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Evolution of Raman Spectra in Ion Irradiated MoS₂ Atomic Layers: Computational and Experimental Studies
Tanmay Mahanta1, Jyoti Shakya2, Tanuja Mohanty1
1School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067, India.
Abstract:
Herein we report the existence of biaxial strain in swift heavy ion irradiated Molybdenum disulfide (Mos₂) as confirmed from Raman spectroscopic measurement and computational study. Defect induced external strain modifies the electronic structure and phonon frequency of the material. In this work, chemically exfoliated Mos₂ nanosheets have been exposed to 70 MeV Ni+7 ion irradiation from varying fluence. The Raman spectra reveal that the defect induced LA(M) peak (longitudinal acoustic mode of Phonon at M point) evolves linearly with ion fluence, besides that several other new peaks appear and become visible in Raman spectra thus relaxing Raman fundamental selection rule. Theoretically, simulated Phonon dispersion also supports the fact that tensile strain results in the red shifting of the Raman peak position. The increment of the defect induced LA(M) peak intensity with increasing ion fluence could be a measure of defect quantitatively. This study will be beneficial in the application of external strain to engineer properties of Mos₂ as well as understanding the degree of strain inside it quantitatively.
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