Improvement of multilayer graphene crystallinity by solid-phase precipitation with current stress application during annealing

To improve the crystallinity of multilayer graphene (MLG) films by solid-phase precipitation, a new method by which current stress is introduced during annealing of a carbon-doped cobalt (Co-C) layer using cobalt (Co) as the catalyst has been investigated. The effects of current stress on the formation and crystallinity of MLG films were investigated by comparing the characteristics of the films annealed at the same temperature with and without current by taking into account the temperature rise due to Joule heating. The characteristics obtained by Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) measurements revealed that the MLG films produced were crystalline in nature and their crystallinity increased with applied current stress at the same temperature. From SEM observations, beside Joule heating, enhancement of Co grain size by agglomeration induced by current stress may be the potential reason for the improvement of the crystallinity of MLG films. We have also improved the uniformity of MLG films by depositing an additional copper (Cu) capping layer over the Co-C layer. Current stress application can lead to low-temperature fabrication of MLG with higher crystallinity by solid-phase precipitation.