Epitaxial Synthesis of Monolayer PtSe2 Single Crystal on MoSe2 with Strong Interlayer Coupling.

Abstract

PtSe2, a new layered two-dimensional material, has drawn intensive attention owing to its layer-dependent band structure, high air stability and spin-layer locking effect which embraces the applications for next-generation optoelectronic, electronic devices and catalysis. However, synthesis of large monolayer PtSe2 single crystal is challenging due to the low chemical reactivity of Pt sources. Here, we report the synthesis of monolayer PtSe2 single crystal via epitaxy growth on MoSe2 by a one-step chemical vapor deposition (CVD) method. The underlying MoSe2 substrate plays a key role for the monolayer growth of PtSe2. The periodic Moiré patterns from the vertically stacked heterostructure (PtSe2/MoSe2) are clearly identified via annular dark-field scanning transition electron microscopy (ADF-STEM). First-principles calculations show a type-II band alignment and reveal interface states originating from the Strong-Weak Interlayer Coupling (S-WIC) between PtSe2 and MoSe2 monolayers, as demonstrated by the electrostatic force microscopy (EFM) observed edge states. Ultrafast transient dynamics of photoexcited carrier in PtSe2/MoSe2 heterostructure show ultrafast hole transfer between PtSe2 and MoSe2 monolayers, which matches well with the theoretical results. Our study opens a new way to synthesize uniform PtSe2 monolayers and other Pt-based heterostructures. These results also shed considerable lights on optoelectronics in vdW solids consisting of weak and strong interlayer coupled materials.