Interface atomic structure and interactions at graphene/insulator heterostructure

グラフェン/絶縁体ヘテロ構造における原子構造及び界面相互作用

圓谷 志郎; Sorokin, P. B.*; Avramov, P.*; 大伴 真名歩; 松本 吉弘; Antipina, L. Y.*; 平尾 法恵; 下山 巖   ; 楢本 洋*; 馬場 祐治  ; 境 誠司

Entani, Shiro; Sorokin, P. B.*; Avramov, P.*; Otomo, Manabu; Matsumoto, Yoshihiro; Antipina, L. Y.*; Hirao, Norie; Shimoyama, Iwao; Naramoto, Hiroshi*; Baba, Yuji; Sakai, Seiji

Recently, graphene has proved interesting for nanoelectronics and spintronics. Direct growth of graphene on insulator substrates is currently one of the most important subjects for development graphene-based devices. In the present study, single-layer graphene was directly grown on an atomically flat a-AlO(0001) substrate and its atomic structure was investigated by element-specific normal incident X-ray standing wave spectroscopy. It is revealed that graphene is adjacent to the oxygen atoms which constitute the topmost layer of a-AlO(0001) at the interface. The vertical distance between graphene and a-AlO(0001) is determined to be 0.26 nm, suggesting strong interfacial interactions rather than van der Waals interactions. Raman and X-ray photoelectron spectroscopy indicate heavy hole doping in graphene as well as non-chemical interactions at the interface. Theoretical calculations reveal that these situations are resulted from the electrostatic interaction between the graphene pi system and unsaturated electrons of the topmost oxygen layer.