We report the synthesis and evidence of graphene fluoride, a two-dimensional wide bandgap semiconductor derived from graphene. Graphene fluoride exhibits hexagonal crystalline order and strongly insulating behavior with resistance exceeding $10\text{G}\Omega$ at room temperature. Electron transport in graphene fluoride is well described by variable range hopping in two dimensions due to the presence of localized states in the band gap. Graphene obtained through the reduction of graphene fluoride is highly conductive, exhibiting a resistivity of less than $100\text{k}\Omega$ at room temperature. Our approach provides a pathway to reversibly engineer the band structure and conductivity of graphene for electronic and optical applications.

The carrier mobility $\mu$ of few-layer graphene (FLG) field-effect transistors increases tenfold when the ${\mathrm{SiO}}_2$ substrate is replaced by single-crystal epitaxial $\mathrm{Pb}({\mathrm{Zr}}_{0.2}{\mathrm{Ti}}_{0.8}){\mathrm{O}}_3$ (PZT). In the electron-only regime of the FLG, $\mu$ reaches $7\times {10}^4{\mathrm{cm}}^2/\mathrm{V}\mathrm{s}$ at 300 K for $n=2.4\times {10}^{12}/{\mathrm{cm}}^2$, 70% of the intrinsic limit set by longitudinal acoustic (LA) phonons; it increases to $1.4\times {10}^5{\mathrm{cm}}^2/\mathrm{V}\mathrm{s}$ at low temperature. The temperature-dependent resistivity $\rho (T)$ reveals a clear signature of LA phonon scattering, yielding a deformation potential $D=7.8\pm 0.5\mathrm{eV}$.

We demonstrate atomic layer deposition of high-quality dielectric ${\mathrm{HfO}}_2$ films on graphene and determine the magnitude of remote oxide surface phonon scattering in dual-oxide structures. The carrier mobility in these ${\mathrm{HfO}}_2$-covered graphene samples reaches $20000{\mathrm{cm}}^2/\mathrm{V}\mathrm{s}$ at low temperature. Distinct contributions to the resistivity from surface optical phonons in the ${\mathrm{SiO}}_2$ substrate and the ${\mathrm{HfO}}_2$ overlayer are isolated. At 300 K, surface phonon modes of the ${\mathrm{HfO}}_2$ film centered at 54 meV limit the mobility to approximately $20000{\mathrm{cm}}^2/\mathrm{V}\mathrm{s}$.

Precision measurements of the effective mass $m^{*}$ in high-quality bilayer graphene using the temperature dependence of the Shubnikov–de Haas oscillations are reported. In the density range $0.7\times {10}^{12}$ $<$ $n$ $<$ $4.1\times {10}^{12}$ cm${}^{-2}$, both the hole mass $m_{\mathrm{h}}^{*}$ and the electron mass $m_{\mathrm{e}}^{*}$ increase with increasing density, demonstrating the hyperbolic nature of the bands. The hole mass $m_{\mathrm{h}}^{*}$ is approximately 20–30% larger than the electron mass $m_{\mathrm{e}}^{*}$. Tight-binding calculations provide a good description of the electron-hole asymmetry and yield an accurate measure of the interlayer hopping parameter $v_4=0.063$. Both $m_{\mathrm{h}}^{*}$ and $m_{\mathrm{e}}^{*}$ are suppressed compared with single-particle values, suggesting renormalization of the band structure of bilayer graphene induced by electron-electron interaction.

We determine the quantum scattering time ${\tau }_q$ in six graphene samples with mobility of $4400<\mu <17000{\text{cm}}^2/\text{V}\text{s}$ over a wide range of carrier density $\left(1.2<n<6\times {10}^{12}/{\text{cm}}^2\right)$. ${\tau }_q$ derived from Shubnikov–de Haas oscillation ranges $\sim 25–74\text{fs}$, corresponding to a single-particle level broadening of 4.5–13 meV. The ratio of the transport to quantum scattering time ${\tau }_t/{\tau }_q$ spans 1.5–5.1 in these samples, which can be quantitatively understood combining scattering from short-ranged centers and charged impurities located within 2 nm of the graphene sheet. Our results suggest that charges residing on the ${\text{SiO}}_2$ surface play a dominant role in limiting carrier mobility in current samples.