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| VOLUME 88 | ISSUE 5 |
PAGE 370
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| Effect of Coulomb scattering on graphene conductivity |
V. Vyurkov, V. Ryzhii+
Institute of Physics and Technology RAS, 117218 Moscow, Russia
+University of Aizu, Aizu-Wakamatsu 965-8580, and Japan Science and Technology Agency, CREST, 107-0075 Tokyo, Japan
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PACS: 73.63.-b, 81.05.Uw
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Abstract
The effect of Coulomb scattering on graphene conductivity in field
effect transistor structures is discussed. Inter-particle scattering
(electron-electron, hole-hole, and electron-hole) and scattering on charged
defects are taken into account in a wide range of gate voltages.
It is shown that an intrinsic conductivity of graphene (purely
ambipolar system where both electron and hole densities exactly
coincide) is defined by strong electron-hole scattering. It has a
universal value independent of temperature. We give an explicit
derivation based on scaling theory. When there is even a small
discrepancy in electron and hole densities caused by applied gate
voltage the conductivity is determined by both strong electron-hole
scattering and weak external scattering: on defects or phonons. We suggest
that a density of charged defects (occupancy of defects) depends on Fermi
energy to explain a sub-linear dependence of conductivity on a
fairly high gate voltage observed in experiments. We also eliminate
contradictions between experimental data obtained in deposited and suspended
graphene structures regarding graphene conductivity.
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