Defects engineering and enhancement in optical and structural properties of 2D-MoS2 thin films by high energy ion beam irradiation

Abstract

Transition metal dichalcogenides (TMDs) like molybdenum disulfide (MoS2) have extra-ordinary physical and chemical peculiarities which can be additionally modified by ion beam irradiation. In the present work, we illustrate the tailoring of MoS2 thin films by employing ion beam irradiation. Silicon ion beam with 100 MeV energy was used to have an apparent impact on structural, morphological and optical properties of MoS2 thin films. Sputtered MoS2 films were irradiated with 100 MeV Si8+ ion beam with a fluence of 1E13 ions/cm2. The X-ray diffraction (XRD) technique validates the structural analysis of MoS2 films with hexagonal phase and reduction in the crystallinity is observed after irradiation owing to the generation of defects by high energy ion beam irradiation. MoS2 thin films display Raman modes at ⁓378 cm−1 and ⁓411 cm−1 corresponding to the one molybdenum atom and two sulfur atoms of the same layer vibrates in the converse in-plane and out-of-plane direction respectively. Intensity of Raman peaks is reduced after the employment of ion beam irradiation. Slight reduction in transmittance is observed after irradiation. The intensity of broad PL emission spectra observed at 360 nm showed the enhancement in PL intensity after ion beam irradiation. Rutherford backscattering spectroscopy (RBS) substantiated the presence of molybdenum (Mo) and sulfur (S) elements and 440 nm thickness of the samples. The investigation of the thickness and atomic fraction of the specimen was also governed by simulating the RBS spectrum using SIMNRA software. To demonstrate the changes occur in grain size and surface roughness parameters in ion irradiated and pristine MoS2 thin films were analyzed by AFM (atomic force microscopy). The alterations of binding energy of Mo 3d and S 2p region of MoS2 pristine and ion irradiated thin films were analyzed by X-ray photoelectron spectroscopy (XPS).