Graphite in the bilayer regime: In-plane transport

An interplay between the increase in the number of carriers and the decrease in the scattering time is expected to result in a saturation of the in-plane resistivity, ${\rho }_{ab}$, in graphite above room temperature. Contrary to this expectation, we observe a pronounced increase in ${\rho }_{ab}$ in the interval between 300 and 900 K. We provide a theory of this effect based on intervalley scattering of charge carriers by high-frequency, graphenelike optical phonons.

Figure 1

(Color online). Measured temperature dependence of the in-plane resistivity of HOPG for warming (filled squares) and cooling (blank squares) temperature sweeps. Dashed: theoretical prediction for ${\rho }_{ab}\left(T\right)$ in the model containing scattering at impurities and soft phonons. Solid: fit using the model containing scattering at impurities, soft phonons, and intervalley scattering at hard in-plane optical phonons [Eq. (17)]. Inset: overlap of the data for two different samples. The vertical scales were shifted for clarity.

Figure 2

(Color online). (a) XPS spectra before and after annealing. (b) AES spectra before and after annealing. Insets: magnified carbon peaks.