Limits on Charge Carrier Mobility in Suspended Graphene due to Flexural Phonons

The temperature dependence of the mobility in suspended graphene samples is investigated. In clean samples, flexural phonons become the leading scattering mechanism at temperature $T\gtrsim 10\mathrm{K}$, and the resistivity increases quadratically with $T$. Flexural phonons limit the intrinsic mobility down to a few ${\mathrm{m}}^2/\mathrm{V}\mathrm{s}$ at room $T$. Their effect can be eliminated by applying strain or placing graphene on a substrate.

Figure 1

(a) Two phonon diagram which describes electron scattering. (b) Kinematics of the process. The circle denotes the Fermi surface.

Figure 2

(a) Contribution to the resistivity from flexural phonons (blue full line) and from in-plane phonons (red dashed line). (b) Resistivity for different strain. The in-plane contribution (broken red line) shows a crossover from a low to a high—$T$ regime. In both cases, the electronic concentration is $n={10}^{12}{\mathrm{cm}}^{-2}$.

Figure 3

(a) Electron transport in suspended graphene. Graphene resistivity $\varrho =R(w/l)$ as a function of gate-induced concentration $n$ for $T=5$, 10, 25, 50, 100, 150, and 200 K. (b) Examples of $\mu (T)$. The $T$ range was limited by broadening of the peak beyond the accessible range of $n$. The inset shows a scanning electron micrograph of one of our suspended device. The darker nearly vertical stripe is graphene suspended below Au contacts. The scale is given by graphene width of about $1\mu \mathrm{m}$ for this particular device.