Effects of ambient gases on quantum emitters in hexagonal boron nitride monolayers

Defect-based quantum emitters (QEs) in hexagonal boron nitride (hBN) layers are being explored as sources of single-photons for quantum applications. However, most experiments report properties of QEs in bulk hBN crystals instead of hBN monolayers. This is due to a lack of photostability of defects in monolayers. Although the blinking and bleaching of defects are a serious bottleneck, the possible mechanisms behind these phenomena have not been explored. Using density functional theory we investigate the origins of the observed photo-instability. We find that it can be attributed to the interaction between defects in monolayer hBN and different ambient gases, such as nitrogen, oxygen and water vapor. These gases are mostly chemisorbed at the reactive defect sites, forming defect-gas composites with significantly different optical properties, resulting in the observed loss of photostability.