Nano Research

, Volume 11, Issue 3, pp 1676–1686 | Cite as

Van der Waals interfacial bonding and intermixing in GeTe-Sb2Te3-based superlattices

  • Andriy LotnykEmail author
  • Isom Hilmi
  • Ulrich Ross
  • Bernd Rauschenbach
Research Article


Interfacial phase change memory (iPCM) based on GeTe and Sb2Te3 superlattices (SLs) is an emerging contender for non-volatile data storage applications. A detailed knowledge of the atomic structure of these materials is crucial for further development of SLs and for a better understanding of the resistivity switching characteristics of iPCM devices. In this work, crystalline GeTe-Sb2Te3-based SLs, produced by pulsed laser deposition onto a Si(111) substrate at temperatures lower than in previous studies, are analyzed by advanced scanning transmission electron microscopy. The results reveal the formation of Ge-rich Ge(x+y)Sb(2–y)Tez building blocks with specific numbers of ordered Ge cation layers (between 1 and 5) and disordered cation layers (4) for z = 6–10, as well as intermixed cation layers for z = 5, within the SLs. The G Ge(x+y)Sb(2–y)Tez units are separated from the Sb2Te3 building blocks by van der Waals gaps. In particular, the interlayer bonding is promoted by the formation of outermost cation layers consisting of intermixed GeSb within the building blocks adjacent to the van der Waals gaps. The Ge(x+y)Sb(2–y)Tez units with z > 5 retain metastable crystal structures with two-dimensional bonding within the SLs. The present study shed new light on the possible configurations of the building units that can be formed during the synthesis of GeTe-Sb2Te3-based iPCM materials. In addition, a possible switching mechanism active in iPCM materials is discussed.


interfacial phase change memory (iPCM) thin films intermixing Cs-corrected scanning transmission electron microscopy 


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We would like to thank Mrs. A. Mill for her assistance in the TEM specimen preparation by FIB. The financial support of the European Union and the Free State of Saxony (LenA project; project No. 100074065) is greatly acknowledged.

Supplementary material

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van der Waals interfacial bonding and intermixing in GeTe-Sb2Te3-based superlattices


  1. [1]
    Feinleib, J.; Deneufville, J.; Moss, S. C.; Ovshinsky, S. R. Rapid reversible light-induced crystallization of amorphous semiconductors. Appl. Phys. Lett. 1971, 18, 254–257.CrossRefGoogle Scholar
  2. [2]
    Wuttig, M.; Yamada, N. Phase-change materials for rewriteable data storage. Nat. Mater. 2007, 6, 824–832.CrossRefGoogle Scholar
  3. [3]
    Simpson, R. E.; Fons, P.; Kolobov, A. V.; Fukaya, T.; Krbal, M.; Yagi, T.; Tominaga, J. Interfacial phase-change memory. Nat. Nanotechnol. 2011, 6, 501–505.CrossRefGoogle Scholar
  4. [4]
    Momand, J.; Wang, R. N.; Boschker, J. E.; Verheijen, M. A.; Calarco, R.; Kooi, B. J. Interface formation of two- and three-dimensionally bonded materials in the case of GeTe-Sb2Te3 superlattices. Nanoscale 2015, 7, 19136–19143.CrossRefGoogle Scholar
  5. [5]
    Wang, R. N.; Bragaglia, V.; Boschker, J. E.; Calarco, R. Intermixing during epitaxial growth of van der Waals bonded nominal GeTe/Sb2Te3 superlattices. Cryst. Growth Des. 2016, 16, 3596–3601.CrossRefGoogle Scholar
  6. [6]
    Casarin, B.; Caretta, A.; Momand, J.; Kooi, B. J.; Verheijen, M. A.; Bragaglia, V.; Calarco, R.; Chukalina, M.; Yu, X. M.; Robertson, J. et al. Revisiting the local structure in Ge-Sb-Te based chalcogenide superlattices. Sci. Rep. 2016, 6, 22353.CrossRefGoogle Scholar
  7. [7]
    Momand, J.; Lange, F. R. L.; Wang, R. N.; Boschker, J. E.; Verheijen, M. A.; Calarco, R.; Wuttig, M.; Kooi, B. J. Atomic stacking and van-der-Waals bonding in GeTe-Sb2Te3 superlattices. J. Mater. Res. 2016, 31, 3115–3124.CrossRefGoogle Scholar
  8. [8]
    Lotnyk, A.; Ross, U.; Bernütz, S.; Thelander, E.; Rauschenbach, B. Local atomic arrangements and lattice distortions in layered Ge-Sb-Te crystal structures. Sci. Rep. 2016, 6, 26724.CrossRefGoogle Scholar
  9. [9]
    Tominaga, J.; Kolobov, A. V.; Fons, P.; Nakano, T.; Murakami, S. Ferroelectric order control of the dirac-semimetal phase in GeTe-Sb2Te3 superlattices. Adv. Mater. Interfaces 2014, 1, 1300027.CrossRefGoogle Scholar
  10. [10]
    Tominaga, J.; Kolobov, A. V.; Fons, P. J.; Wang, X. M.; Saito, Y.; Nakano, T.; Hase, M.; Murakami, S.; Herfort, J.; Takagaki, Y. Giant multiferroic effects in topological GeTe-Sb2Te3 superlattices. Sci. Technol. Adv. Mater. 2015, 16, 014402.CrossRefGoogle Scholar
  11. [11]
    Ohyanagi, T.; Kitamura, M.; Araidai, M.; Kato, S.; Takaura, N.; Shiraishi, K. GeTe sequences in superlattice phase change memories and their electrical characteristics. Appl. Phys. Lett. 2014, 104, 252106.CrossRefGoogle Scholar
  12. [12]
    Yu, X. M.; Robertson, J. Modeling of switching mechanism in GeSbTe chalcogenide superlattices. Sci. Rep. 2015, 5, 12612.CrossRefGoogle Scholar
  13. [13]
    Yu, X. M.; Robertson, J. Atomic layering, intermixing and switching mechanism in Ge-Sb-Te based chalcogenide superlattices. Sci. Rep. 2016, 6, 37325.CrossRefGoogle Scholar
  14. [14]
    Kalikka, J.; Zhou, X. L.; Behera, J.; Nannicini, G.; Simpson, R. E. Evolutionary design of interfacial phase change van der Waals heterostructures. Nanoscale 2016, 8, 18212–18220.CrossRefGoogle Scholar
  15. [15]
    Lotnyk, A.; Poppitz, D.; Ross, U.; Gerlach, J. W.; Frost, F.; Bernuütz, S.; Thelander, E.; Rauschenbach, B. Focused highand low-energy ion milling for TEM specimen preparation. Microelectroni. Reliab. 2015, 55, 2119–2125.CrossRefGoogle Scholar
  16. [16]
    Barthel, J. Probe-STEM simulation software[Online]. http:// Scholar
  17. [17]
    Schneider, M. N.; Oeckler, O. Unusual solid solutions in the system Ge-Sb-Te: The crystal structure of 33RGe4-xSb2-yTe7(x, y ˜ 0.1) is Isostructural to that of Ge3Sb2Te6. Z. Anorg. Allg. Chem. 2008, 634, 2557–2561.CrossRefGoogle Scholar
  18. [18]
    Urban, P.; Schneider, M. N.; Erra, L.; Welzmiller, S.; Fahrnbauer, F.; Oeckler, O. Temperature dependent resonant X-ray diffraction of single-crystalline Ge2Sb2Te5. CrystEngComm 2013, 15, 4823–4829.CrossRefGoogle Scholar
  19. [19]
    Kokh, K. A.; Atuchin, V. V.; Gavrilova, T. A.; Kuratieva, N. V.; Pervukhina, N. V.; Surovtsev, N. V. Microstructural and vibrational properties of PVT grown Sb2Te3 crystals. Solid State Commun. 2014, 177, 16–19.CrossRefGoogle Scholar
  20. [20]
    Bauer Pereira, P.; Sergueev, I.; Gorsse, S.; Dadda, J.; Müller, E.; Hermann, R. P. Lattice dynamics and structure of GeTe, SnTe and PbTe. Phys. Status Solidi B 2013, 250, 1300–1307.CrossRefGoogle Scholar
  21. [21]
    Ross, U.; Lotnyk, A.; Thelander, E.; Rauschenbach, B. Direct imaging of crystal structure and defects in metastable Ge2Sb2Te5 by quantitative aberration-corrected scanning transmission electron microscopy. Appl. Phys. Lett. 2014, 104, 121904.CrossRefGoogle Scholar
  22. [22]
    Lotnyk, A.; Bernütz, S.; Sun, X. X.; Ross, U.; Ehrhardt, M.; Rauschenbach, B. Real-space imaging of atomic arrangement and vacancy layers ordering in laser crystallised Ge2Sb2Te5 phase change thin films. Acta Mater. 2016, 105, 1–8.CrossRefGoogle Scholar
  23. [23]
    Mio, A. M.; Privitera, M. S.; Bragaglia, V.; Arciprete, F.; Bongiorno, C.; Calarco, R.; Rimini, E. Chemical and structural arrangement of the trigonal phase in GeSbTe thin films. Nanotechnology 2017, 28, 065706.CrossRefGoogle Scholar
  24. [24]
    Hilmi, I.; Lotnyk, A.; Gerlach, J. W.; Schumacher, P.; Rauschenbach, B. Epitaxial formation of cubic and trigonal Ge-Sb-Te thin films with heterogeneous vacancy structures. Mater. Des. 2017, 115, 138–146.CrossRefGoogle Scholar
  25. [25]
    Hartel, P.; Rose, H.; Dinges, C. Conditions and reasons for incoherent imaging in STEM. Ultramicroscopy 1996, 63, 93–114.CrossRefGoogle Scholar
  26. [26]
    Rafferty, B.; Nellist, D.; Pennycook, J. On the origin of transverse incoherence in Z-contrast STEM. J. Electron Microsc. 2001, 50, 227–233.Google Scholar
  27. [27]
    Wang, Z. W.; Li, Z. Y.; Park, S. J.; Abdela, A.; Tang, D.; Palmer, R. E. Quantitative Z-contrast imaging in the scanning transmission electron microscope with size-selected clusters. Phys. Rev. B 2011, 84, 073408.CrossRefGoogle Scholar
  28. [28]
    Kim, S.; Jung, Y.; Kim, J. J.; Lee, S.; Lee, H. Z-contrast dependence of quantitative scanning transmission electron microscopy image of Si1-xGex binary crystals. J. Alloys Compd. 2015, 618, 545–550.Google Scholar
  29. [29]
    Ross, U.; Lotnyk, A.; Thelander, E.; Rauschenbach, B. Microstructure evolution in pulsed laser deposited epitaxial Ge-Sb-Te chalcogenide thin films. J. Alloys Compd. 2016, 676, 582–590.CrossRefGoogle Scholar
  30. [30]
    Hurych, Z.; Benbow R. L. Photoemission studies of interface properties of thin Bi overlayers on two-dimensional crystals of BixSb2-xTe3 semiconductors using synchrotron radiation. Phys. Rev. B 1977, 16, 3707–3712.CrossRefGoogle Scholar
  31. [31]
    Wagner, V.; Doling, G.; Powell, B.M.; Landweher, G. Lattice vibrations of Bi2Te3. Phys. Status Solidi B 1978, 85, 311–317.CrossRefGoogle Scholar
  32. [32]
    Sa, B. S.; Miao, N. H.; Zhou, J.; Sun, Z. M.; Ahuja, R. Ab initio study of the structure and chemical bonding of stable Ge3Sb2Te6. Phys. Chem. Chem. Phy. 2010, 12, 1585–1588.CrossRefGoogle Scholar
  33. [33]
    Matsunaga, T.; Kojima, R.; Yamada, N.; Kifune, K.; Kubota, Y.; Takata, M. Structural investigation of Ge3Sb2Te6, an intermetallic compound in the GeTe-Sb2Te3 homologous series. Appl. Phys. Lett. 2007, 90, 161919.CrossRefGoogle Scholar
  34. [34]
    Matsunaga, T.; Yamada, N.; Kubota, Y. Structures of stable and metastable Ge2Sb2Te5, an intermetallic compound in GeTe-Sb2Te3 pseudobinary systems. Acta Cryst. B 2004, 60, 685–691.CrossRefGoogle Scholar
  35. [35]
    Da Silva, J. L. F.; Walsh, A.; Lee, H. Insights into the structure of the stable and metastable (GeTe)m(Sb2Te3)m compounds. Phys. Rev. B 2008, 78, 224111.CrossRefGoogle Scholar
  36. [36]
    Gorbenko, O. Y.; Samoilenkov, S. V.; Graboy, I. E.; Kaul, A. R. Epitaxial stabilization of oxides in thin films. Chem. Mat. 2002, 14, 4026–4043.CrossRefGoogle Scholar
  37. [37]
    Lotnyk, A.; Senz, S.; Hesse, D. Orientation relationships of SrTiO3 and MgTiO3 thin films grown by vapor-solid reactions on (100) and (110) TiO2(rutile) single crystals. J. Phys. Chem. C 2007, 111, 6372–6379.CrossRefGoogle Scholar
  38. [38]
    Lee, S.; Ivanov, I. N.; Keum, J. K.; Lee, H. N. Epitaxial stabilization and phase instability of VO2 polymorphs. Sci. Rep. 2016, 6, 19621.CrossRefGoogle Scholar
  39. [39]
    Gaspard, J. P.; Ceolin, R. Hume-rothery rule in V-VI compounds. Solid State Commun. 1992, 84, 839–842.CrossRefGoogle Scholar
  40. [40]
    Gaspard, J. P. Structure of covalently bonded materials: From the peierls distortion to phase-change materials. C. R. Phys. 2016, 17, 389–405.CrossRefGoogle Scholar

Copyright information

© Tsinghua University Press and Springer-Verlag GmbH Germany 2018

Authors and Affiliations

  • Andriy Lotnyk
    • 1
    Email author
  • Isom Hilmi
    • 1
  • Ulrich Ross
    • 1
  • Bernd Rauschenbach
    • 1
  1. 1.Leibniz Institute of Surface Modification (IOM)LeipzigGermany

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