title: Metastable phase formation and structural evolution of epitaxial graphene grown on SiC(100) under a temperature gradient.
abstract: Multilayer epitaxial graphene was obtained from a 6H-SiC(001) substrate subjected to a temperature gradient from 1250 to 1450 °C. Scanning tunneling microscopy and x-ray diffraction were used to identify the structure and morphology of the surface, from which the formation of a metastable phase was inferred. By a comparison between microscopy and diffraction data, we report the appearance of misoriented Si-doped graphene in cold regions (1250 °C) of the substrate. This metastable phase occurs in domains where silicon sublimation is incomplete and it coexists with small domains of epitaxial graphene. At 1350 °C this phase disappears and one observes complete graphene-like layers (although misoriented), where rotational registry between the underlying epitaxial graphene and additional layers is absent. At 1450 °C the stacking among layers is established and the formation of highly oriented single crystalline graphite is complete. The stability of this Si-rich metastable phase at 1250 °C was confirmed by first-principles calculations based on the density functional theory.
authors.affiliation: Departamento de Física, Universidade Federal de Minas Gerais, CP 702, Belo Horizonte MG, 30123-970, Brazil.
authors.forename: A M B
authors.initials: AM
authors.lastname: Goncalves
authors.forename: A
authors.initials: A
authors.lastname: Malachias
authors.forename: M S
authors.initials: MS
authors.lastname: Mazzoni
authors.forename: R G
authors.initials: RG
authors.lastname: Lacerda
authors.forename: R
authors.initials: R
authors.lastname: Magalhães-Paniago