Figure 1

STM images of (a) SLG and (b) H-SLG. Tunneling parameters: $V$ $=$ −0.60 V, $I$ $=$ 0.1 nA. [Inset of (b)] Fourier transform of STM image of H-SLG. (c) C 1$s$ XPS spectrum ($h{\upsilon }_{\mathrm{in}}$ $=$ 400 eV) of SLG (top) and 0.42 ML H-SLG (bottom). (d) Sketches of pinning of carbon atoms to Pt surface atoms after hydrogenation at the bright parts of the moiré [(top) SLG on Pt(111); (bottom) H-SLG on Pt(111)]. (e) Pt 4$f_{7/2}$ XPS spectra ($h{\upsilon }_{\mathrm{in}}$ $=$ 165 eV) of SLG (top) and H-SLG (bottom). Spectra were deconvoluted using Gaussian-broadened Doniach-Šunjić functions. Assignments of C–Pt, C-$s{p}^2$, C–H, and defect components are made based on Pt 4$f_{7/2}$ XPS, XAS (see Fig. 2), and TPD measurements.Reuse & Permissions

Figure 2

XES and XAS spectra of SLG and H-SLG showing σ and π states, before and after hydrogenation. The C 1$s$ binding energy position of the $s{p}^2$ hybridized state provides the Fermi level of the systems. Energy values are absolute relative to the Fermi level (dotted line). The normal emission XES spectra of SLG and H-SLG were normalized to the peak heights. The π component of the $o$-DOS was extracted by subtraction of the half-normal emission spectra from grazing emission spectra after area normalization. Indicated with bars are the energy positions of certain high-symmetry critical points for pure graphene. The critical points indicated are related to π (blue) and σ symmetry (green). XES spectra were recorded with incident photon energy, $h{\upsilon }_{\mathrm{in}}$ $=$ 320 eV. Note that normalization between the XAS and the XES spectra are arbitrary.Reuse & Permissions

Figure 3

Resonant π symmetry XES and XAS spectra of SLG and H-SLG. The π symmetry XAS spectra were normalized to the intensity maximum of the ${\pi }^{*}$ resonance peak. Difference XES spectra from SLG and H-SLG were obtained by subtracting 2$p_x$+2$p_y$ components (σ, normal emission) from 2$p_x$+2$p_y$+2$p_z$ components (σ+π, grazing emission). Elastic emission peaks were cut for clarity. XES spectra were recorded with $h{\upsilon }_{\mathrm{in}}$ $=$ 287.5 eV (excitation energy represented by blue arrow in the corresponding XAS spectra).Reuse & Permissions

Figure 4

DFT-optimized structure for 0.5 ML H-SLG on Pt(111) showing (a) side view and (b) top view. Carbon atoms are green (carbon atoms bonded to hydrogen) and blue (carbon atoms bonded to Pt substrate). Hydrogen atoms are orange; Pt atoms are grey. C–Pt bonds (blue) are 2.1 Å in length.Reuse & Permissions

Figure 5

σ (a) and π (b) symmetry DOS calculated for geometry-optimized structure SLG on Pt(111) and 0.5 ML H-SLG on Pt(111). Individual contributions of carbon atoms bonded to hydrogen and Pt for H-SLG are also indicated. The total DOS for H-SLG is slightly offset to display the significance of contribution of carbon atoms bonded to Pt.Reuse & Permissions