Defect-Controlled Nucleation and Orientation of WSe 2 on hBN: A Route to Single-Crystal Epitaxial Monolayers

Xiaotian Zhang, Fu Zhang, Yuanxi Wang, Daniel S. Schulman, Tianyi Zhang, Anushka Bansal, Nasim Alem, Saptarshi Das, Vincent H. Crespi, Mauricio Terrones, Joan M. Redwing

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

A defect-controlled approach for the nucleation and epitaxial growth of WSe 2 on hBN is demonstrated. The WSe 2 domains exhibit a preferred orientation of over 95%, leading to a reduced density of inversion domain boundaries (IDBs) upon coalescence. First-principles calculations and experimental studies as a function of growth conditions and substrate pretreatment confirm that WSe 2 nucleation density and orientation are controlled by the hBN surface defect density rather than thermodynamic factors. Detailed transmission electron microscopy analysis provides support for the role of single-atom vacancies on the hBN surface that trap W atoms and break surface symmetry leading to a reduced formation energy for one orientation of WSe 2 domains. Through careful control of nucleation and extended lateral growth time, fully coalesced WSe 2 monolayer films on hBN were achieved. Low-temperature photoluminescence (PL) measurements and transport measurements of back-gated field-effect transistor devices fabricated on WSe 2 /hBN films show improved optical and electrical properties compared to films grown on sapphire under similar conditions. Our results reveal an important nucleation mechanism for the epitaxial growth of van der Waals heterostructures and demonstrate hBN as a superior substrate for single-crystal transition-metal dichalcogenide (TMD) films, resulting in a reduced density of IDBs and improved properties. The results motivate further efforts focused on the development of single crystal hBN substrates and epilayers for synthesis of wafer-scale single crystal TMD films.

Original languageEnglish (US)
Pages (from-to)3341-3352
Number of pages12
JournalACS nano
Volume13
Issue number3
DOIs
StatePublished - Mar 26 2019

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Engineering(all)
  • Physics and Astronomy(all)

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