Long-Term Exposure of MoS 2 to Oxygen and Water Promoted Armchair-to-Zigzag-Directional Line Unzippings.

Understanding the long-term stability of MoS 2 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 MoS 2 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 MoS 2 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 MoS 2 , the O 2 -treated MoS 2 primarily exhibits hole doping, whereas humid-O 2 -treated MoS 2 mainly exists in a neutral charge state with tension. This study provides a guideline for MoS 2 preservation and a further method for generating controlled defects.