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Because of profound applications of two-dimensional molybdenum disulfide (MoS2) and its heterostructures in electronics, its thermal stability has been spurred substantial interest. We employ a precision muffle furnace at a series of increasing temperatures up to 340 °C to study the oxidation behavior of continuous MoS2 films by either directly growing mono- and few-layer MoS2 on SiO2/Si substrate, or by mechanically transferring monolayer MoS2 or hexagonal boron nitride (h-BN) onto monolayer MoS2 substrate. Results show that monolayer MoS2 can withstand high temperature at 340 °C with less oxidation while the few-layer MoS2 films are completely oxidized just at 280 °C, resulting from the growth-induced tensile strain in few-layer MoS2. When the tensile strain of films is released by transfer method, the stacked few-layer MoS2 films exhibit superior thermal stability and typical layer-by-layer oxidation behavior at similarly high temperature. Counterintuitively, for the MoS2/h-BN heterostructure, the h-BN film itself stacked on top is not damaged and forms many bubbles at 340 °C, whereas the underlying monolayer MoS2 film is oxidized completely. By comprehensively using various experimental characterization and molecular dynamics calculations, such anomalous oxidation behavior of MoS2/h-BN heterostructure is mainly due to the increased tensile strain in MoS2 film at elevated temperature.
This work was financially supported by the National Natural Science Foundation of China (No. 52005489), Ningbo 3315 Innovation Team (No. 2020A-03-C), the China Postdoctoral Science Fund (Nos. 2021T140685 and 2019M662126), and the Natural Science Foundation of Zhejiang Province (No. LR20E050001).