γ-ray Irradiation-Induced Chemical and Structural Changes in CVD Monolayer MoS<sub>2</sub>
Aditya Singh, Rajendra Singh
Abstract
Two dimensional (2D) materials are the ideal choice for highly efficient, lightweight, low power consumption nanoelectronics in space science applications. Therefore, investigation of radiation hardness of 2D-materials is of great interest. Herein, we report the effect of gamma irradiation on chemical vapor deposition (CVD) synthesized crystalline monolayer (1 L) molybdenum disulfide (MoS 2 ) flakes on the sapphire substrate at various doses, viz., 1–1000 kGy. We estimated that the temperature of MoS 2 increases by 1.3 °C per kGy of gamma-ray dose. It was observed that up to 130 kGy (∼195 °C), gamma exposure has no significant impact on the morphology and chemical properties of MoS 2 . However, X-ray photoelectron spectroscopy (XPS) shows that from 275 kGy (∼385 °C), MoS 2 starts converting into MoO x . Raman spectroscopy shows that at low gamma doses, the crystallinity of MoS 2 increases while at higher doses, a traceable amount of MoS 2 starts converting into amorphous MoS 3 . Our findings show that both E 1 2g and A 1g Raman mode of MoS 2 blue shift as gamma dose increases owing to the combined effect of sulfur vacancies creation and strain caused by thermal expansion of MoS 2 .