A seminar given by
Dr. Junji Yuhara,
professor at the School of Engineering, Nagoya University (Japan)
Fabrication and characterization of two-dimensional materials on solid surface
Abstract: In my research activities, I have been studying the following topics using variety of techniques such as LEED, AES, STM, LEIS, RBS, PES, and ARUPS; (a) binary metal adsorbates on Si(111) surface, (b) two dimensional alloy on metal surfaces, (c) intermetallic compound and metal oxide quasicrystals, (d) oxide surface and metal-oxide thin films on metal surfaces, (e) single crystal stainless steel surface, and (f) group 14 post-graphene materials. I will review some of these topics in this seminar.
- It has been studied for a decade that binary metal adsorbates on Si(111) surface induce a unique superstructure that is different from single metal adsorbate. In the case of lead and tin, they form a variety of superstructures, like √7×√3, √3×√3, and 2√7×3 structures, although lead and tin are immiscible in bulk . For the immiscible binary adsorbates of silver and copper on Si(111), Cu atoms behave a dissolution and segregation depending on the surface .
- To fabricate two-dimensional (2D) alloy, the substrate has to be static and inert against adsorbates. The 2D alloy is an overlayer monolayer film and should be incommensurate to the substrate. I succeeded in fabricating Pb-Sn 2D ordered 2D alloy and Pb-Bi solid solution 2D alloy for the first time using Rh(111) surface .
- I demonstrated to identify the Al surface segregation on an Al-Co-Ni and Al-Co-Cu decagonal quasicrystal surfaces and determine the atomic arrangement . Recently, oxide quasicrystal on Pt(111) has been prepared and structural properties are examined .
- The synthesis and characterization of post-graphene materials have been intensively studied with the aim of utilizing novel 2D properties. Most studies adopted molecular beam epitaxy as a synthesis method of 2D materials grown on clean crystalline surfaces. In my study, I will focus on the epitaxial growth of germanene, stanene, and plumbene on surface alloy and alloy surface by segregation and deposition methods.
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 J. Yuhara et al, Surf. Sci. 326, 133 (1995); J. Yuhara et al, Appl. Surf. Sci. 104/105, 163 (1996).
 J. Yuhara et al, Phys. Rev. B 67, 195407 (2003); J. Yuhara et al, J. of Appl. Phys. 110, 074314 (2011).
 J. Yuhara et al, Phys. Rev. B 70, 24203 (2004); R. Zenkyu et al, Phys. Rev. B 86, 115422 (2012).
 J. Yuhara et al, Phys. Rev. Mater. 4, 103402 (2020); Li et al, Appl. Surf. Sci. 561, 150099 (2021).
 J. Yuhara et al, ACS Nano 12, 11632 (2018); J. Yuhara et al, 2D Materials 5, 025002 (2018); J. Yuhara et al, Adv. Mater. 31, 1901017 (2019); J. Yuhara and G. Le Lay, Jpn. J. Appl. Phys. 59, SN0801 (2020); T. Ogikubo et al, Adv. Mater. Inter. 7, 1902132 (2020); W. Pang et al, Appl. Surf. Sci. 517, 146224 (2020); J. Yuhara et al, Appl. Surf. Sci. 550, 149236 (2021); J. Yuhara et al, Phys. Rev. Mater. 5, 053403 (2021); J. Yuhara et al, 2D Mater. 8, 045039 (2021); S. Mizuno et al, Appl. Phys. Express 14, 125501 (2021).
Bio: Junji Yuhara is currently associate professor at Department of Energy Science and Engineering at the Nagoya University. In 1995, he obtained a PhD in engineering at the Nagoya University, performing his research at Department of Crystalline Materials Science. He was visiting researcher in the USA, Austria and Singapore. His research focuses in the synthesis and characterization of 2D materials.