Deposition of graphene by sublimation of pyrolytic carbon

摘要

We report on the study of deposition of carbon films on different substrates: (001) Si, (001) Si covered with 300 nm SiO_2(Si/SiO_2) film as well as on (001) Si covered with SiO_2 and diamond-like carbon layers (DLC) carried out by sublimation of pyrolytic carbon layers. It is established by Raman as well as by X-ray photoelectron spectroscopy (XPS) that the layers deposited on Si as well as on Si/SiO_2 substrates consist of amorphous sp2-bonded carbon (α-C) and the longer deposition time leads to formation of micro-sized α-C islands. The Raman studies of the films deposited on the SiO_2 covered areas in the third type substrates have requisites of defected graphene (presence of clear D and weak broadening of the 2D band while the intensity ratio of 2D to G and D bands remains high: more than 2.5 and 3.1, respectively) and the films are predominantly single-layered. These films are determined as "polygraphene" (mainly single-layered graphene film consisting of mutually misoriented areas). The films deposited on the DLC paths in the third type of substrates most probably consist of few layers of mixed few-layered polygraphene and (sp~2C)- and (sp~3C)- H phases. The thorough XPS study indirectly confirms the above conclusions. The formation of polygraphene and mixed phases is explained with nucleation of many stable carbon aggregates which, once formed, are not sufficiently mobile to mutually re-orientate until forming defect-free graphene.