Abstract

Ultraviolet-ozone (UV-O₃) treatment is a simple but effective technique for surface cleaning, surface sterilization, doping and oxidation, and is applicable to a wide range of materials. In this study, we investigated how UV-O₃ treatment affects the optical and electrical properties of molybdenum disulfide (MoS₂), with and without the presence of a dielectric substrate. We performed detailed photoluminescence (PL) measurements on 1-7 layers of MoS₂ with up to 8 minutes of UV-O₃ exposure. Density functional theory (DFT) calculations were carried out to provide insight into oxygen-MoS₂ interaction mechanisms. Our results showed that the influence of UV-O₃ treatment on PL depends on whether the substrate is present, as well as the number of layers. The PL intensity of the substrate-supported MoS₂ decreased dramatically with the increase of UV-O₃ treatment time and was fully quenched after 8 mins. However, the PL intensity of the suspended flakes was less affected. 4 minutes of UV-O₃ exposure was found to be optimal to produce p-type MoS2, while maintaining above 80% of the PL intensity and the emission wavelength, compared to pristine flakes (intrinsically n-type). Our electrical measurements showed that UV-O₃ treatment for more than 6 minutes not only caused a reduction in the electron density but also deteriorated the hole-dominated transport. It is revealed that the substrate plays a critical role in the manipulation of the electrical and optical properties of MoS2, which should be considered in future device fabrication and applications.

Abstract

Ultraviolet-ozone (UV-O₃) treatment is a simple but effective technique for surface cleaning, surface sterilization, doping and oxidation, and is applicable to a wide range of materials. In this study, we investigated how UV-O₃ treatment affects the optical and electrical properties of molybdenum disulfide (MoS₂), with and without the presence of a dielectric substrate. We performed detailed photoluminescence (PL) measurements on 1-7 layers of MoS₂ with up to 8 minutes of UV-O₃ exposure. Density functional theory (DFT) calculations were carried out to provide insight into oxygen-MoS₂ interaction mechanisms. Our results showed that the influence of UV-O₃ treatment on PL depends on whether the substrate is present, as well as the number of layers. The PL intensity of the substrate-supported MoS₂ decreased dramatically with the increase of UV-O₃ treatment time and was fully quenched after 8 mins. However, the PL intensity of the suspended flakes was less affected. 4 minutes of UV-O₃ exposure was found to be optimal to produce p-type MoS2, while maintaining above 80% of the PL intensity and the emission wavelength, compared to pristine flakes (intrinsically n-type). Our electrical measurements showed that UV-O₃ treatment for more than 6 minutes not only caused a reduction in the electron density but also deteriorated the hole-dominated transport. It is revealed that the substrate plays a critical role in the manipulation of the electrical and optical properties of MoS2, which should be considered in future device fabrication and applications.

Abstract

Ultraviolet-ozone (UV-O₃) treatment is a simple but effective technique for surface cleaning, surface sterilization, doping and oxidation, and is applicable to a wide range of materials. In this study, we investigated how UV-O₃ treatment affects the optical and electrical properties of molybdenum disulfide (MoS₂), with and without the presence of a dielectric substrate. We performed detailed photoluminescence (PL) measurements on 1-7 layers of MoS₂ with up to 8 minutes of UV-O₃ exposure. Density functional theory (DFT) calculations were carried out to provide insight into oxygen-MoS₂ interaction mechanisms. Our results showed that the influence of UV-O₃ treatment on PL depends on whether the substrate is present, as well as the number of layers. The PL intensity of the substrate-supported MoS₂ decreased dramatically with the increase of UV-O₃ treatment time and was fully quenched after 8 mins. However, the PL intensity of the suspended flakes was less affected. 4 minutes of UV-O₃ exposure was found to be optimal to produce p-type MoS2, while maintaining above 80% of the PL intensity and the emission wavelength, compared to pristine flakes (intrinsically n-type). Our electrical measurements showed that UV-O₃ treatment for more than 6 minutes not only caused a reduction in the electron density but also deteriorated the hole-dominated transport. It is revealed that the substrate plays a critical role in the manipulation of the electrical and optical properties of MoS2, which should be considered in future device fabrication and applications.

Abstract

Ultraviolet-ozone (UV-O₃) treatment is a simple but effective technique for surface cleaning, surface sterilization, doping and oxidation, and is applicable to a wide range of materials. In this study, we investigated how UV-O₃ treatment affects the optical and electrical properties of molybdenum disulfide (MoS₂), with and without the presence of a dielectric substrate. We performed detailed photoluminescence (PL) measurements on 1-7 layers of MoS₂ with up to 8 minutes of UV-O₃ exposure. Density functional theory (DFT) calculations were carried out to provide insight into oxygen-MoS₂ interaction mechanisms. Our results showed that the influence of UV-O₃ treatment on PL depends on whether the substrate is present, as well as the number of layers. The PL intensity of the substrate-supported MoS₂ decreased dramatically with the increase of UV-O₃ treatment time and was fully quenched after 8 mins. However, the PL intensity of the suspended flakes was less affected. 4 minutes of UV-O₃ exposure was found to be optimal to produce p-type MoS2, while maintaining above 80% of the PL intensity and the emission wavelength, compared to pristine flakes (intrinsically n-type). Our electrical measurements showed that UV-O₃ treatment for more than 6 minutes not only caused a reduction in the electron density but also deteriorated the hole-dominated transport. It is revealed that the substrate plays a critical role in the manipulation of the electrical and optical properties of MoS2, which should be considered in future device fabrication and applications.