專題演講

2017/09/19(Tue)     14:00 -16:00    5th Floor(1st meeting room)

Title

Characterizations of Two-Dimensional Materials Surfaces

Speaker

Dr. Chun-Liang Lin

Department of Advanced Materials Science, The University of Tokyo

Abstract

Two-dimensional (2D) materials such as graphene, silicene, and transition metal dichalcogenides (TMDC) have become promising materials for next generation devices. Because of the huge diversity among them, to characterize their properties is thus an urgent issue. In this presentation, I will present the characterization of three different 2D materials surfaces though several surface techniques: 1. Silicene: the structure of single layer honeycomb structure consisting of Si grown on Ag(111) substrate is revealed by scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED) [1]. The quantum Hall effect (QHE) measurement of single layer silicene is also performed by scanning tunneling spectroscopy (STS) in high magnetic field up to 7T [2] as shown by Fig. 1. For multilayer silicene, the electronic structure of the outermost layer is identified by metastable atom electron spectroscopy (MAES) [3] as shown by Fig. 2. 2. Bi layered structure grown on Si(111) substrate: a strong peak different from the surface state is observed in STS spectra at the edge [4], which is similar to the one-dimensional topological edge state found on the cleaved bulk crystal of Bi along the [111] direction. In addition, the geometrical difference of two different types of edges is also confirmed by high resolution STM image. 3. Weyl semimetal (WTe2) surface: The surface structure of a TMDC semimetal, WTe2 is confirmed by LEED [5] and its topological electronic structure is observed by energy-dependent quasiparticle interference patterns (QPI) measured by STS. The results also well agree with prior theoretical predictions.