Anomalous enhancement oxidation of few-layer MoS2 and MoS2/h-BN heterostructure

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.