# Characterization of Graphene Carbon Produced by Pulsed Laser Ablation of Sacrificial Carbon Tapes
## 3 Results  
The diffraction pattern of the target material (Figure 2) demonstrates the appearance of broadened 002 (20 = 25\({}^{\circ}\)) and 10 (20 = 43\({}^{\circ}\)) turbostatic carbon peaks, and is similar to the carbon black XRD pattern [31]. From peak position and FWHM evaluation, the crystallite sizes in the [001] and [100] directions were 1.6 nm and 3.1 nm, respectively [32]. The averaged interplanar distance between the graphene layers was \(\sim\)3.7 A.  
Figure 1: Schematic of the laser ablation process. The diffraction spectra of the carbon films deposited on sapphire (Figure 2) exhibit less intense, broad 002 peaks, slightly shifted to lower angles in comparison with the corresponding target peak. The peak shift is due to the increase in interlayer spacing, by about 0.1 A. Additionally, a weakly resolved bump at 2\(\theta\)\(\approx\) 43\({}^{\circ}\) can be observed for the GLC/sapphire-2 sample (inset in Figure 2), which lies in the region of 10 reflections. The resulting diffractograms are characteristic of a turbostatic structure [31; 33; 34], and are similar to the reduced graphene oxide XRD pattern [35]. Figure 3a shows the survey XPS spectrum of the TCS-CARB-1 target material. This spectrum only features carbon and oxygen peaks. Figure 3b demonstrates the high-resolution C1s core-level XPS spectrum of the target. This spectrum was deconvoluted into five different chemically shifted components. The XPS data are shown in Table 1. Peak A (284.3 eV) is related to sp\({}^{2}\)-bonded carbon atoms with perfect graphene lattices (C=C bond) [36]. We attribute peak B (285.6 eV) to the carbon being partially sp\({}^{3}\) bonded [37], and to the presence of sp\({}^{3}\)-hybridized C-H bonds [32]. The peaks C, D and E correspond to the following oxygen-containing groups: epoxide (C-O-C) [35; 38; 39] and hydroxyl groups (-287 eV), C=O carbonyl groups (288.5 eV) [40; 41], and carboxyl O=C-OH groups (289.9 eV) [42]. Figure 3: XPS spectra of the target material and carbon film, deposited on silver. Survey (**a**,**c**) and high-resolution C1s spectra (**b**,**d**). Figure 2: XRD patterns of the target material and carbon films on sapphire substrate. Figure 3c demonstrates the survey XPS spectrum of the GLC film deposited on silver substrate. The spectrum features carbon, oxygen and silver peaks. The high-resolution C1s XPS spectrum of the nanocarbon film is presented in Figure 3d. The C1s spectrum features similar A, B, C and D peaks, with modified positions and intensities. Peak A (284.4 eV), with increased intensity, is still related to sp\({}^{2}\)-bonded graphenic carbon. In contrast, peak B (285.3 eV) shifted to lower energy, and its intensity decreased significantly compared to peak A. The latter can be explained by a significant decrease in the content of organic vehicle, and, accordingly, in the content of C-H bonds. The ratio of the integral intensities of A/B can be used to estimate the sp\({}^{2}\)/sp\({}^{3}\) fraction in the material (Table 1) [43]. Compared to the target material, peak C is shifted towards lower binding energies and has a much lower intensity, which may indicate the loss of oxygen from epoxy and hydroxyl groups as a result of ablation, and a decrease in the fraction of epoxy groups relative to hydroxyl groups. The component D only slightly decreased in intensity. It should be noted that the F component appears in the spectrum of the film, which is interpreted as a \(\pi\)\(\rightarrow\)\(\pi^{\ast}\) shake-up satellite [44]. The latter indicates an increase in the fraction of sp\({}^{2}\) carbon. Figure 4a shows the Raman spectra of the two carbon films, deposited on sapphire at different laser fluxes. The spectra demonstrate three intense bands, namely, G (\(\sim\)1586 cm\({}^{-1}\)), D (\(\sim\)1357 cm\({}^{-1}\)), and 2D (\(\sim\)2700 cm\({}^{-1}\)), which are characteristic of all graphenic carbons, including amorphous carbon [45].