The van der Waals heterostructure of CuPc/MoS2(0001)

Molecular packing and interfacial electronic properties of well-ordered organic semiconductor, copper phthalocyanine, thin films grown on MoS2(0001) are studied with low energy electron diffraction (LEED) optics, atomic force microscope (AFM) and photoelectron spectroscopy (PES). The band structure of MoS2 (0001) around the Gamma point of the surface Brillouin zone is given by angle-resolved photoelectron spectroscopy. The LEED patterns indicate that three equivalent well-ordered two-dimensional square lattices are formed in CuPc monolayer thin film along three surface crystalline axes ([11 (2) over bar0], [1 (2) over bar 10] and [(2) over bar 110]) of MoS2(0001) substrate, respectively. The AFM measurements show that the growth of CuPc on MoS2(0001) occurs in a Stranski-Krastanov mode. The CuPc molecule can be flat-laying on MoS2 (0001) at low coverage (similar to 0.3 nm), but form strip-like crystals along the surface crystal axes of MoS2(0001) at high coverage (> 2.4 nm). The CuPc molecule shows obvious anisotropy, indicating that the molecular plane is not parallel to the MoS2 surface. The PES measurements show there is no charge transfer process at the interface, indicating weak van der Waals interaction between CuPc and MoS2 (0001).