Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Step engineering for nucleation and domain orientation control in WSe2 epitaxy on c-plane sapphire


Epitaxial growth of two-dimensional transition metal dichalcogenides on sapphire has emerged as a promising route to wafer-scale single-crystal films. Steps on the sapphire act as sites for transition metal dichalcogenide nucleation and can impart a preferred domain orientation, resulting in a substantial reduction in mirror twins. Here we demonstrate control of both the nucleation site and unidirectional growth direction of WSe2 on c-plane sapphire by metal–organic chemical vapour deposition. The unidirectional orientation is found to be intimately tied to growth conditions via changes in the sapphire surface chemistry that control the step edge location of WSe2 nucleation, imparting either a 0° or 60° orientation relative to the underlying sapphire lattice. The results provide insight into the role of surface chemistry on transition metal dichalcogenide nucleation and domain alignment and demonstrate the ability to engineer domain orientation over wafer-scale substrates.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Rent or buy this article

Prices vary by article type



Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Preferred orientation of WSe2 domains.
Fig. 2: Domain nucleation at step edges.
Fig. 3: Competition between the step edge and underlying sapphire symmetry.
Fig. 4: Domain orientation and step edge termination.
Fig. 5: Coalescence of unidirectional WSe2 domains.
Fig. 6: Properties of coalesced WSe2 monolayers.

Data availability

Additional data relevant to the conclusions of this study are available in the Supplementary Information. Growth and characterization data associated with the samples produced in this study are available via ScholarSphere52. This includes substrate preparation and recipe data for samples grown by MOCVD in the 2DCC-MIP facility and standard characterization data including AFM images, room-temperature Raman/photoluminescence spectra and field-emission scanning electron microscopy images of the samples. Videos associated with the DFT results are included as Supplementary Videos 18 and are available via figshare at (ref. 53). Additional datasets related to DFT, SHG, TEM, FET and low-temperature photoluminescence are available from the corresponding author upon request.


  1. Acerce, M., Voiry, D. & Chhowalla, M. Metallic 1 T phase MoS2 nanosheets as supercapacitor electrode materials. Nat. Nanotechnol. 10, 313–318 (2015).

    CAS  Google Scholar 

  2. Late, D. J., Doneux, T. & Bougouma, M. Single-layer MoSe2 based NH3 gas sensor. Appl. Phys. Lett. 105, 3–7 (2014).

    Google Scholar 

  3. Tan, H. et al. Ultrathin 2D photodetectors utilizing chemical vapor deposition grown WS2 with graphene electrodes. ACS Nano 10, 7866–7873 (2016).

    CAS  Google Scholar 

  4. Akinwande, D. et al. Graphene and two-dimensional materials for silicon technology. Nature 573, 507–518 (2019).

    CAS  Google Scholar 

  5. Zhou, H. et al. Large area growth and electrical properties of p-type WSe2 atomic layers. Nano Lett. 15, 709–713 (2015).

    CAS  Google Scholar 

  6. Terrones, H., López-Urías, F. & Terrones, M. Novel hetero-layered materials with tunable direct band gaps by sandwiching different metal disulfides and diselenides. Sci. Rep. 3, 1–8 (2013).

    Google Scholar 

  7. Yuan, H. et al. Zeeman-type spin splitting controlled by an electric field. Nat. Phys. 9, 563–569 (2013).

    CAS  Google Scholar 

  8. Xiao, D. et al. Coupled spin and valley physics in monolayers of MoS2 and other group-VI dichalcogenides. Phys. Rev. Lett. 108, 1–5 (2012).

    Google Scholar 

  9. Fang, H. et al. High-performance single layered WSe2 p-FETs with chemically doped contacts. Nano Lett. 12, 3788–3792 (2012).

    CAS  Google Scholar 

  10. Radisavljevic, B., Radenovic, A., Brivio, J., Giacometti, V. & Kis, A. Single-layer MoS2 transistors. Nat. Nanotechnol. 6, 147–150 (2011).

    CAS  Google Scholar 

  11. Iqbal, M. W. et al. High-mobility and air-stable single-layer WS2 field-effect transistors sandwiched between chemical vapor deposition-grown hexagonal BN films. Sci. Rep. 5, 10699 (2015).

    CAS  Google Scholar 

  12. Chuang, H. J. et al. Highmobility WSe2 p- and n- field-effect transistors contacted by highly doped graphene for low-resistance contacts. Nano Lett. 14, 3594–3601 (2014).

    CAS  Google Scholar 

  13. Choudhury, T. H., Zhang, X., Al Balushi, Z. Y., Chubarov, M. & Redwing, J. M. Epitaxial growth of two-dimensional layered transition metal dichalcogenides. Ann. Rev. Mater. Res. 50, 155–177 (2020).

    CAS  Google Scholar 

  14. Mortelmans, W., De Gendt, S., Heyns, M. & Merckling, C. Epitaxy of 2D chalcogenides: aspects and consequences of weak van der Waals coupling. Appl. Mater. Today 22, 100975 (2021).

    Google Scholar 

  15. Zhang, X. et al. Diffusion-controlled epitaxy of large area coalesced WSe2 monolayers on sapphire. Nano Lett. 18, 1049–1056 (2018).

    CAS  Google Scholar 

  16. Lin, Y. C. et al. Realizing large-scale, electronic-grade two-dimensional semiconductors. ACS Nano 12, 965–975 (2018).

    CAS  Google Scholar 

  17. Mortelmans, W. et al. Peculiar alignment and strain of 2D WSe2 grown by van der Waals epitaxy on reconstructed sapphire surfaces. Nanotechnology 30, 465601 (2019).

    CAS  Google Scholar 

  18. Dong, J., Zhang, L., Dai, X. & Ding, F. The epitaxy of 2D materials growth. Nat. Commun. 11, 5862 (2020).

    CAS  Google Scholar 

  19. Zhou, W. et al. Intrinsic structural defects in monolayer molybdenum disulfide. Nano Lett. 13, 2615–2622 (2013).

    CAS  Google Scholar 

  20. Liu, H. et al. Dense network of one-dimensional midgap metallic modes in monolayer MoSe2 and their spatial undulations. Phys. Rev. Lett. 113, 1–5 (2014).

    CAS  Google Scholar 

  21. Zou, X., Liu, Y. & Yakobson, B. I. Predicting dislocations and grain boundaries in two-dimensional metal-disulfides from the first principles. Nano Lett. 13, 253–258 (2013).

    CAS  Google Scholar 

  22. Du, L. et al. The effect of twin grain boundary tuned by temperature on the electrical transport properties of monolayer MoS2. Crystals 6, 1–9 (2016).

    Google Scholar 

  23. Zhou, S. et al. Atomically sharp interlayer stacking shifts at anti-phase grain boundaries in overlapping MoS2 secondary layers. Nanoscale 10, 16692–16702 (2018).

    CAS  Google Scholar 

  24. Chen, L. et al. Step-edge-guided nucleation and growth of aligned WSe2 on sapphire via a layer-over-layer growth mode. ACS Nano 9, 8368–8375 (2015).

    CAS  Google Scholar 

  25. Chubarov, M. et al. Wafer-scale epitaxial growth of unidirectional WS2 monolayers on sapphire. ACS Nano 15, 2532–2541 (2021).

    CAS  Google Scholar 

  26. Li, T. et al. Epitaxial growth of wafer-scale molybdenum disulfide semiconductor single crystals on sapphire. Nat. Nanotechnol. 16, 1201–1207 (2021).

    CAS  Google Scholar 

  27. Hwang, Y. & Shin, N. Hydrogen assisted step-edge nucleation of MoSe2 monolayers on sapphire substrates. Nanoscale 11, 7701–7709 (2019).

    CAS  Google Scholar 

  28. Suenaga, K. et al. Surface-mediated aligned growth of monolayer MoS2 and in-plane heterostructures with graphene on sapphire. ACS Nano 12, 10032–10044 (2018).

    CAS  Google Scholar 

  29. Cohen, A. et al. Tunsten oxide mediated quasi-van der Waals epitaxy of WS2 on sapphire. ACS Nano 17, 5399–5411 (2023).

    CAS  Google Scholar 

  30. Chubarov, M., Choudhury, T. H., Zhang, X. & Redwing, J. M. In-plane X-ray diffraction for characterization of monolayer and few-layer transition metal dichalcogenide films. Nanotechnology 29, 055706 (2018).

    Google Scholar 

  31. Zheng, P. et al. Universal epitaxy of non-centrosymmetric two-dimensional single-crystal metal dichalcogenides. Nat. Comm. 14, 592 (2023).

    CAS  Google Scholar 

  32. Tsuda, M. et al. Mechanism of H2 pre-annealing on the growth of GaN on sapphire by MOVPE. Appl. Surf. Sci. 216, 585–589 (2003).

    CAS  Google Scholar 

  33. Aljarb, A. et al. Substrate lattice-guided seed formation controls the orientation of 2D transition-metal dichalcogenides. ACS Nano 11, 9215–9222 (2017).

    CAS  Google Scholar 

  34. Wang, Y. et al. P-type electrical contacts for 2D transition-metal dichalcogenides. Nature 610, 61–66 (2022).

    Google Scholar 

  35. Wang, Y. et al. Van der Waals contacts between three-dimensional metals and two-dimensional semiconductors. Nature 568, 70–74 (2019).

    CAS  Google Scholar 

  36. Garcia, A. et al. Analysis of electron beam damage of exfoliated MoS2 sheets and quantitative HAADF-STEM imaging. Ultramicroscopy 146, 33–38 (2014).

    CAS  Google Scholar 

  37. Childres, I. et al. Effect of electron-beam irradiation on graphene field effect devices. Appl. Phys. Lett. 97, 173109 (2010).

    Google Scholar 

  38. Reifsnyder Hickey, D. et al. Illuminating invisible grain boundaries in coalesced single-orientation WS2 monolayer films. Nano Lett. 21, 6487–6495 (2021).

    CAS  Google Scholar 

  39. Huang, P. Y. et al. Grains and grain boundaries in single-layer graphene atomic patchwork quilts. Nature 469, 389–392 (2011).

    CAS  Google Scholar 

  40. Zeng, H., Dai, J., Yao, W., Xiao, D. & Cui, X. Valley polarization in MoS2 monolayers by optical pumping. Nat. Nanotechnol. 7, 490–493 (2012).

    CAS  Google Scholar 

  41. Kim, J. et al. Ultrafast generation of pseudo-magnetic field for valley excitons in WSe2 monolayers. Science 346, 1205–1208 (2014).

    CAS  Google Scholar 

  42. Yan, T., Qiao, X., Tan, P. & Zhang, X. Valley depolarization in monolayer WSe2. Sci. Rep. 5, 15625 (2015).

    CAS  Google Scholar 

  43. Zhu, B., Zeng, H., Dai, J., Gong, Z. & Cui, X. Anomalously robust valley polarization and valley coherence in bilayer WS2. Proc. Natl Acad. Sci. USA 111, 11606 (2014).

    CAS  Google Scholar 

  44. Wang, J. et al. Dual-coupling-guided epitaxial growth of wafer-scale single-crystal WS2 monolayer on vicinal a-plane sapphire. Nat. Nanotechnol. 17, 33–38 (2022).

    CAS  Google Scholar 

  45. Kresse, G. & Furthmüller, J. Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Comput. Mater. Sci. 6, 15–50 (1996).

    CAS  Google Scholar 

  46. Kresse, G. & Furthmüller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 54, 11169–11186 (1996).

    CAS  Google Scholar 

  47. Kresse, G. & Hafner, J. Ab initio molecular dynamics for liquid metals. Phys. Rev. B 47, 558–561 (1993).

    CAS  Google Scholar 

  48. Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865–3868 (1996).

    CAS  Google Scholar 

  49. Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865–3868 (1996); erratum 78, 1396 (1997).

  50. Kresse, G. & Joubert, D. From ultrasoft pseudopotentials to the projector augmented-wave method. Phys. Rev. B 59, 1758–1775 (1999).

    CAS  Google Scholar 

  51. Kresse, G. & Hafner, J. Norm-conserving and ultrasoft pseudopotentials for first-row and transition elements. J. Phys. Condens. Matter 6, 8245–8825 (1994).

    CAS  Google Scholar 

  52. Redwing, J. et al. WSe2 on c-plane sapphire with preferred orientation grown by MOCVD. ScholarSphere (2023).

  53. Nayir, N. & van Duin, A. C. T. Movies showing the nucleation of WSe2 on Al2O3 with mixed (Se/O) and single (Se) steps. figshare (2023).

Download references


The work was financially supported by the National Science Foundation (NSF) through the Pennsylvania State University 2D Crystal Consortium–Materials Innovation Platform (2DCC-MIP) under NSF cooperative agreement numbers DMR-1539916 and DMR-2039351. S.B. and N.A. acknowledge support provided by NSF Career grant number DMR-1654107. T.V.M. and J.M.R. acknowledge support from the Defense Technical Information Center under award number FA9550-21-1-0460. N.T. acknowledges support from the NSF Graduate Research Fellowship Program under grant number DGE1255832. K.Z. and S.H. acknowledge support from NSF under grant numbers ECCS-1943895 and ECCS-2246564 and Air Force Office of Scientific Research under grant number FA9550-22-1-0408. SHG measurements were supported by the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy Office of Science User Facility at Oak Ridge National Laboratory.

Author information

Authors and Affiliations



H.Z. and T.H.C. carried out MOCVD growth, AFM, field-emission scanning electron microscopy and in-plane XRD characterization and data analysis with assistance from K.Y., T.V.M.K., N.T., R.A.M. and S.M.D. N.N., V.H.C. and A.C.T.v.D. carried out DFT calculations. A.B. and B.H. performed in-plane XRD, layer transfer and Raman/photoluminescence characterizations. K.Z. and S.H. performed low-temperature and polarization-resolved photoluminescence measurements. A.A.P. performed SHG characterization. S.B., N.A. and K.W. performed transmission electron microscopy characterizations. A.O. and S.D. fabricated and tested backgated FETs. H.Z., N.N., T.H.C. and J.M.R. co-wrote the manuscript with input from all authors. All authors contributed to the discussions.

Corresponding author

Correspondence to Joan M. Redwing.

Ethics declarations

Competing interests

The authors declare no competing interests.

Peer review

Peer review information

Nature Nanotechnology thanks Wouter Mortelmans and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Figs. 1–26 and Discussion.

Supplementary Video 1

Nucleation of a TRIANGULAR WSe2 on the BOTTOM terrace of a MIXED Se/O step.

Supplementary Video 2

Nucleation of a TRIANGULAR WSe2 on the TOP terrace of a MIXED Se/O step.

Supplementary Video 3

Nucleation of a TRIANGULAR WSe2 on the BOTTOM terrace of a SINGLE Se step.

Supplementary Video 4

Nucleation of a TRIANGULAR WSe2 on the TOP terrace of a SINGLE Se step.

Supplementary Video 5

Nucleation of a RIBBON WSe2 on the BOTTOM terrace of a MIXED Se/O step.

Supplementary Video 6

Nucleation of a RIBBON WSe2 on the TOP terrace of a MIXED Se/O step.

Supplementary Video 7

Nucleation of a RIBBON WSe2 on the BOTTOM terrace of a SINGLE Se step.

Supplementary Video 8

Nucleation of a RIBBON WSe2 on the TOP terrace of a SINGLE Se step.

Rights and permissions

Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Reprints and Permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Zhu, H., Nayir, N., Choudhury, T.H. et al. Step engineering for nucleation and domain orientation control in WSe2 epitaxy on c-plane sapphire. Nat. Nanotechnol. 18, 1295–1302 (2023).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


Quick links

Find nanotechnology articles, nanomaterial data and patents all in one place. Visit Nano by Nature Research