stacking faults in HOPG [12]. Therefore, the dynamics observed in the experiments are expected to be dominated by e-e and e-ph scattering processes with e-ph scattering becoming increasingly important closer to the Fermi level.…”

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confidence: 99%

Anisotropy of Quasiparticle Lifetimes and the Role of Disorder in Graphite from Ultrafast Time-Resolved Photoemission Spectroscopy

et al. 2001

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Femtosecond time-resolved photoemission of photoexcited electrons in highly oriented pyrolytic graphite (HOPG) provides strong evidence for anisotropies of quasiparticle (QP) lifetimes. Indicative of such anisotropies is a pronounced anomaly in the energy dependence of QP lifetimes between 1.1 and 1.5 eV -the vicinity of a saddle point in the graphite band structure. This is supported by recent ab initio calculations and a comparison with experiments on defect-enriched HOPG which reveal that disorder, e.g., defects or phonons, increases electron energy relaxation rates. DOI: 10.1103/PhysRevLett.87.267402 PACS numbers: 78.47. +p, 71.10.Ca, 79.60. -i, 81.05.Uw Studies of the ultrafast dynamics of electronic excitations in solids have challenged experiment and theory for years. Advances in ultrafast laser technology and the latest theoretical developments allow us to investigate electron dynamics in growing detail and further our understanding of fundamental scattering processes in solids at the femtosecond time scale [1,2].For an interacting 3D electron gas the standard theory of e-e scattering -Landau's theory of Fermi liquids -predicts a quadratic dependence of scattering rates on the quasiparticle (QP) energy ͑E 2 E F ͒ [3]. In a periodic potential, however, the electronic states are modified with respect to those of a free electron gas and form Bloch states which may result in different QP lifetimes at the same energy if distinct k states within the Brillouin zone are compared. Such anisotropies were indeed predicted by recent ab initio self-energy calculations for Al and Be which find strong variations of QP lifetimes for electrons in different bands [4,5]. Experimental verification of these predictions, however, remains truly challenging. Time-resolved photoemission from different copper surfaces has revealed some dependence of the measured electron dynamics on the crystallographic surface orientation, but the observed effects could not be clearly attributed to anisotropies of QP lifetimes [6]. Similar experiments on aluminum [7] have likewise not been able to identify band structure effects predicted theoretically [4].Graphite, a semimetal with layered structure, is expected to be an ideal candidate if band structure effects are to be observed experimentally. The strongly anisotropic band structure of graphite is expected to furnish electron scattering processes with similar anisotropies, leading to anomalous QP lifetimes. The special topology of the graphite band structure has indeed been used to explain apparent deviations of the electron dynamics observed on a cesiated highly oriented pyrolytic graphite (HOPG) surface [8] from the standard predictions for a 3D electron gas [9]. However, the experiments provided no evidence for anomalies that might be associated with anisotropic QP lifetimes. Furthermore, the overlap of the energy range probed experimentally in Ref. [8] and of the range of validity of the approximations used in Ref.[9] is small and calls for more detailed theoretical as well as experi...

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“…Graphene, since its rediscovery [1] in 2004, has intrigued the physics and the engineering community alike with properties such as room temperature quantum hall effect, ballistic transport and high electron mobility. Anisotropy in charge transport [3,8], coexistence of insulating and conducting behavior on the Highly Oriented Pyrolytic Graphite (HOPG) surface [2] and semi metallic behavior [4] have been the subject for extensive studies [5,6,7,11,13]. However, with all the experimental and theoretical studies being performed, contact resistance (Re), one of the primary limiting factors to device scalability, remains an issue that has hardly been addressed.…”

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confidence: 99%

Contact Resistance Studies of Metal on HOPG and Graphene Stacks

Venugopal¹,

Pirkle

Wallace

et al. 2009

AIP Conference Proceedings

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Contact resistance is one of the major factors limiting the performance of future nanoelectronic devices. Although there has been significant progress in graphene based devices since 2004 [1,11,13,19,20], there have been few studies of factors such as metal type, metal workfunction and number of layers in the graphene stack on metal/graphene contact resistance. In this work, contact resistance measurements of various metals (Cr, Ni, Pd, Pt) on Highly Oriented Pyrolytic Graphite (HOPG) and graphene (single layered and few layered) were performed. The total resistance is independent of distance indicating a contact resistance dominated system. The contact resistance is observed to be similar for a wide variety of metals although the metal workfunction varies from 4.3 eV to 5.6 eV. Similar measurements were performed for metal on single-and multi-layer graphene. The electrical results are compared with XPS measurements of thin metal on HOPG. Issues regarding the characterization and interpretation of contact resistance for metal -semimetal systems are discussed.

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C-Axis Resistivity of Graphite in Connection with Stacking Faults

Cited by 50 publications

References 5 publications

Electric field effect in graphite crystallites

Electric field effect in graphite crystallites

Anisotropy of Quasiparticle Lifetimes and the Role of Disorder in Graphite from Ultrafast Time-Resolved Photoemission Spectroscopy

Contact Resistance Studies of Metal on HOPG and Graphene Stacks

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