Mechanical reliability of monolayer MoS2 and WSe2

Mechanical reliability reflects the survival (or equivalently, failure) probability of materials under loading and is critical for their long-term and device-scale applications. So far, the mechanical reliability of two-dimensional (2D) materials remains elusive and largely unexplored, especially in long-term loading conditions. Here, through more than 300 nanomechanical experiments and 1,200 molecular dynamics simulations, we evaluate the mechanical reliability of monolayer (1L) MoS2 and WSe2 under both monotonic tension and long-term static fatigue loading conditions. Weibull statistics reveal their mechanical reliability to resemble that of common engineering ceramics and soda-lime glass. We uncover that the observed low reliability results from the synergistic effect of thermal fluctuations, variations in defect configuration, and defect density. Finally, we establish that proof testing can be an effective approach to improve the mechanical reliability of 2D monolayers in practical applications.