Plasmonic Effect on the Magneto-Optical Property of Monolayer WS2 Studied by Polarized-Raman Spectroscopy

Wuguo Liu,Yuan Huang,Shibing Tian,Changzhi Gu,Huaqing Xue,Yang Yang,Zhongtao Lin,Junjie Li,Ke Zhu

doi:10.3390/app11041599

Abstract

In recent years, the magneto-optical properties of two-dimensional transition metal disulfides have attracted more and more attention due to their further device applications in spintronics and valleytronics. However, to our knowledge, the plasmonic effect on the magneto-optical properties of WS2 has not been studied. In this work, monolayer WS2 transferred on SiO2/Si substrate and Au film were investigated respectively using polarized-Raman spectroscopy at 4 K under different magnetic fields. Prominent magnetic field–induced variations in the Raman intensities of WS2 samples were observed, which also exhibited significant differences in the spectral evolution versus magnetic field. The resonance magnetic field was 5 T and 5.5 T for the WS2 on SiO2/Si substrate and Au film, respectively. Remarkably, the magneto-optical Raman intensities of A1′ and 2LA(M) modes for WS2 on Au film were reduced to approximately 60% compared with that of WS2 on SiO2/Si. These results suggest that the plasmonic effect–induced charge transfer plays an important role in the magneto-optical Raman effect of WS2.

Highlights

Received: 23 December 2020Two-dimensional (2D) transition metal disulfides (TMDs), which are composed of strong bonding layers with weak Van der Waals force interlayer attraction and can be stripped into separate atomic layers under certain conditions, have attracted extensive attention in the past 10 years because they exhibit extraordinary physical properties and extensive prospective applications in devices [1,2,3]
Lorentzians, five peaks are identified in the range of 250–450 cm−1 for the Raman spectra of WS2 /SiO2, which is consistent with previous literature [31]
Magneto-Raman spectroscopy has been successfully performed on monolayer WS2 transferred on SiO2 /Si substrate and Au film, respectively

Summary

Introduction

Two-dimensional (2D) transition metal disulfides (TMDs), which are composed of strong bonding layers with weak Van der Waals force interlayer attraction and can be stripped into separate atomic layers under certain conditions, have attracted extensive attention in the past 10 years because they exhibit extraordinary physical properties and extensive prospective applications in devices [1,2,3]. The transition from indirect band gap to direct band gap occurs when the thickness of WS2 decreases to monolayer [4]. Monolayer WS2 has a direct band gap with a theoretical value of ~2.1 eV [5], slightly larger than that of monolayer. The direct bandgap for monolayer WS2 opens up opportunities for the applications in electronic and optoelectronic devices, such as light-emitting diodes, photodetectors and photoelectric sensors [6,7]. WS2 has been considered as a natural candidate for valley research because of the unique symmetry and strong spin-orbit coupling [11]

Methods

Results

Conclusion