Raman and X‐ray photoelectron spectroscopy investigation of the effect of gamma‐ray irradiation on MoS ₂

Abstract

The effect of gamma-ray (γ-ray) irradiation on the material characteristics of nanometre scale films of molybdenum disulphide (MoS 2) has been investigated. 3.2, 4.5, and 5.2 nm thick MoS 2 films (measured by atomic force microscopy) were grown on Si by using a two-step synthesis method (sputtering of Mo, followed by sulphurisation). The samples were subsequently exposed to γ-ray irradiation (dose of 120 MRad). Dramatic chemical changes in the MoS 2 films after irradiation were characterised by micro-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and optical microscopy. Micro-Raman spectroscopy showed the disappearance of the E 2g 1 and A 1g modes after irradiation. XPS revealed that the MoS 2 crystal structure was converted to molybdenum oxide (MoO x). It is hypothesised that S vacancies are formed due to the γ-ray irradiation, which subsequently transforms MoS 2 to MoO x .

Gamma Radiation-Induced Oxidation, Doping, and Etching of Two-Dimensional MoS2 Crystals

“…Importantly, similar features have been observed on the surface of gamma-irradiated few-layer MoS 2 films in the past. 38 To assess whether these circular features are aggregates containing products of MoS 2 radiolysis, a pristine SiO 2 /Si wafer was irradiated with a dose of 391 kGy in the absence of MoS 2 crystals. Optical micrographs show that circular features with similar contrast and morphology are formed on the SiO 2 surface after gamma irradiation ( Figure S6 , Supporting Information).…”

“…For example, Ozden et al utilized a 60 Co source to irradiate few-layer 2D MoS 2 films, produced by chemical vapor deposition (CVD), 37 with an absorbed dose of 1200 kGy under ambient conditions. 38 They observed the disappearance of the out-of-plane A 1g and in-plane E 2g 1 normal vibrational modes and the formation of MoO x species after irradiation, suggesting a significant increase in the chemical and structural disorder. Similarly, He et al also utilized a 60 Co source to irradiate MoS 2 , synthesized via a hydrothermal method, with absorbed doses between 1 kGy and 1000 kGy.…”

“…To the best of our knowledge, just a handful of studies have addressed the effects of the high-dose gamma irradiation of 2D MoS 2 . For example, Ozden et al utilized a 60 Co source to irradiate few-layer 2D MoS 2 films, produced by chemical vapor deposition (CVD), with an absorbed dose of 1200 kGy under ambient conditions . They observed the disappearance of the out-of-plane A 1g and in-plane E 2g 1 normal vibrational modes and the formation of MoO x species after irradiation, suggesting a significant increase in the chemical and structural disorder.…”

Recent Progress on Irradiation-Induced Defect Engineering of Two-Dimensional 2H-MoS2 Few Layers

“…Ozden et al [107] prepared MoS 2 multi-layers (5-8 layers) through the vapor phase sulfurization and exposed the layers to a γ-ray irradiation of 60 27 Co source (γ-ray energy: 1.1732 MeV and 1.3324 MeV) with a dose of 120 Mrad. The irradiation was carried out at room temperature in an ambient atmosphere.…”

Fast-neutron irradiation effects on monolayer MoS2

“…5) Tolerance to radiation and accompanying defect engineering are important considerations for the application of MoS 2 devices (e.g., as ultrathin transistors 6) and chemical sensors 7) ) in nuclear and space environments. Recently, the effects of ion irradiation, 8,9) laser irradiation, [10][11][12] and gamma-ray irradiation 13) on MoS 2 have been discussed. However, studies on neutron irradiation, [14][15][16] one of the most common types of irradiation, and the damage it causes to MoS 2 are still lacking.…”