Photoluminescence Quenching in Single-Layer MoS₂ via Oxygen Plasma Treatment

Abstract

By creating defects via oxygen plasma treatment, we demonstrate optical properties variation of single-layer MoS 2 . We found that, with increasing plasma exposure time, the photoluminescence (PL) evolves from very high intensity to complete quenching, accompanied by gradual reduction and broadening of MoS 2 Raman modes, indicative of distortion of the MoS 2 lattice after oxygen bombardment. X-ray photoelectron spectroscopy study shows the appearance of Mo 6+ peak, suggesting the creation of MoO 3 disordered regions in the MoS 2 flake. Finally, using band structure calculations, we demonstrate that the creation of MoO 3 disordered domains upon exposure to oxygen plasma leads to a direct to indirect bandgap transition in single-layer MoS 2 , which explains the observed PL quenching. KEYWORDS 2D materials, defect engineering, optical properties, bandgap tuning, molybdenum trioxide INTRODUCTIONThe ability to controllably tailor the properties of a material is a key factor in the development of many novel applications. In the case of bulk semiconductors, creating and manipulating defects constitutes an essential element in controlling the electrical, magnetic, and optical properties of the host material. 1 Although the role of defects is well understood in bulk semiconductors, it has received little attention in emerging two-dimensional (2D) layered semiconductors, preventing their full exploitation for tailored 2D nanoelectronic and photonic devices. Graphene and graphene oxide are examples of the impact that defects can have on 2D materials. Pristine graphene, which contains no intrinsic defect, is well known for its extraordinary high mobility, and is of great importance for high frequency device applications. 2, 3 However, its inherent lack of bandgap and low absorption of solar photons greatly limit its use in electronic and photonic devices. On the other hand, its solution processed counterparts, graphene oxide and reduced graphene oxide, have a large amount of defects, which lead to formation of a bandgap and open the way to many other applications in photodetectors, sensors, catalysis, and solar cell. [4][5][6][7][8] Recently, layered transition metal dichalcogenides (TMDs) have emerged as important materials for 2D device engineering. 9-11 Molybdenum disulfide (MoS 2 ), composed of weak van der Waals bonded S-Mo-S units, offers a large intrinsic bandgap that is strongly dependent on the number of layers, with an indirect bandgap (1.2 eV) in bulk MoS 2 transitioning to a direct

Defective MoS2 electrocatalyst for highly efficient hydrogen evolution through a simple ball-milling method

“…Consequently, the position of A 1g mode blue shifts about 1.02 cm −1 , while E 1 2g mode blue shifts about 1.84 cm −1 . The Raman spectra confirms lattice distortion [38]. Furthermore, intensity of the DRMoS 2 PL peak (680 nm) also decreases compared to BMMoS 2 , as shown in Fig.…”

Recent development in 2D materials beyond graphene

“…In the same way, long-range antiferromagnetic properties showed in H-engrossed MoSe 2 , MoTe 2 and WS 2 single layers and F-engrossed MoSe 2 and WS 2 single layers [367]. Tuning the electrical properties of single layer MoS 2 via defect engineering have been explored by oxygen plasma treatment [368,369].…”

Impact of N-plasma and Ga-irradiation on MoS2 layer in molecular beam epitaxy

“…However, the effect of N Ã 2 -and Ga-irradiation on the 2D layered-MoS 2 in high to ultra-high vacuum (UHV) environment has not been explored. Focusing on MoS 2 , the tunability of doping, [13][14][15][16][17] optical, [18][19][20] and structural, 21 properties of the layered-MoS 2 has been reported by employing the plasma (O Ã 2 or N Ã 2 ) irradiation. However, in most of these studies, $150 Torr of the background utilized during plasma irradiation, whereas in plasma-assisted MBE (PAMBE), low background $10 À6 Torr can be used for tuning the properties of layered-MoS 2 .…”