Effect of Ar-ion irradiation on electrical transport of WS2 monolayer

Abstract

Two-dimensional transition metal dichalcogenides (2D-TMDs), such as WS2 and MoS2, have attracted exceptional attention as promising materials for future optoelectronic systems due to their unique properties, including a direct band gap, high quantum efficiency, and flexibility. However, exploiting these materials’ potential in their pristine state remains a key challenge because of limited tunability and control over their properties. The introduction of crystal defects, such as vacancies and dopants, induces localized mid-gap states in 2D materials, enhances electrical transport, and creates a platform for tuning and exploiting these materials for practical applications. Our study explores the effect of Ar-ion beam irradiation on monolayer WS2, resulting in enhanced electrical transport compared to the pristine sample. We regulated the Ar-ion bombardment energy to vary the defect concentration from 0.1 to 0.5 keV. Photoluminescence (PL) and Raman investigations, revealed the extent of damage to the material. At the same time, x-ray photoelectron spectroscopy showed changes in the oxidation state with increasing irradiation energy. Our results demonstrated that Ar-ion treatment at low-energy irradiation enhanced electrical transport by ∼12 fold compared to pristine till 0.2 keV of irradiation by incorporating defects. However, higher irradiation energies reduced electrical transport due to increased disorder in the WS2 monolayer. This investigation highlights the potential for controlled defect engineering to optimize the properties of 2D-TMDs for practical applications.