Optimization Strategies for High Photoluminescence Quantum Yield of Monolayer Chemical Vapor Deposition Transition Metal Dichalcogenides

Abstract

Chemical vapor deposition (CVD) is a promising method to obtain monolayer transition metal dichalcogenides (TMDCs) with high quality and enough size to meet the requirements of practical photoelectric devices. However, the as-grown monolayers often exhibit a lower PL performance due to the stress between the as-grown TMDCs flakes and the substrate. Therefore, finding a facile method to effectively promote the photoluminescence quantum yield (PL QY) of CVD monolayer TMDCs with a clean surface is highly desirable for practical applications. In this work, based on the CVD monolayers MoS2 and MoSe2, the effect of various stress relaxation methods on the TMDCs PL enhancement is systemically studied. By comparing the different kinds of volatile solution treatment processes, as well as the traditional transfer process, it can be found that the volatile solution with a moderate volatilization rate such as ethanol or IPA is a preferred option to improve the PL performance of the CVD monolayer TMDCs, which also surpasses the traditional transfer method by avoiding wrinkles, defects, and contamination to the samples. PL QY of ethanol-treated CVD samples could increase by 6 times on average. Significantly, PL QY of CVD MoSe2 treated by ethanol can reach ∼16%, which is at the forefront of the previous reports of 2D MoSe2. Our study demonstrated an optimized method to enhance the PL QY of CVD monolayer TMDCs, which would facilitate TMDCs optoelectronics.

Synaptic Plasticity and Visual Memory in a Neuromorphic 2D Memitter Based on WS2 Monolayers

“…In perspective, the here reported concept of 2D memitter can be introduced into a technological process flow by improving the lateral size of the deposited films (ideally to the wafer scale) and by boosting the quantum yield via interface engineering [52] or chemical methods, [53] thus aiming at expanding the matrix dimensions for VSTM applications by considering physical properties of other monolayer materials or intriguing combination of them in the heterostructure fashion, [54] where the spatial resolution of processable input patterns projected on the 2D material relies only on the laser spot size (Figure S5, Supporting Information). Furthermore, the rational design of 2D memitters can be developed by controlling and tuning the synaptic response by environmental conditions, laser excitation energy and power density.…”

Optical grade transformation of monolayer transition metal dichalcogenides via encapsulation annealing

“…As a reference sample, we utilized a thin poly(methyl methacrylate) (PMMA) film that contained dispersed rhodamine 6G (R6G). [43][44][45] We acquired photoluminescence (PL) spectra from a 300 nm-thick PMMA film with a concentration of 10 −4 M of R6G and from a bare quartz substrate. These spectra were measured utilizing an integrating sphere under a 514 nm laser excitation.…”

Chemical passivation of 2D transition metal dichalcogenides: strategies, mechanisms, and prospects for optoelectronic applications

“…Similarly, Chen et al demonstrated that the PLQYs of both MoS 2 and MoSe 2 were enhanced by the solvent with a moderate volatilization rate like ethanol. 132…”