Two-dimensional semiconducting transition metal dichalcogenides have been employed as key components in various electronic devices. The thermal stability of these ultrathin materials must be carefully considered in device applications because the heating caused by current flow, light absorption, or other harsh environmental conditions is usually unavoidable. In this work, we found that the substrate plays a role in modifying the thermal stability of mono- and few-layer MoS. Triangular etching holes, which are considered to initiate from defect sites, form on MoS when the temperature exceeds a threshold. On AlO and SiO, monolayer MoS is found to be more stable in thermal annealing than few-layer MoS either in atmospheric-pressure air or under vacuum; while on mica, the absolute opposite behavior exists. However, this difference due to substrates appears to vanish when using defective, chemical-vapor-deposited MoS samples. The substrate modification of the thermal stability of MoS with various thicknesses is attributed to the competition between MoS-substrate interface interaction and MoS-MoS interlayer interaction. Our findings provide important design rules for MoS-based devices, and also potentially point to a route of controlled patterning of MoS with substrate engineering.
Two-dimensional (2D) materials have attracted growing attention since the discovery of graphene [1]. Transition metal dichalcogenide (TMD) semiconductors, such as MoS 2 and WS 2 , became popular materials in recent years, because they usually have intrinsic bandgaps and an indirect-to-direct bandgap transition from bulk to monolayer limit [2][3][4][5][6]. Although graphene and TMDs are promising materials in field-effect devices [7][8][9], their heterostructures are more advanced in charge-splitting functions for the applications in optoelectronic devices [10][11][12][13][14][15]. In these heterostructure devices, graphene has been utilized as an effective electrode to reduce the contact resistance in 2D semiconductor devices due to its ultra-flat surface, high carrier mobility, and gate-tunable Fermi level. The diversity of 2D semiconductors has also enabled 2D heterostructures with multiple functionalities to meet various demands in applications [16][17][18][19][20][21].Modulation of 2D heterostructure properties is desired for their diverse applications. Defect engineering of materials, which can be achieved by irradiation of particles such as electrons or ions, provides an effective way to modulate properties of materials, as proven in silicon industry. Currently, diverse irradiation sources, including argon ions (Ar + ) [22,23] [22], and an improvement in electrical conductivity after a mild oxygen treatment in MoS 2 [32]. It has been shown that upon electron irradiation, 2D TMDs can be modified with vacancy defects and doped by filling the vacancies with impurity atoms [25], and graphene is also doped with electrons or holes depending on the irradiation energy [26]. So far these effects of irradiation have been mostly investigated in single 2D materials. Effects of irradiation on 2D heterostructures have yet to be well explored, and whether the build-up of 2D heterostructures could circumvent the degradation of the materials remains a question.In this work, we found that the build-up of heterostructures could partly hinder the degradation of the properties of monolayer MoS 2 against electron irradiation damage. By insertion of a monolayer graphene between MoS 2 and the substrate, the photoluminescence (PL) from MoS 2 /graphene heterostructure area is always stronger in intensity and more robust in energy under electron irradiation, in contrast to the dramatic PL shift in the MoS 2 monolayer area. The improvement is attributed to a blocking effect of graphene that prevents MoS 2 from being affected by the substrate. Raman spectra and electrical transfer properties were also investigated to systematically reveal the effect of electron irradiation on the MoS 2 /graphene heterostructure. Our work not only deepens the understanding of irradiation effects on 2D heterostructures, but also paves the way to the design of novel irradiation-resistant devices.Electron irradiation exists commonly in environments ranging from materials observation under electron mi-
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.