Real-Time Observation of Photo-oxidation of Single MoS₂ Flakes Using Stochastic Optical Reconstruction Microscopy

Abstract

We report on molybdenum disulfide (MoS 2 ) flakes grown by chemical vapor deposition (CVD), which exhibit an increased photoluminescence (PL) intensity at the edge of the flake under moderate irradiation. The photo-induced chemisorption of O 2 and H 2 O to sulfur vacancies in the edge regions is the origin of the modulated PL intensity. The MoS 2 flakes were analyzed utilizing correlated multispectral wide-field microscopy with stochastic optical reconstruction microscopy (STORM). The advantage of the wide-field approach compared to conventional point scanning microscopy is a faster acquisition over a larger field of view without exposing the sample to high irradiance conditions. This enables in situ and realtime measurements of the PL intensity fluctuations and the identification of defects within the flake. The STORM postprocessing reveals fine structures within the flake and enhances the contrast, which cannot be revealed by point scanning microscopy. In particular, by increasing the intensity over the nondestructive threshold, the stochastic optical reconstruction enables the study of the kinetics of defect domain generation with reduced PL and Raman intensity caused by lattice defects or photo-oxidation of MoS 2 to MoO 3 . Additional measurements of the work function by Kelvin force microscopy, the topography, and the friction force by AFM reveal that the defect domains start to form at the edge of the flake, with a larger interlayer height and work function but reduced friction force compared to MoS 2 . The stochastic optical reconstruction microscopy postprocessing is a powerful technique to understand the layer-by-layer photo-oxidation of MoS 2 flakes and gives new insights in the design of, for example, MoS 2 /MoO 3 heterostructures.

Temperature-Dependent Phonon Scattering and Photoluminescence in Vertical MoS2/WSe2 Heterostructures

“…Remarkably, the photoluminescence maps obtained in this study demonstrate a stronger emission signal emanating from the MoS 2 monolayer, which can be ascribed to its elevated radiative recombination rate and binding energy. Importantly, these findings align with previous investigations of similar systems [ 34 ]. Moreover, photoluminescence measurements were conducted for both MoS 2 and WSe 2 in the monolayer position as well as the heterostructure region.…”

Tailoring gas sensing properties of WS2 monolayer via Nb and Co embedding for highly sensitive and selective detection of HCN and H2S gases: a first principle study

“…Nonetheless, the lack of a band gap in graphene impedes its practical application, necessitating the development of alternative materials with an appropriate band gap. Thus, following the pioneering discovery of graphene, a subsequent generation of two-dimensional (2D) materials expeditiously surfaced, encompassing hexagonal boron nitride (BN) [7], boron carbon nitride (BNC) [8], transition metal dichalcogenides [9,10], and functionalized graphene [11,12] have been extensively investigated. Due to their large surface-to-volume ratio, high thermal stability, and seamless compatibility with device integration, several experimental studies have investigated the ability of 2D materials for gas sensing [13,14].…”