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1071-專題演講-1071212-唐述中(清華物理)

演講活動
張貼人:李明芳公告日期:2018-09-03
 
Time12/12/2018 (Wed.) 14:20~16:20
SpeakerProf.唐述中(Shu-Jung Tang)
                         Department of physics, National Tsing Hua University
TitleUncovering the germanene saga
Abstract
Two-dimensional (2D) honeycomb lattices beyond graphene promise new physical properties such as quantum spin Hall effect. While there have been claims of growth of such lattices (silicene, germanene, stanene), their existences need further supports and their preparation and characterization remain a difficult challenge. We provide definitive evidence that two distinct phases of germanene, the analog of graphene made of germanium (Ge) instead of carbon, can be grown on Ag(111) as observed by scanning tunneling microscopy (STM), low energy electron diffraction (LEED), and angle-resolved photoemission spectroscopy (ARPES). One such germanene exhibits an atom-resolved alternatively-buckled full honeycomb lattice, which is tensile strained and partially commensurate with the substrate to form a striped phase (SP). The other, a quasi-freestanding phase (QP), also exhibits a honeycomb lattice with a lattice constant incommensurate with the substrate but very close to the theoretical value for freestanding germanene. The SP, with a lower atomic density, can be driven into the QP and coexist with the QP by additional Ge deposition. Band mapping and first-principles calculations with proposed SP and QP models reveal an interface state exists only in the SP but the characteristic band of freestanding germanene emerges only in the QP this leads to an important conclusion that adlayer-substrate commensurability plays a key role to affect the electronic structure of germanene. The evolution of the dual germanene phases manifests the competitive formation of Ge-Ge covalent and Ge-Ag interfacial bonds.
In this talk, I would like to further illustrate a new idea of surfactant effects to effectively trigger the relaxation of tensile strain on SP to make it sharply transit to highly ordered QP via deposition of Pb atoms, as revealed by STM, LEED and ARPES. This result indeed opens a new possibility of growing a complete freestanding germanene where band (Dirac cone) exists. I will also trace the germanene formation back to its prequel, GeAg2 surface alloy, which exhibits anomalous splitting of surface states band at the surface zone boundary. The entire germanene growth on Ag(111) providing a vital insight in the growth of other 2D honeycomb lattices. 
PlaceConference Room (Basement), General Hall, Gongquan Campuses, NTNU


 
最後修改時間:2018-11-30 AM 9:21

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單位簡介

本系的重點研究領域包括:凝態物理、光電與奈米科學、高能與粒子物理、軟凝態物理與生物物理、原分子光學物理、及物理科學教育等。本系前身為臺灣省立師範學院理化系物理組,成立於民國三十五年(1946年)本校創校之始。民國五十一年(1962年)本系獨立成系,民國六十三年(1974年)成立物理研究所碩士班,民國八十年(1991年)成立研究所博士班。長久以來,本系肩負著培育臺灣中等學校物理科師資的重任,但也不忘在物理學術研究上求新求進步。至今本系培育出的學術人才已有一位中研院院士及近百位中研院研究員及大學教授,各行各業的高科技人材更是不勝枚舉。民國八十三年師資培育法改制後,本系已升級為尖端學術研究、科技應用研發、及中學師資培育三者齊備的系所。

  • 國立臺灣師範大學物理系系友會
  • 系友會線上小額捐款
  • 徐有庠盃-臺灣青年學生物理辯論競賽
  • 國際物理奧林匹亞競賽
  • BOSON CLUB
  • 公用場地與儀器設施預約系統
  • 學生實習專區
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