  Two-dimensional (2D) transition metal dichalcogenides (TMDCs) are the subject
of intense investigation for applications in optics, electronics, catalysis,
and energy storage. Their optical and electronic properties can be
significantly enhanced when encapsulated in an environment that is free of
charge disorder. Because hexagonal boron nitride (h-BN) is atomically thin,
highly-crystalline, and is a strong insulator, it is one of the most commonly
used 2D materials to encapsulate and passivate TMDCs. In this report, we
examine how ultrathin h-BN shields an underlying MoS2 TMDC layer from the
energetic argon plasmas that are routinely used during semiconductor device
fabrication and post-processing. Aberration-corrected Scanning Transmission
Electron Microscopy is used to analyze defect formation in both the h-BN and
MoS2 layers, and these observations are correlated with Raman and
photoluminescence spectroscopy. Our results highlight that h-BN is an effective
barrier for short plasma exposures (< 30 secs) but is ineffective for longer
exposures, which result in extensive knock-on damage and amorphization in the
underlying MoS2.
