Substrate modified thermal stability of mono- and few-layer MoS2

Abstract

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 MoS₂. Triangular etching holes, which are considered to initiate from defect sites, form on MoS₂ when the temperature exceeds a threshold. On Al₂O₃ and SiO₂, monolayer MoS₂ is found to be more stable in thermal annealing than few-layer MoS₂ 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 MoS₂ samples. The substrate modification of the thermal stability of MoS₂ with various thicknesses is attributed to the competition between MoS₂–substrate interface interaction and MoS₂–MoS₂ interlayer interaction. Our findings provide important design rules for MoS₂-based devices, and also potentially point to a route of controlled patterning of MoS₂ with substrate engineering.