Junji Yuhara1
Nagoya University1
The synthesis and characterization of post-graphene materials have been intensively studied with the aim of utilizing novel two-dimensional (2D) properties. Most studies adopted molecular beam epitaxy as a synthesis method of 2D materials grown on clean crystalline surfaces. In my talk, I will talk on the epitaxial growth of (1) germanene, (2) stanene, and (3) plumbene by segregation and deposition methods [1–10].<br/>(1) <b>Germanene on Ag(111) thin film by segregation</b> [1]: On annealing the specimen of Ag(111) thin film grown on Ge(111)the Ge atoms segregate on the surface and germanene has been epitaxially formed on the surface. Low-energy electron diffraction clearly shows incommensurate “(1.3×1.3)”R30° spots, corresponding to a lattice constant of 0.39 nm, in perfect accord with close-up scanning tunneling microscopy (STM)images, which clearly reveal an internal honeycomb arrangement with corresponding parameter and low buckling within 0.01 nm. From the STM images, two types of protrusions, named hexagon and line, form a (7√7×7√7)R19.1° supercell with respect to Ag(111) with a super large periodicity of 5.35 nm.<br/>(2) <b>Stanene on Ag<sub>2</sub>Sn surface alloy by deposition</b> [2]: The lattice parameters of Ag<sub>2</sub>Sn surface alloy and free-standing stanene are close to each other. The Ag(111) easily react with Sn atoms on annealing, while the Ag<sub>2</sub>Sn surface alloy is chemically inert against the Sn atoms. Thus, the Ag<sub>2</sub>Sn surface alloy is physically and chemically ideal surface for epitaxial growth of stanene. We have successfully prepared large area planar stanene on Ag<sub>2</sub>Sn surface alloy by Sn deposition.<br/>(3) <b>Plumbene on Pd<sub>1-x</sub>Pb<sub>x</sub>(111) alloy surface by deposition and segregation </b>[3]: The bulk Pb-Pd system exists in fcc solid solution with a Pb concentration up to 10 ~ 17 %. 3he Pb atoms deposited dissolve into the Pd crystal and segregate on the surface on annealing. Through these process, plumbene is epitaxially grown on Pd<sub>1-x</sub>Pb<sub>x</sub>(111) surface. The surface also exhibits a unique morphology in the STM images resembling the famous Weaire-Phelan bubble structure of the Olympic “WaterCube” in Beijing.<br/> <br/>[1] J. Yuhara, H. Shimazu, K. Ito, A. Ohta, M. Araidai, M. Kurosawa, M. Nakatake, and G. Le Lay, ACS Nano <b>12</b>, 11632 (2018).<br/>[2] J. Yuhara, Y. Fujii, K. Nishino, N. Isobe, M. Nakatake, L. Xian, A. Rubio, and G. Le Lay, 2D Materials <b>5</b>, 025002 (2018).<br/>[3] J. Yuhara, B. He, N. Matsunami, M. Nakatake, and G. Le Lay, Adv. Mater. <b>31</b>, 1901017 (2019).<br/>[4] J. Yuhara and G. Le Lay, Jpn. J. Appl. Phys. <b>59</b>, SN0801 (2020).<br/>[5] T. Ogikubo, H. Shimazu, Y. Fujii, K. Ito, A. Ohta, M. Araidai, M. Kurosawa, G. Le Lay, and J. Yuhara, Adv. Mater. Interfaces <b>7</b>, 1902132 (2020).<br/>[6] W. Pang, K. Nishino, T. Ogikubo, M. Araidai, M. Nakatake, G. Le Lay, and J. Yuhara, Appl. Surf. Sci. <b>517</b>, 146224 (2020).<br/>[7] J. Yuhara, H. Shimazu, M. Kobayashi, A. Ohta, S. Miyazaki, S. Takakura, M. Nakatake, and G. Le Lay, Appl. Surf. Sci. <b>550</b>, 149236 (2021).<br/>[8] J. Yuhara, T. Ogikubo, M. Araidai, S. Takakura, M. Nakatake, and G. Le Lay, Phys. Rev. Materials <b>5</b>, 053403 (2021).<br/>[9] J. Yuhara, H. Muto, M. Araidai, M. Kobayashi, A. Ohta, S. Miyazaki, S. Takakura, M. Nakatake, and G. L. Lay, 2D Mater. <b>8</b>, 045039 (2021).<br/>[10] S. Mizuno, A. Ohta, T. Suzuki, H.Kageshima, J. Yuhara, H. Hibino, Appl. Phys. Express in press (2021)