Electron and optical phonon temperatures in electrically biased graphene.

We examine the intrinsic energy dissipation steps in electrically biased graphene channels. By combining in-situ measurements of the spontaneous optical emission with a Raman spectroscopy study of the graphene sample under conditions of current flow, we obtain independent information on the energy distribution of the electrons and phonons. The electrons and holes contributing to light emission are found to obey a thermal distribution, with temperatures in excess of 1500 K in the regime of current saturation. The zone-center optical phonons are also highly excited and are found to be in equilibrium with the electrons. For a given optical phonon temperature, the anharmonic downshift of the Raman G mode is smaller than expected under equilibrium conditions, suggesting that the electrons and high-energy optical phonons are not fully equilibrated with all of the phonon modes.

[1]  C. Dimitrakopoulos,et al.  100-GHz Transistors from Wafer-Scale Epitaxial Graphene , 2010, Science.

[2]  F. Xia,et al.  Graphene field-effect transistors with high on/off current ratio and large transport band gap at room temperature. , 2010, Nano letters.

[3]  J. Smet,et al.  Hot phonons in an electrically biased graphene constriction. , 2010, Nano letters.

[4]  B. Park,et al.  Interference effect on Raman spectrum of graphene on SiO 2 / Si , 2009, 0908.4322.

[5]  E. al.,et al.  Time-resolved Raman spectroscopy of optical phonons in graphite: Phonon anharmonic coupling and anomalous stiffening , 2009, 0908.3036.

[6]  D. Basko,et al.  Electron-electron interactions and doping dependence of the two-phonon Raman intensity in graphene , 2009, 0906.0975.

[7]  Joel Moser,et al.  Transport properties of graphene in the high-current limit. , 2009, Physical review letters.

[8]  Phaedon Avouris,et al.  Phonon populations and electrical power dissipation in carbon nanotube transistors. , 2009, Nature nanotechnology.

[9]  P. Avouris,et al.  Energy dissipation in graphene field-effect transistors. , 2009, Nano letters.

[10]  K. Shepard,et al.  Current saturation in zero-bandgap, top-gated graphene field-effect transistors. , 2008, Nature nanotechnology.

[11]  J. Misewich,et al.  Measurement of the optical conductivity of graphene. , 2008, Physical review letters.

[12]  N. Peres,et al.  Fine Structure Constant Defines Visual Transparency of Graphene , 2008, Science.

[13]  P. Kim,et al.  Temperature-dependent transport in suspended graphene. , 2008, Physical review letters.

[14]  R. Krupke,et al.  Raman spectroscopic evidence for hot-phonon generation in electrically biased carbon nanotubes. , 2008, Physical review letters.

[15]  S. Xiao,et al.  Intrinsic and extrinsic performance limits of graphene devices on SiO2. , 2007, Nature nanotechnology.

[16]  Nicola Marzari,et al.  Phonon anharmonicities in graphite and graphene. , 2007, Physical review letters.

[17]  C. N. Lau,et al.  Variable temperature Raman microscopy as a nanometrology tool for graphene layers and graphene-based devices , 2007 .

[18]  Andre K. Geim,et al.  The rise of graphene. , 2007, Nature materials.

[19]  Andre K. Geim,et al.  Raman spectrum of graphene and graphene layers. , 2006, Physical review letters.

[20]  M. Lazzeri,et al.  Coupled dynamics of electrons and phonons in metallic nanotubes: Current saturation from hot-phonon generation , 2006, cond-mat/0603046.

[21]  H. Dai,et al.  Negative differential conductance and hot phonons in suspended nanotube molecular wires. , 2005, Physical review letters.

[22]  J. Maultzsch,et al.  Double-resonant Raman scattering in graphite: Interference effects, selection rules, and phonon dispersion , 2004 .

[23]  H. Kuzmany.  Solid-state spectroscopy , 1998 .