Unveiling Defect-Related Raman Mode of Monolayer WS<sub>2</sub> via Tip-Enhanced Resonance Raman Scattering.

Lee, Chanwoo; Jeong, Byeong Geun; Yun, Seok Joon; Lee, Young Hee; Lee, Seung Mi; Jeong, Mun Seok · ACS Nano · 2018

basic_science · Level V

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Abstract

Monolayer tungsten disulfide (WS<sub>2</sub>) 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 WS<sub>2</sub>, the defect-related Raman scattering has been rarely studied. Here, we report the correlation of topography and Raman scattering in monolayer WS<sub>2</sub> by using tip-enhanced resonance Raman spectroscopy and reveal defect-related Raman modes denoted as D and D' modes. We found that the sulfur vacancies introduce not only the red-shifted A<sub>1g</sub> 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 WS<sub>2</sub> and will be helpful to improve the performance of WS<sub>2</sub> optoelectronic devices.