2D TMDC aging: a case study of monolayer WS₂and mitigation strategies

Due to their unique properties, two-dimensional transition metal dichalcogenides (2D TMDCs) are considered for diverse applications in microelectronics, sensing, catalysis, to name a few. A common challenge in 2D TMDC research is the film's inherent instability i.e. spontaneous oxidation upon ambient exposure. The present study systematically explores the effect aging on the film composition and photoluminescent properties of monolayer WS₂, synthetically grown by metal-organic chemical vapor deposition. The aging rate is investigated for different oxygen- (i.e. O₂gas concentration and humidity) and light-controlled environments. Simple mitigation strategies that do not involve capping the 2D TMDC layer are discussed, and their effectiveness demonstrated by benchmarking the evolution in photoluminescence response against ambient exposed monolayer WS₂. These results highlight the need to store 2D TMDCs in controlled environments to preserve the film quality and how future studies can account for the aging effect.