Contracted interlayer distance in graphene/sapphire heterostructure

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

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

https://doi.org/10.1007/s12274-014-0640-7

Contact-induced spin polarization of monolayer hexagonal boron nitride on Ni(111)

Otomo, Manabu; Yamauchi, Yasushi*; Kuzubov, A. A.*; Eliseeva, N. S.*; Avramov, P.*; Entani, Shiro; Matsumoto, Yoshihiro; Naramoto, Hiroshi*; Sakai, Seiji

Applied Physics Letters, 104(5), p.051604_1 - 051604_4, 2014/02

https://doi.org/10.1063/1.4863324

Hexagonal boron nitride (h-BN) is a promising barrier material for graphene spintronics. In this study, spin-polarized metastable de-excitation spectroscopy (SPMDS) is employed to study the spin-dependent electronic structure of monolayer h-BN on Ni(111). The extreme surface sensitivity of SPMDS enables us to elucidate a partial filling of the in-gap states of h-BN without any superposition of Ni 3 signals. The in-gap states are shown to have a considerable spin polarization parallel to the majority spin of Ni. The positive spin polarization is attributed to the - hybridization and the effective spin transfer to the nitrogen atoms at the h-BN/Ni(111) interface.

In-plane orientation control of 2,7-diphenyl[1]benzothieno[3,2-][1]benzothiophene monolayer on bismuth-terminated Si(111) vicinal surfaces with wettability optimization

Otomo, Manabu; Tsuchida, Yuya*; Muraya, Naoki*; Yanase, Takashi*; Sakai, Seiji; Yonezawa, Tetsu*; Nagahama, Taro*; Hasegawa, Tetsuya*; Shimada, Toshihiro*

Journal of Physical Chemistry C, 117(22), p.11555 - 11561, 2013/06

https://doi.org/10.1021/jp3117837

We report in-plane orientation control of newly developed high-mobility organic semiconductor: 2,7-diphenyl[1]benzothieno[3,2-][1]benzothiophene (DPh-BTBT). As previously reported on monolayer pentacene, it was revealed that bunched steps on vicinal Si(111) with bismuth termination break the surface symmetry and reduce three-fold symmetry of DPh-BTBT grains into quasi-single orientation. Interestingly, the critical step height necessary for the orientation control was different from that of pentacene. We examined several mechanisms of orientation control and concluded that the facet nano structure fabricated by step bunching is working as an anisotropic template. We will also show the wettability control of bismuth terminated silicon surface and show that the growth mode of DPh-BTBT is dependent on the surface nanostructure of Bi-Si.

Contact-induced spin polarization in graphene/-BN/Ni nanocomposites

Avramov, P.; Kuzubov, A. A.*; Sakai, Seiji; Otomo, Manabu; Entani, Shiro; Matsumoto, Yoshihiro; Naramoto, Hiroshi*; Eliseeva, N. S.*

Journal of Applied Physics, 112(11), p.114303_1 - 114303_10, 2012/12

https://doi.org/10.1063/1.4767134

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

Antipina, L. Y.*; Avramov, P.; Sakai, Seiji; Naramoto, Hiroshi*; Otomo, Manabu; Entani, Shiro; Matsumoto, Yoshihiro; Sorokin, P. B.*

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

https://doi.org/10.1103/PhysRevB.86.085435

Precise control of single- and bi-layer graphene growths on epitaxial Ni(111) thin films

Entani, Shiro; Matsumoto, Yoshihiro; Otomo, Manabu; Avramov, P.; Naramoto, Hiroshi*; Sakai, Seiji

Journal of Applied Physics, 111(6), p.064324_1 - 064324_6, 2012/03

https://doi.org/10.1063/1.3694662

analysis was performed on the graphene growth in ultrahigh vacuum chemical vapor deposition by exposing the epitaxial Ni(111) thin film to benzene vapor at 873 K. It is shown that the highly uniform single- and bi-layer graphenes can be synthesized by the control of benzene exposure in the range of 10-10 langmuirs, reflecting a change in the graphene growth-rate by three orders of magnitude in between the first and second layer. Electron energy loss spectroscopy measurements of single- and bi-layer graphenes indicates that the interface interaction between bi-layer graphene and Ni(111) is weakened in comparison with that between single-layer graphene and Ni(111). It is also clarified from the micro-Raman analysis that the structural and electrical uniformities of the graphene film transformed on a SiO substrate are improved remarkably under the specific exposure conditions at which the growths of single- and bi-layer graphenes are completed.

Growth of highly uniform graphene for spintronic applications

Entani, Shiro; Matsumoto, Yoshihiro; Otomo, Manabu; Avramov, P.; Naramoto, Hiroshi*; Sakai, Seiji

no journal, , 

Potential energy surfaces of He and Ni migration and clusterization on quasi-metallic armchair graphene nanoribbons

Avramov, P.; Sakai, Seiji; Entani, Shiro; Matsumoto, Yoshihiro; Otomo, Manabu; Kuzukov, A.*; Naramoto, Hiroshi*

no journal, , 

The atomic and electronic structures and spin states of helium and nickel nanocusters on metallic armchair graphene nanoribbons were studied using ab initio PBC/HSE technique. To reproduce the electronic and band structure of graphene, quasi-metallic armchair nanoribbons of different width and length with 0.05-0.15 eV band gaps were used as structural models. To study the mechanisms of clusterization of helium and nickel atoms on graphene, the potential energy surfaces of He and Ni migration were calculated using elastic membrane and absolutely rigid substrate approximations. It was found that the eta 6 coordination of He and Ni atoms is the only one energetically favorable position of the absorbed single atoms on graphene. The potential energy barriers of dissociation, regrouping and clusterization of the atoms were calculated.

Precise control of graphene layer number

Entani, Shiro; Matsumoto, Yoshihiro; Otomo, Manabu; Avramov, P.; Naramoto, Hiroshi*; Sakai, Seiji

no journal, , 

no abstracts in English

Graphene growth on Ni(111) and Cu(111) thin films and its electric properties

Entani, Shiro; Matsumoto, Yoshihiro; Otomo, Manabu; Avramov, P.; Naramoto, Hiroshi*; Sakai, Seiji

no journal, , 

no abstracts in English