Annealing Response of Monolayer MoS₂ Grown by Chemical Vapor Deposition

Abstract

Thermal stability of 2D materials under different conditions must be carefully examined since they can be submitted to heat during device fabrication and/or during application. In this work, the thermal stability of monolayer molybdenum disulfide (MoS2) under vacuum (∼10−7 mbar) annealing was investigated. While MoS2 bulk is stable up to 1050°C, monolayer MoS2 was only stable up to 700°C. At 800°C, significant degradation occurred, while at 900°C, all MoS2 was converted to MoO3 and MoO2. Results indicate that sulfur was lost during high temperature annealing, while no significant molybdenum loss was detected (no MoO3 evaporation occurred). Base pressure during annealing had a strong influence in the thermal degradation, since MoS2 was stable at 800°C when pressure was reduced to ∼10−9 mbar, while MoS2 was completely converted to MoO3 and MoO2 under 220 mbar of dry argon at 500°C, possibly due to the presence of oxidation agents. Results highlight the importance of the careful choice of conditions during growth and application of MoS2.