Crystallization of diamond-like carbon to graphene under low energy ion beam modification

Low-energy ion beam modification was proposed to create graphene on the top of the insulated diamond-like carbon films. In such low-temperature fabrication process the surface of the amorphous carbon could crystallize to graphene as a result of point defect creation and enhanced diffusion caused by the ion bombardment. In the experiment 130 eV argon ion irradiation was used. After the modification the resistivity of the sample surface drops. Raman spectra of the samples measured at 633 nm showed partial crystallization and were similar to the spectra of defected graphene. This result is very encouraging and we hope that by improving this technology it will be possible to fabricate defect-free graphene, which can be used in electronics without transfer to other substrates Introduction: Graphene have been the subject of research in the recent years because of its unique electrical, optical and mechanical properties. These properties make them an ideal material for many applications in electronics. Various methods were demonstrated for deposition of large-area graphene films. In the most successfully chemical vapor deposition (CVD) methods such films are deposited on a metal catalytic layer (Ni, Co) or on Cu (using low solubility of carbon in Cu) [1, 2]. However, in the electronics usually graphene sheets on insulating substrates are needed. Therefore the graphene thin films deposited on metals are transferred to insulating substrates, which is a difficult step. Additionally the properties of transferred graphene are deteriorated from large numbers of traps and phonon scattering in typical substrates used like SiO2. During the writing this paper a publication arise [3], where graphen was transferred to diamond-like carbon substrates. Graphene transistors fabricated from graphen on diamond-like carbon have better properties because of a less impurity and phonon scattering. The disadvantages of graphene transfer, however, still remained. Here, we present an alternative low temperature method of fabrication of graphene layers on the top of insulated diamond-like carbon films by low energy ion beam irradiation. Generally, ion bombardment causes structural damage in a crystalline material. However, in the ion beam irradiation of amorphous material, ion beam induced epitaxial crystallization of amorphous layers is possible. The mechanism for such crystallization process involves point defect creation and enhanced diffusion caused by ion bombardment. One should mention that there is a technology for fabrication of graphen without its transfer. In this technology graphene is grown on the semi-insulation surface of SiC by high temperature thermal decomposition of silicon carbide [4]. However, this process requires temperatures over 1000oC and is not compatible with the current semiconductor technology. Calculation of the necessarily ion beam parameters: Different ions can be used to modify diamond-like carbon films. Three types of ions were analyzed as possible candidates for low energy ion beam modification of amorphous carbon films. The first two are carbon and hydrogen ions, which are inherent to our a-C:H films and we do not  e-mail: [email protected] 1