Infrared spectroscopic study of carrier scattering in gated CVD graphene

We measured Drude absorption of gated CVD graphene using far-infrared transmission spectroscopy and determined the carrier scattering rate ($\ensuremath{\gamma}$) as a function of the varied carrier density ($n$). The $n$-dependent $\ensuremath{\gamma}(n)$ was obtained for a series of conditions systematically changed as (10 K, vacuum) $\ensuremath{\rightarrow}$ (300 K, vacuum) $\ensuremath{\rightarrow}$ (300 K, ambient pressure), which reveals that (1) at low-T, charged impurity ($=A/\sqrt{n}$) and short-range defect ($=B\sqrt{n}$) are the major scattering sources which constitute the total scattering $\ensuremath{\gamma}=A/\sqrt{n}+B\sqrt{n}$, (2) among various kinds of phonons populated at room-$T$, surface polar phonon of the ${\mathrm{SiO}}₂$ substrate is the dominantly scattering source, and (3) in air, the gas molecules adsorbed on graphene play a dual role in carrier scattering as charged impurity center and resonant scattering center. We present the absolute scattering strengths of those individual scattering sources, which provides the complete map of scattering mechanism of CVD graphene. This scattering map allows us to find out practical measures to suppress the individual scatterings, the mobility gains accompanied by them, and finally the ultimate attainable carrier mobility for CVD graphene.