Epitaxial synthesis and electronic properties of monolayer Pd₂Se₃

Two-dimensional (2D) materials received large amount of studies because of the enormous potential in basic science and industrial applications. Monolayer Pd₂Se₃ is a fascinating 2D material that was predicted to possess excellent thermoelectric, electronic, transport, and optical properties. However, the fabrication of large-scale and high-quality monolayer Pd₂Se₃ is still challenging. Here, we report the synthesis of large-scale and high-quality monolayer Pd₂Se₃ on graphene-SiC (0001) by a two-step epitaxial growth. The atomic structure of Pd₂Se₃ was investigated by scanning tunneling microscope (STM) and confirmed by non-contact atomic force microscope (nc-AFM). Two subgroups of Se atoms have been identified by nc-AFM image in agreement with the theoretically predicted atomic structure. Scanning tunneling spectroscopy (STS) reveals a bandgap of 1.2 eV, suggesting that monolayer Pd₂Se₃ can be a candidate for photoelectronic applications. The atomic structure and defect levels of a single Se vacancy were also investigated. The spatial distribution of STS near the Se vacancy reveals a highly anisotropic electronic behavior. The two-step epitaxial synthesis and characterization of Pd₂Se₃ provide a promising platform for future investigations and applications.