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Effect of calcium deposition on the surfaces of WSe2 and WS2

N. Ghasemi1, L. Karbivska1,2, T. Klaproth1, M. Knupfer1, B. Büchner1,3, and A. Koitzsch1

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Phys. Rev. Materials 10, 084004 – Published 24 August, 2026

DOI: https://doi.org/10.1103/s91z-v9m2

Abstract

Functionalization of 2D materials and of transition metal dichalcogenides (TMDs) in particular is central for next generation devices and other applications. Here we study the effect of calcium dosing on the surfaces of clean WSe2 and WS2 in ultrahigh vacuum by x-ray photoelectron spectroscopy, low energy electron diffraction, and scanning electron microscopy. We find that Ca reacts with the chalcogens to CaSex or CaSx and reduces the remaining tungsten. Ca forms an overlayer on top and causes an outdiffusion of the chalcogen. The overlayer oxidizes easily. We obtained detailed understanding of the interactions of archetypal TMD with an abundant alkali-earth element, which expands our knowledge of metal-surface interactions and of surface manipulation of 2D materials.

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References (20)

  1. S. Manzeli, D. Ovchinnikov, D. Pasquier, O. V. Yazyev, and A. Kis, 2D transition metal dichalcogenides, Nat. Rev. Mater. 2, 17033 (2017).
  2. Z. Hu, Z. Wu, C. Han, J. He, Z. Ni, and W. Chen, Two-dimensional transition metal dichalcogenides: Interface and defect engineering, Chem. Soc. Rev. 47, 3100 (2018).
  3. J. M. Riley, W. Meevasana, L. Bawden, M. Asakawa, T. Takayama, T. Eknapakul, T. K. Kim, M. Hoesch, S.-K. Mo, H. Takagi, T. Sasagawa, M. S. Bahramy, and P. D. C. King, Negative electronic compressibility and tunable spin splitting in WSe2, Nat. Nanotechnol. 10, 1043 (2015).
  4. Y. Zhang, M. M. Ugeda, C. Jin, S.-F. Shi, A. J. Bradley, A. Martin-Recio, H. Ryu, J. Kim, S. Tang, Y. Kim, B. Zhou, C. Hwang, Y. Chen, F. Wang, M. F. Crommie, Z. Hussain, Z.-X. Shen, and S.-K. Mo, Electronic structure, surface doping, and optical response in epitaxial WSe2 thin films, Nano Lett. 16, 2485 (2016).
  5. M. Kang, B. Kim, S. H. Ryu, S. W. Jung, J. Kim, L. Moreschini, C. Jozwiak, E. Rotenberg, A. Bostwick, and K. S. Kim, Universal mechanism of band-gap engineering in transition-metal dichalcogenides, Nano Lett. 17, 1610 (2017).
  6. W. Liu, J. Kang, D. Sarkar, Y. Khatami, D. Jena, and K. Banerjee, Role of metal contacts in designing high-performance monolayer n-type WSe2 field effect transistors, Nano Lett. 13, 1983 (2013).
  7. D.-H. Kang, J. Shim, S. K. Jang, J. Jeon, M. H. Jeon, G. Y. Yeom, W.-S. Jung, Y. H. Jang, S. Lee, and J.-H. Park, Controllable nondegenerate p-type doping of tungsten diselenide by octadecyltrichlorosilane, ACS Nano 9, 1099 (2015).
  8. F. Rückerl, T. Klaproth, R. Schuster, B. Büchner, and M. Knupfer, Surface functionalization of WSe2 by F16CoPc, Phys. Status Solidi B 254, 1600656 (2017).
  9. F. S. Ohuchi, W. Jaegermann, C. Pettenkofer, and B. A. Parkinson, Semiconductor to metal transition of WS2 induced by K intercalation in ultrahigh vacuum, Langmuir 5, 439 (1989).
  10. M. Ahmad, E. Müller, C. Habenicht, R. Schuster, M. Knupfer, and B. Büchner, Semiconductor-to-metal transition in the bulk of WSe2 upon potassium intercalation, J. Phys.: Condens. Matter 29, 165502 (2017).
  11. R. B. Somoano, V. Hadek, and A. Rembaum, Alkali metal intercalates of molybdenum disulfide, J. Chem. Phys. 58, 697 (1973).
  12. S. McDonnell, R. Addou, C. Buie, R. M. Wallace, and C. L. Hinkle, Defect-dominated doping and contact resistance in MoS2, ACS Nano 8, 2880 (2014).
  13. C. M. Smyth, R. Addou, S. McDonnell, C. L. Hinkle, and R. M. Wallace, WSe2-contact metal interface chemistry and band alignment under high vacuum and ultra high vacuum deposition conditions, 2D Mater. 4, 025084 (2017).
  14. C. M. Smyth, L. A. Walsh, P. Bolshakov, M. Catalano, M. Schmidt, B. Sheehan, R. Addou, L. Wang, J. Kim, M. J. Kim, C. D. Young, C. L. Hinkle, and R. M. Wallace, Engineering the interface chemistry for scandium electron contacts in WSe2 transistors and diodes, 2D Mater. 6, 045020 (2019).
  15. K. Koepernik and H. Eschrig, Full-potential nonorthogonal local-orbital minimum-basis band-structure scheme, Phys. Rev. B 59, 1743 (1999).
  16. J. P. Perdew and Y. Wang, Accurate and simple analytic representation of the electron-gas correlation energy, Phys. Rev. B 45, 13244 (1992).
  17. M. D. Slater, D. Kim, E. Lee, and C. S. Johnson, Sodium-ion batteries, Adv. Funct. Mater. 23, 947 (2013).
  18. W. Luo, J. Wan, B. Ozdemir, W. Bao, Y. Chen, J. Dai, H. Lin, Y. Xu, F. Gu, V. Barone, and L. Hu, Potassium ion batteries with graphitic materials, Nano Lett. 15, 7671 (2015).
  19. S. Das, H.-Y. Chen, A. V. Penumatcha, and J. Appenzeller, High performance multilayer MoS2 transistors with scandium contacts, Nano Lett. 13, 100 (2013).
  20. L. Li, M. Engel, D. B. Farmer, S.-j. Han, and H.-S. P. Wong, High-performance p-type black phosphorus transistor with scandium contact, ACS Nano 10, 4672 (2016).

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Phys. Rev. Materials 10, 084004– Published 24 August, 2026
  • Received 3 February 2026
  • Accepted 2 June 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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