# Characterization of Graphene Carbon Produced by Pulsed Laser Ablation of Sacrificial Carbon Tapes
## 2 Materials and Methods  
As a target material for laser ablation, we used the commercial carbon tape TCS-CARB-1 from the manufacturer C12 Advanced Technologies [29], which is typically composed of micro/nanocrystalline graphite-like carbon of high purity, dispersed in an organic vehicle.  
Carbon films were prepared by PLD using 1064 nm IR Q-switched Nd:YAG laser with 40 ns pulse width. The use of 1064 nm wavelength was due to the fact that graphenic carbon with a significant oxygen content (including GO) demonstrates high absorptivity in the near- and mid-IR regions [16], so the irradiation of 1064 nm laser pulse should generate instantaneous and strong localized heating and burst apart the oxygen functional groups. On the other hand, the photon energy of 1064 nm irradiation is not sufficient for C=C bond photoionization, which should reduce the number of structural defects in the sp\({}^{2}\) network in comparison with shorter wavelengths. We used nanosecond laser pulses in order to keep electronic subsystem in thermal equilibrium with lattice, which results in more uniform heating [30]. The deposition was performed in specially designed inert chamber (Figure 1) on a He background at room temperature onto sapphire and silver substrates. Prior to the deposition, the substrates were ultrasonically cleaned in deionized water and isopropyl alcohol. The use of an inert gas was due to the need to remove the decomposition products of the organic vehicle from the deposition chamber. For this purpose, He was continuously pumped through the chamber at atmospheric pressure. Two different laser energies, namely, 6 J/cm\({}^{2}\) (GLC/sapphire-1) and 4 J/cm\({}^{2}\) (GLC/sapphire-2), were used for deposition on sapphire substrates. The laser fluences were chosen based on preliminary experiments and previous works [3, 18, 27]. The samples on conductive silver substrate (laser fluence--4 J/cm\({}^{2}\)) were used for the XPS measurements. During deposition, the substrate-target distance was fixed at 25 mm for all the samples. The laser beam, which focused on the spot of \(\sim\)100 \(\upmu\)m, using 20 cm focal length F-Theta lens, was continuously moved over the target surface at a speed of 3 mm/s using a scanning module with two galvanometers. The scanning speed was selected based on the thickness of the carbon tape. The laser spot was moved over the target in the spiral trajectory. The total ablated area on the carbon target was about 5 mm in diameter. We used a high pulse repetition rate of 500 Hz and a deposition time of 10 s for all samples.  
The XRD measurements were carried out using Cu \(K\alpha\) radiation (DRON-3 double-crystal diffractometer) in Bragg-Brentano focusing geometry. XPS was used to study the features of the chemical bonds on the surface layers of carbon films. XPS spectra were obtained with ESCALAB 250 spectrometer using monochromated Al \(K\alpha\) radiation (1486.6 eV). The energy resolution measured on the Ag3d\({}_{5/2}\) line was 0.6 eV. Raman spectra were measured at room temperature with a Renishaw inVia Raman microspectrometer equipped with a 2.41 eV excitation energy Ar\({}^{+}\) laser (514.5 nm). The spot size was \(\sim\)4 \(\upmu\)m focused with a 50\(\times\) objective. The laser power was kept lower than 4 mW to avoid laser-induced heating and damage to the samples. The spectra were collected from the different points in both the central and edge regions of the films. No fundamental differences were observed between the spectra in each of the sample regions. The edge regions, however, demonstrated a significant photoluminescence background. For the same reason, it was not possible to obtain the Raman spectrum of the target carbon tape.