Efficient passivation of monolayer MoS₂ by epitaxially grown 2D organic crystals

Monolayer molybdenum disulfide (MoS₂) is considered to be a promising candidate for field-effect transistors and photodetectors due to its direct bandgap and atomically thin properties. However, the MoS₂ devices are impeded by the intrinsic surface defects and environmental adsorption such as H₂O and O₂. Here, we demonstrated a highly ordered, ultrathin (<5 nm) and scalable N,N'-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C13) passivation layer that can be epitaxially grown on MoS₂. The van der Waals interface between PTCDI-C13 and MoS₂ can efficiently reduce the surface traps and isolate MoS₂ from ambient. As a result, the passivated devices exhibit huge improvement in both carrier mobility (from 0.5 to 8.3 cm²/(V s)) and sub-threshold swing (from 16.7 to 1.6 V/dec). Also, the photodetector made on MoS₂ after passivation has a much faster response speed (from 3 s to 10 ms) without significant sacrifice of the responsivity. Our method provides a facile approach to realize high-performance two-dimensional electronic and optoelectronic devices.