Chemical vapor deposition of graphene on refractory metals: The attempt of growth at much higher temperature

Abstract

Large area graphene is usually grown by chemical vapor deposition on Cu or Ni catalysts at ∼1000 °C. For most materials, high temperature leads to high quality. However, graphene growth at even higher temperatures is rarely reported. Therefore, here we systematically investigate the graphene deposition on refractory metals i.e. metals with extremely high melting points. The growth parameters and material characterizations are given in detail. On Ta which readily forms carbides during the carbon deposition, the growth mode is monolayer due to the chemical absorption of excess carbon in the bulk metal. On Re, there is no carbide formed (except in extreme conditions), which greatly simplifies the scenario. Because of the relatively high carbon solubility in Re, the growth temperature has to be limited in order not to drift into the dominantly multilayer graphene regime caused by the carbon segregation. Graphene with reasonable quality has been achieved, although not as good as expected. For example, on Ta, the residual bonds between the graphene and substrate deteriorate the graphene crystalline quality. Despite the difficulties in refractory metal etching, the transfer technique of the graphene is also explored. This research contributes to the fundamental understanding of the graphene growth theory and technology on refractory metals.