Direct growth of graphene on insulators is expected to yield significant improvements in performance of graphene-based electronic and spintronic devices. In this study, we successfully reveal the atomic arrangement an...Direct growth of graphene on insulators is expected to yield significant improvements in performance of graphene-based electronic and spintronic devices. In this study, we successfully reveal the atomic arrangement and electronic properties of a coherent heterostructure of single-layer graphene and α-Al2O3（0001）. The analysis of the atomic arrangement of single-layer graphene on α-Al2O3（0001） revealed an apparentcontradiction. The in-plane analysis shows that single-layer graphene grows not in a single-crystalline epitaxial manner, but rather in polycrystalline form, with two strongly pronounced preferred orientations. This suggests relatively weak interfacial interactions are operative. However, we demonstrate that unusually strong physical interactions between graphene and α-Al2O3（0001） exist, as evidenced by the small separation between the graphene and the α-Al2O3（0001） surface. The interfacial interaction is shown to be dominated by the electrostatic forces involved in the graphene n-system and the unsaturated electrons of the topmost O layer of α-Al2O3（0001）, rather than the van der Waals interactions. Such features causes graphene hole doping and enable the graphene to slide on the α-Al2O3（0001） surface with only a small energy barrier despite the strong interfacial interactions.展开更多
基金We are grateful to the ＇Chebishev＇ and ＇Lomonosov＇ supercomputers of Moscow State University for providing the chance of using a cluster computer for quantum-chemical calculations. S.E. thanks Prof. H. Kondo （Keio University） and Prof. T. Shimada （Hirosaki University） for NIXSW measurements. This work was partly supported by Grants-in-Aid for Young Scientists B （Grant No. 22760033） from the Japan Society for the Promotion of Science. The present work has been performed under the approval of the Photon Factory Program Advisory Committee （PF PAC Nos. 2010G660 and 2012G741）. P.V.A., P.B.S. and L.Y.A. acknowledge the support from the Russian Science Foundation （project No. 14-13-00139）.
文摘Direct growth of graphene on insulators is expected to yield significant improvements in performance of graphene-based electronic and spintronic devices. In this study, we successfully reveal the atomic arrangement and electronic properties of a coherent heterostructure of single-layer graphene and α-Al2O3（0001）. The analysis of the atomic arrangement of single-layer graphene on α-Al2O3（0001） revealed an apparentcontradiction. The in-plane analysis shows that single-layer graphene grows not in a single-crystalline epitaxial manner, but rather in polycrystalline form, with two strongly pronounced preferred orientations. This suggests relatively weak interfacial interactions are operative. However, we demonstrate that unusually strong physical interactions between graphene and α-Al2O3（0001） exist, as evidenced by the small separation between the graphene and the α-Al2O3（0001） surface. The interfacial interaction is shown to be dominated by the electrostatic forces involved in the graphene n-system and the unsaturated electrons of the topmost O layer of α-Al2O3（0001）, rather than the van der Waals interactions. Such features causes graphene hole doping and enable the graphene to slide on the α-Al2O3（0001） surface with only a small energy barrier despite the strong interfacial interactions.
