Phase Variations and Layer Epitaxy of 2D PdSe2Grown on 2D Monolayers by Direct Selenization of Molecular Pd Precursors

Kuo Lun Tai, Jun Chen, Yi Wen, Hyoju Park, Qianyang Zhang, Yang Lu, Ren Jie Chang, Peng Tang, Christopher S. Allen, Wen-Wei Wu*, Jamie H. Warner

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Two-dimensional (2D) materials and van der Waals heterostructures with atomic-scale thickness provide enormous potential for advanced science and technology. However, insufficient knowledge of compatible synthesis impedes wafer-scale production. PdSe2 and Pd2Se3 are two of the noble transition-metal chalcogenides with excellent physical properties that have recently emerged as promising materials for electronics, optoelectronics, catalyst, and sensors. This research presents a feasible approach to synthesize PdSe2 and Pd2Se3 with inherently asymmetric structure on honeycomb lattice 2D monolayer substrates of graphene and MoS2. We directly deposit a molecular transition-metal precursor complex on the surface of the 2D substrates, followed by low-temperature selenization by chemical vapor flow. Parameter control leads to tuning of the material from monolayer nanocrystals with Pd2Se3 phase, to continuous few-layer PdSe2 films. Annular dark-field scanning transmission electron microscopy (ADF-STEM) reveals the structure, phase variations, and heteroepitaxy at the atomic level. PdSe2 with unconventional interlayer stacking shifts appeared as the kinetic product, whereas the bilayer PdSe2 and monolayer Pd2Se3 are the thermodynamic product. The epitaxial alignment of interlayer rotation and translation between the PdSe2 and underlying 2D substrate was also revealed by ADF-STEM. These results offer both nanoscale and atomic-level insights into direct growth of van der Waals heterostructures, as well as an innovative method for 2D synthesis by predetermined nucleation.

Original languageEnglish
JournalACS Nano
StateAccepted/In press - 2020


  • 2D materials
  • graphene
  • MoS
  • PdSe
  • TEM

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