X-ray photoelectron spectroscopy characterization of amorphous and nanosized thin carbon films

Abstract

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.