Long-term stability of multilayer MoS₂ transistors with mica gate dielectric

To avoid surface damage of a MoS₂ channel, a mica flake with high permittivity and atomically flat surface was dry transferred onto a multilayer MoS₂ flake to prepare top-gated transistors. For the first time, the interface properties of mica/MoS₂ and the long-term stability of devices were investigated when the transistors were exposed to ambient air. Results show that the electrical performance of the transistors is degraded significantly when the devices are exposed to ambient moisture for a long time, due to the strong hydrophilism of mica. The transfer curves of the transistors cannot be recovered to their initial states even after annealing. The adsorbed moisture can become trapped at the interface between the MoS₂ channel and mica dielectric or on the MoS₂ surface, resulting in enhanced carrier scattering and degraded device performance. However, the top-gated MoS₂ transistor with Al₂O₃ encapsulation exhibits enhanced stability even after annealing or exposure to atmosphere for 200 days. The excellent stability should be attributed to the effective insulation of moisture from the ambient air by Al₂O₃ encapsulation. Therefore, a dense and hydrophobic encapsulation layer is indispensable for stable and high-performance top-gated MoS₂ transistors with mica gate dielectric.