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論文

Contracted interlayer distance in graphene/sapphire heterostructure

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

Nano Research, 8(5), p.1535 - 1545, 2015/05

 被引用回数:19 パーセンタイル:24.62(Chemistry, Physical)

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 atomic arrangement and electronic properties of the coherent heterostructure of single-layer graphene and $$alpha$$-Al$$_{2}$$O$$_{3}$$(0001). In the atomic arrangement analysis of single-layer graphene on $$alpha$$-Al$$_{2}$$O$$_{3}$$(0001), we observed apparently contradicting results. The in-plane analysis shows that single-layer graphene grows not in the single-crystalline epitaxial manner but in the polycrystalline form with two strongly pronounced preferred orientations. This suggests the relatively weak interfacial interactions to be operative. But, we demonstrate that there exists unusually strong physical interactions between graphene and $$alpha$$-Al$$_{2}$$O$$_{3}$$(0001), as evidenced by the short vertical distance between graphene and $$alpha$$-Al$$_{2}$$O$$_{3}$$(0001) surface. The interfacial interactions are shown to be dominated by the electrostatic force involved in the graphene $$pi$$-system and the unsaturated electrons of the topmost O layer of $$alpha$$-Al$$_{2}$$O$$_{3}$$(0001) rather than the van der Waals interactions. Such feature causes hole doping into graphene, which gives graphene a chance to slide on the $$alpha$$-Al$$_{2}$$O$$_{3}$$(0001) surface with a small energy barrier despite the strong interfacial interactions.

論文

High hydrogen-adsorption-rate material based on graphane decorated with alkali metals

Antipina, L. Y.*; Avramov, P.; 境 誠司; 楢本 洋*; 大伴 真名歩; 圓谷 志郎; 松本 吉弘; Sorokin, P. B.*

Physical Review B, 86(8), p.085435_1 - 085435_7, 2012/08

 被引用回数:41 パーセンタイル:12.39(Materials Science, Multidisciplinary)

The graphane with chemically bonded alkali metals (Li, Na, K) was considered as potential material for hydrogen storage. The ab initio calculations show that such material can adsorb as many as four hydrogen molecules per Li, Na, and K metal atom. These values correspond to 12.20, 10.33, and 8.56 wt% of hydrogen, respectively, and exceed the DOE requirements. The thermodynamic analysis shows that Li-graphane complex is the most promising for hydrogen storage with ability to adsorb three hydrogen molecules per metal atom at 300 K and pressure in the range of 5-250 atm.

口頭

Interface atomic structure and interactions at graphene/insulator heterostructure

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; et al.

no journal, , 

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-Al$$_{2}$$O$$_{3}$$(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-Al$$_{2}$$O$$_{3}$$(0001) at the interface. The vertical distance between graphene and a-Al$$_{2}$$O$$_{3}$$(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.

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