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Carbon exists in the form of many allotropes: zero-dimensional sp2 fullerenes, the two- dimensional (2D) sp2 honeycomb lattice of graphene (parent to graphite and carbon nanotubes), or three-dimensional (3D) sp3 crystals - diamond and lonsdaleite. Carbon can also exist in the form of carbine, a one dimensional (1D) infinite chain of sp1-hybridized carbon atoms. Each of them has notably different electronic and mechanical properties. Accordingly, it is highly important to correctly identify the hybridization state of carbon for the industrial application of these materials. It is well known that the phase ratio of sp2 and sp3 hybridized carbon is distinguishable by X-ray Photoelectron Spectroscopy (XPS) and especially by analysis of C1s lines. Here we report on a thorough XPS study of thin carbon films deposited by pulsed laser deposition (PLD). The studied films consist of a mix of carbon phases deposited on SiO2/(001)Si substrates. The obtained XPS results allows the optimization of PLD process parameters in order to synthesize single to few layered defected graphene/ graphene-like films.

The fabrication of nano-crystalline carbon films was implemented by the application of pulsed laser deposition (PLD) technology. The experiments were performed in a standard on-axis laser ablation (LA) configuration. The third harmonic of a Nd:YAG laser was used for ablation of a microcrystalline graphite target. All experiments were performed in vacuum at a pressure of 1×10-3 Pa for different deposition times. (001) Oriented silicon (Si) covered by either 350 or 450 nm silica (SiO2) layer was used as a substrate. The films have a thickness between 4 and 40 nm and are characterized by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, atomic force microscopy (AFM) and ellipsometry measurements. We established deposition of nano-sized graphene-like films on top of predominantly amorphous carbon films with a thickness of 1- 2 nm. The measured the (n and k) and determined the values for the forbidden gap of the films which are between 0.01 eV and about 1 eV with reference to the sp3 hybridized carbon content of the film.

The initial stages of deposition of graphene-like thin films have been studied by X-ray photoelectron spectroscopy, scanning electron microscopy, Raman spectroscopy and ellipsometry. The deposition process has been performed by sublimation of amorphous carbon on 330 nm SiO2/ (001) Si substrates with surface area of 15× 15 mm2. The sublimation process was carried out in a quartz tube having an internal diameter of 25 mm at a temperature of 1050°C in which samples were placed in an argon flow of about 1 cm3/s for 3 to 15 minutes. As a source of amorphous carbon, modified carbon blacks SPHERON 5000 were used. We established that an amorphous carbon film with thickness up to 3-6 nm is always deposited on the SiO2 after 3-5 min deposition and the deposition of a few-layered defected graphene as well as nano-sized graphite occurs after 5-6 min on the surface of substrate. Further on, after 8-10min deposition a non-continuous carbon film is formed and after 12-13 min the substrate is covered by a smooth and continuous carbon film. The film has extremely low resistivity (ρ= 2.8 × 10−6Ω.m) and consists of predominantly sp2 hybridized carbon with a Raman spectrum similar to those of nano-sized graphene.The initial stages of deposition of graphene-like thin films have been studied by X-ray photoelectron spectroscopy, scanning electron microscopy, Raman spectroscopy and ellipsometry. The deposition process has been performed by sublimation of amorphous carbon on 330 nm SiO2/ (001) Si substrates with surface area of 15× 15 mm2. The sublimation process was carried out in a quartz tube having an internal diameter of 25 mm at a temperature of 1050°C in which samples were placed in an argon flow of about 1 cm3/s for 3 to 15 minutes. As a source of amorphous carbon, modified carbon blacks SPHERON 5000 were used. We established that an amorphous carbon film with thickness up to 3-6 nm is always deposited on the SiO2 after 3-5 min deposition and the deposition of a few-layered defected graphene as well as nano-sized graphite occurs after 5-6 min on the surface of substrate. Further on, after 8-10min deposition a non-continuous carbon film is formed and after 12-13 min the substrate is covered by a smooth and cont...

We synthesized undoped as well as up to 6 at.% nitrogen (N) doped thin amorphous carbon (α-C) films by plasma- enhanced chemical vapor deposition (PECVD) method. The source of carbon/carbon containing radicals was benzene (C6H6) in Ar gas- mixture. The obtained thin films were studied by optical microscopy, X-ray powder diffraction, UV-VIS- NIR Spectral Ellipsometry, IR and Raman spectroscopic studies as well as by X-ray photoelectron spectroscopies (XPS). We established by XPS that the deposited layers consist of a mix of sp2 and sp3 hybridized carbon. The films are amorphous as it was shown by the measured XRD patterns. The ellipsometric measurements enabled calculation of transition energies and the complex results showed that films with thickness of 15- 120 nm and different properties can be obtained by this technique.