BEOL-compatible synthesis of multi-layer graphene by carbon ion implantation on cobalt thin films

We present a study on the synthesis of multi-layer graphene using carbon ion implantation on thin cobalt (Co) films. Carbon ions were bombarded at 20 keV and doses of 4 × 10¹⁵ cm⁻² and 8 × 10¹⁵ cm⁻² onto the surface of a Co/SiO₂/Si substrate. This process was followed by heat treatment (500–900 °C) to form graphene on Co film. The effects of the heating conditions were systematically investigated by micro-Raman spectroscopy and transmission electron microscopy. The result proved that multi-layer graphene with high coverage, even at moderate temperature and with a relatively short period of time, was synthesized on the cobalt film when the amount of carbon source inside the cobalt was sufficient. A phase transition of Co film from hcp to fcc turned out to be deeply related to graphene formation at moderate temperatures. The phase transition induces synthesis of graphene on cobalt film at 450–500 °C, although it causes some defects in the graphene. Our results indicate that moderate temperature synthesis of graphene on Co film using carbon ion implantation provides a facile and direct route for integrating graphene with Si microelectronics.