Nano-patterning on multilayer MoS₂ via block copolymer lithography for highly sensitive and responsive phototransistors

Indirect bandgap of multilayer molybdenum disulfide has been recognized as a major hindrance to high responsivity of MoS₂ phototransistors. Here, to overcome this fundamental limitation, we propose a structural engineering of MoS₂ via nano-patterning using block copolymer lithography. The fabricated nanoporous MoS₂, consisting of periodic hexagonal arrays of hexagon nanoholes, includes abundant edges having a zigzag configuration of atomic columns with molybdenum and sulfur atoms. These exposed zigzag edges are responsible for multiple trap states in the bandgap region, as confirmed by photo-excited charge-collection spectroscopy measurements on multilayer nanoporous MoS₂ phototransistors, showing that in-gap states only near the valence band can result in a photogating effect. The effect of nano-patterning is therefore to significantly enhance the responsivity of multilayer nanoporous MoS₂ phototransistors, exhibiting an ultra-high photoresponsivity of 622.2 A W⁻¹. Our nano-patterning of MoS₂ for photosensing application paves a route to structural engineering of two-dimensional materials for highly sensitive and responsive optoelectronic devices.