Thermal transformation of carbon hybrid materials to graphene films.

We demonstrate a simple approach to grow graphene films on polycrystalline nickel (Ni) foils, in which polycrystalline carbon hybrid materials (CHMs) were used in sandwich structures (molybdenum-CHMs-Ni-molybdenum) as a carbon source for graphene, and pressure was then applied to the sandwich. The CHMs were transformed into single as well as few layer graphene by a segregation-precipitation process. The applied pressure not only increased the density of the graphene films but also reduced the vaporization of dissociated carbon molecules of the CHMs. We have explored the possibility to grow graphene films in low vacuum (5 × 10(-1) Pa) at relatively low temperatures (≤750 °C). The formation of the graphene films at 750 °C is simple and cost-effective and can be scaled up.