Vertical Stacking of Copper Sulfide Nanoparticles and Molybdenum Sulfide Nanosheets for Enhanced Nonlinear Absorption

The construction of p-n junctions is necessitated by applications which require effective charge separation. Here, a novel heterostructure (HS) of molybdenum sulfide (MoS₂) and copper sulfide (Cu_2-S) was synthesized by chemical vapor deposition, with Cu_2-S nanoparticles vertically stacked on a MoS₂ nanosheet. A well-defined epitaxial relationship between MoS₂ and Cu_2-S is established, although the corresponding lattice mismatch is as large as 20%. The band-edge alignment is experimentally determined, indicating that the MoS₂-Cu_2-S HS is a type II heterojunction. Photoluminescence quenching indicates effective charge separation in HS. The resultant HS shows enhanced nonlinear absorption in comparison with single-component MoS₂ nanosheets and Cu_2-S nanoparticles.