title: Epitaxial chemical vapor deposition growth of single-layer graphene over cobalt film crystallized on sapphire.
abstract: Epitaxial chemical vapor deposition (CVD) growth of uniform single-layer graphene is demonstrated over Co film crystallized on c-plane sapphire. The single crystalline Co film is realized on the sapphire substrate by optimized high-temperature sputtering and successive H(2) annealing. This crystalline Co film enables the formation of uniform single-layer graphene, while a polycrystalline Co film deposited on a SiO(2)/Si substrate gives a number of graphene flakes with various thicknesses. Moreover, an epitaxial relationship between the as-grown graphene and Co lattice is observed when synthesis occurs at 1000 °C; the direction of the hexagonal lattice of the single-layer graphene completely matches with that of the underneath Co/sapphire substrate. The orientation of graphene depends on the growth temperature and, at 900 °C, the graphene lattice is rotated at 22 ± 8° with respect to the Co lattice direction. Our work expands a possibility of synthesizing single-layer graphene over various metal catalysts. Moreover, our CVD growth gives a graphene film with predefined orientation, and thus can be applied to graphene engineering, such as cutting along a specific crystallographic direction, for future electronics applications.
authors.affiliation: Institute for Materials Chemistry and Engineering, Kyushu University, Kasuga, Fukuoka 816-8580, Japan. ago@cm.kyushu-u.ac.jp
authors.forename: Hiroki
authors.initials: H
authors.lastname: Ago
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Ito
authors.forename: Noriaki
authors.initials: N
authors.lastname: Mizuta
authors.forename: Kazuma
authors.initials: K
authors.lastname: Yoshida
authors.forename: Baoshan
authors.initials: B
authors.lastname: Hu
authors.forename: Carlo M
authors.initials: CM
authors.lastname: Orofeo
authors.forename: Masaharu
authors.initials: M
authors.lastname: Tsuji
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Ikeda
authors.forename: Seigi
authors.initials: S
authors.lastname: Mizuno