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 (Cu2-xS) was synthesized by chemical vapor deposition, with Cu2-xS nanoparticles vertically stacked on a MoS2 nanosheet. A well-defined epitaxial relationship between MoS2 and Cu2-xS is established, although the corresponding lattice mismatch is as large as 20%. The band-edge alignment is experimentally determined, indicating that the MoS2-Cu2-xS 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 Cu2-xS nanoparticles.