Long-Term Exposure of MoS2 to Oxygen and Water Promoted Armchair-to-Zigzag-Directional Line Unzippings

Abstract

Understanding the long-term stability of MoS2 is important for various optoelectronic applications. Herein, we show that the long-term exposure to an oxygen atmosphere for up to a few months results in zigzag (zz)-directional line unzipping of the MoS2 basal plane. In contrast to exposure to dry or humid N-2 atmospheres, dry O-2 treatment promotes the initial formation of line defects, mainly along the armchair (ac) direction, and humid O-2 treatment further promotes ac line unzipping near edges. Further incubation of MoS2 for a few months in an O-2 atmosphere results in massive zz-directional line unzipping. The photoluminescence and the strain-doping plot based on two prominent bands in the Raman spectrum show that, in contrast to dry-N-2-treated MoS2, the O-2-treated MoS2 primarily exhibits hole doping, whereas humid-O-2-treated MoS2 mainly exists in a neutral charge state with tension. This study provides a guideline for MoS2 preservation and a further method for generating controlled defects.