Colloquium

  • Diagnosis of Defects in 2D Nanomaterials with Vibrational Nanoscopy

  • Speaker : 정문석(Mun Seok Jeong)
    Affiliation : Sungkyunkwan University
    Date : May 29, 2019 4:00 PM
    Place : Bldg.110 Room N103
    Contact : kdpark@unist.ac.kr
    Host : 박경덕(Kyoung-Duck Park)
  • Abstract

  • In this presentation, analysis of 2D nanomaterials with Tip enhanced Raman scattering (TERS) will be provided. TERS is a unique tool for investigating Raman scattering mapping with nanometer spatial resolution beyond optical diffraction limit. Using representative tips fabricated under the optimal etching condition, Our lab. demonstrate the TERS experiment of tungsten disulfide (WS2) monolayer grown by a chemical vapor deposition method with a spatial resolution of ~40 nm. Monolayer WS2 has emerged as an active material for optoelectronic devices due to its quantum yield of photoluminescence. Despite the enormous research about physical characteristics of monolayer WS2, the defect-related Raman scattering has been rarely studied. In this work, we report the correlation of topography and Raman scattering in monolayer WS2 by using TERS and reveal defect-related Raman modes denoted as D and D′ modes. We found that the sulfur vacancies introduce not only the red-shifted A1g mode but also the D and D′ modes by the density functional theory calculations. The observed defect-related Raman modes can be utilized to evaluate the quality of monolayer WS2 and will be helpful to improve the performance of WS2 optoelectronic devices.

     

    1. Kyoung-Duck Park & M.S. Jeong* et al “Probing Bilayer Grain Boundaries in Large Area Graphene with Tip-Enhanced Raman Spectroscopy”, Advanced Materials, 29, 1603601(2017)
    2. Chanwoo Lee & M.S. Jeong* et al “Tip-Enhanced Raman Scattering Imaging of Two-Dimensional Tungsten Disulfide with Optimized Tip Fabrication Process“, Scientific Reports, 7, 40810 (2017).
    3. Chanwoo Lee & M.S. Jeong* et al “Unveiling defect-related Raman mode of monolayer WS2 via tip-enhanced resonance Raman scattering “, ACS Nano, 12, 10, 9982-9990(2018)