Figure 1

(Color online) Optical images of HOPG (top) and SP-1 graphite (bottom) (a) before and (b) after fluorination. (c) Bright-field TEM image of a thin HOPG fluoride sheet suspended on a grid. (d) Cross-sectional view of a folded corner of a suspended HOPG fluoride sheet. The circled area corresponds to an interlayer spacing of $6.4\text{Å}$. (e) Electron diffraction pattern of a suspended HOPG fluoride sheet. (f) Schematics of graphite fluoride. (g) EELS data showing the K-edge of carbon atoms in thin sheets of HOPG and fluoride. Inset: The K-edge of fluorine atoms in fluoride. The energy dispersion was 0.2 eV/channel, and the absolute energy loss scale was calibrated using the graphitic ${\pi }^{\ast }$ peak at 285 eV.Reuse & Permissions

Figure 2

(Color online) X-ray diffraction data of fluorinated SP-1 graphite, reduced SP-1 graphite fluoride, and SP-1 graphite. The Miller indices of the diffraction peaks are marked in the figure. The dashed line is a guide to the eye.Reuse & Permissions

Figure 3

(Color online) (a) $I\text{−}V$ characteristics of a multilayer graphene fluoride sample at selected temperatures as indicated in the figure. Inset: the optical image of the sample with the source and drain electrode marked. The graphene fluoride sheet is outlined in dotted lines. The channel is approximately $1\mu \text{m}$ from source to drain (center to center). Scale bar is $1\mu \text{m}$. (b) $I\text{−}V$ curves of the same sample near $V_{\text{sd}}=0\text{V}$. From top to bottom: $T=250$, 225, 200, 175, 160, 125, and 100 K. (c) Semi-log plot of the zero-bias differential resistance $R_0$ vs. $T^{-1/3}$ of the sample in (a). Inset: Semi-log plot of $R_0$ vs $T^{-1}$. (d) The DoS for a random configuration of fluorine atoms attached to graphene at a 50% concentration. Spin down is shown as negative values. The midgap states correspond to the $p_z$ orbitals from the carbon atoms not attached to fluorine. The DoS of CF (dashed line) is shown as a reference. The Fermi level is used as zero energy.Reuse & Permissions

Figure 4

(Color online) AFM images of the same sheet of fluorinated HOPG exfoliated on ${\text{SiO}}_2$ substrate before (left) and after (right) annealing in ${\text{H}}_2/\text{Ar}$ gas. The traces below the images correspond to the line cut across the sheet.Reuse & Permissions

Figure 5

(Color online) (a) $I\text{−}V$ characteristics of reduced graphene fluoride (solid) in contrast to CF (dashed). $I_{\text{sd}}$ of reduced CF has been reduced by a factor of 1000 to fit the scale. (b) Sheet resistance vs back gate voltage $V_g$ of a reduced CF sample showing a charge neutrality point at $V_g=24\text{V}$ with a maximum resistance of $56\text{k}\Omega$. $T=130\text{K}$. Inset: typical multiterminal reduced CF device on ${\text{SiO}}_2$/doped Si substrate. The edge of the piece is outlined in dotted line. The scale bar is $4\mu \text{m}$. (c) The sheet resistance $\rho \left(T\right)$ vs $\text{ln}\left(T\right)$ of a reduced CF sample in the temperature range of $5<T<300\text{K}$. The red dashed line is a guide to the eye. The arrow indicates 40 K. $V_g=0\text{V}$.Reuse & Permissions