Probing defect dynamics in monolayer MoS2 via noise nanospectroscopy

Monolayer molybdenum disulfide (MoS 2 ) has received intense interest as a strong candidate for next-generation electronics. However, the observed electrical properties of monolayer MoS 2 exhibit several anomalies: samples universally exhibit unexpectedly low mobilities, n-type characteristics, and large contact resistances regardless of contact metal work function. These anomalies have been attributed to the presence of defects, but the mechanism behind this link has been elusive. Here we report the ionization dynamics of sulfur monovacancy defects in monolayer MoS 2 probed via noise nanospectroscopy, realized by combining noise–current analysis with atomic force microscopy. Due to the nanoscale dimension of the in situ channel defined by the tip size, we probe a few monovacancy defects at a time. Monovacancy defects exhibit switching between three distinct ionization configurations, corresponding to charge states 0, −1, and −2. The most probable charge configurations are 0 and −1, providing a plausible mechanism to explain the observed anomalies of MoS 2 monolayers. The intrinsic properties of atomically thin MoS 2 are believed to be strongly affected by the presence of structural defects; however, the underlying physical mechanism of such link is not fully understood. Here, the authors combine noise-current analysis with atomic force microscopy to explore the relationship between point defects and the anomalous physical properties of MoS 2 monolayers.