[Distinguished Lecture Series]

Nov. 27^th Wed. 2019, 4:30pm
N Center #86120, Sungkyunkwan University, Suwon

Cross-sectional transmission electron microscopy for revealing the

interface structure of 2D transition metal dichalcogenides (TMDs)

Prof. Hu Young Jeong

UNIST Central Research Facilities (UCRF) & School of Materials Science and Engineering, UNIST

Abstract

Transmission Electron Microscopy (TEM) has been considered as a powerful technique to investigate the structural, chemical, and electronic properties of materials. Recently, the advanced TEM equipped with a spherical aberration corrector was introduced and actively used for uncovering the atomic-scale structure and chemical composition of nano-materials with various dimensions (from 0D to 3D) in a sub-Å level. Owing to keeping the high resolution even at a low-kV electron energy, we can characterize the low atomic number elements such as C, N, and O which are main chemical composition of the two-dimensional (2D) materials. In the real optical and electronic devices, revealing the interface structure found at the regions between metal and 2D material or among different 2D materials is so crucial for improving the performance of future devices. In this case, the cross-sectional TEM analysis combined well-prepared TEM samples is needed. In this presentation, I will introduce the various cross-sectional TEM researches which were performed using a Cs corrected TEM installed in UNIST combined with a focused ion beam (FIB) sample preparation technique. Among these results, I will focus the interface analysis which are crucial for revealing the scientific and fundamental phenomena found at the interface between metal(In/Au) and 2D semiconductors (transitional metal dichalcogenides; MoS2) for the future application of electronic devices. In addition, metallic 2H phase of niobium disulfide (Nb1+XS2) with additional niobium atoms for potential hydrogen revolution reaction (HER) catalysts were clearly visualized via cross-sectional scanning TEM (STEM) images.

References

[1] Y. Wang et al., Nature 568, 70-74 (2019).

[2] J. Yang et al. Nat. Mater. In press (2019).

Brief Bio

Hu Young Jeong received his PhD. from the Department of Materials Science and Engineering of Korea Advanced Institute of Science and Technology (KAIST) in 2010. Now he is an associate professor at UNIST Central Research Facilities (UCRF) and School of Materials Science and Engineering, Ulsan National Institute Science and Technology (UNIST). His research interests include structural and chemical characterization of various nano-materials using advanced transmission electron microscope (TEM) such as a spherical-aberration (Cs) corrected TEM.