English

Periodic Misfit Dislocation and Electron Aggregation at (010) PbTiO₃/SrTiO₃ Heterointerface

• Chen Xing ,
• Tian He ^, ,
• Zhang Ze

• State Key Laboratory of Silicon Materials, Center of Electron Microscopy, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China

Corresponding author: He Tian. Email: hetian@zju.edu.cn

• Received Date: 04 June 2019
  Accepted Date: 28 June 2019
  Revised Date: 27 June 2019
  Available Online: 15 November 2020
• Fund Project:

  The project was supported by the National Key Basic Research Development Program of China (973) (2015CB654900)

Abstract: It is important to determine the effects of misfit dislocations and other defects on the domain structure, ferroelectricity, conductivity, and other physical properties of ferroelectric thin films to understand their ferroelectric and piezoelectric behaviors. Much attention has been given to ferroelectric PbTiO₃/SrTiO₃ or PbZr_0.2Ti_0.8O₃/SrTiO₃ heterointerfaces, at which improper ferroelectricity, a spin-polarized two-dimensional electron gas, and other physical phenomena have been found. However, those heterointerfaces were all (001) planes, and there has been no experimental studies on the growth of (010) PbTiO₃/SrTiO₃ heterointerface due to the 6.4% misfit between two materials. In this study, we selected an atomically flat (010) PbTiO₃/SrTiO₃ heterointerface grown using a two-step hydrothermal method as the research subject, and this is the first experimental report on that interface. Interfacial dislocations can play a significant role in causing dramatic changes in the Curie temperature and polarization distribution near the dislocation cores, especially when the size of a ferroelectric thin film is scaled down to the nanoscale. The results of previous studies on the effects of interfacial dislocations on the physical properties of ferroelectric thin films have been contradictory. Thus, this issue needs to be explored more deeply in the future. This study used aberration corrected scanning transmission electron microscopy (STEM) to study the atomic structure of a (010) PbTiO₃/SrTiO₃ heterointerface and found periodic misfit dislocations with a Burgers vector of a[001]. The extra planes at the dislocation cores could relieve the misfit strain between the two materials in the [001] direction and thus allowed the growth of such an atomically sharp heterointerface. Moreover, monochromated electron energy-loss spectroscopy with an atomic scale spatial resolution and high energy resolution was used to explore the charge distribution near the periodic misfit dislocation cores. The fine structure of the Ti L edge was quantitatively analyzed by linearly fitting the experimental spectra recorded at various locations near and at the misfit dislocation cores with the Ti³⁺ and Ti⁴⁺ reference spectra. Therefore, the accurate valence change of Ti could be determined, which corresponded to the charge distribution. The probable existence of an aggregation of electrons was found near the a[001] dislocation cores, and the density of the electrons calculated from the valence change was 0.26 electrons per unit cell. Based on an analysis of the fine structure of the oxygen K edge, it could be argued that the electrons aggregating at the dislocation cores came from the oxygen vacancies in the interior regions of the PbTiO₃. This aggregation of electrons will probably increase the electron conductivity along the dislocation line. The physics of two-dimensional charge distributions at oxide interfaces have been intensively studied, however, little attention had been given to the one-dimensional charge distribution. Therefore, the results of this study can stimulate research interest in exploring the influence of the interfacial dislocations on the physics of ferroelectric heterointerfaces.

Key words:
• PbTiO₃
•  /  SrTiO₃
•  /  Heterointerface
•  /  Misfit dislocation
•  /  Aberration corrected transmission electron microscopy
•  /  Electron energy-loss spectroscopy

• 1. [1]

     Ohtomo, A.; Muller, D.; Grazul, J.; Hwang, H. Y. Nature 2002, 419, 378. doi: 10.1038/nature00977

  2. [2]

     Ohtomo, A.; Hwang, H. Y. Nature 2004, 427, 423. doi: 10.1038/nature02308

  3. [3]

     Reyren, N.; Thiel, S.; Caviglia, A. D.; Kourkoutis, L. F.; Hammerl, G.; Richter, C.; Schneider, C. W.; Kopp, T.; Ruetschi, A. S.; Jaccard, D.; et al. Science 2007, 317, 1196. doi: 10.1126/science.1146006

  4. [4]

     Brinkman, A.; Huijben, M.; Van Zalk, M.; Huijben, J.; Zeitler, U.; Maan, J. C.; Van der Wiel, W. G.; Rijnders, G.; Blank, D. H. A.; Hilgenkamp, H. Nat. Mater. 2007, 6, 493. doi: 10.1038/nmat1931

  5. [5]

     Bousquet, E.; Dawber, M.; Stucki, N.; Lichtensteiger, C.; Hermet, P.; Gariglio, S.; Triscone, J. M.; Ghosez, P. Nature 2008, 452, 732. doi: 10.1038/nature06817

  6. [6]

     Zubko, P.; Stucki, N.; Lichtensteiger, C.; Triscone, J. M. Phys. Rev. Lett. 2010, 104, 187601. doi: 10.1103/PhysRevLett.104.187601

  7. [7]

     Zhang, Y.; Xie, L.; Kim, J.; Stern, A.; Wang, H.; Zhang, K.; Yan, X.; Li, L.; Liu, H.; Zhao, G.; et al. Nat. Commun. 2018, 9, 685. doi: 10.1038/s41467-018-02914-9

  8. [8]

     Zheng, Y.; Wang, B.; Woo, C. H. J. Mech. Phys. Solids 2007, 55, 1661. doi: 10.1016/j.jmps.2007.01.011

  9. [9]

     Zheng, Y.; Wang, B.; Woo, C. H. Appl. Phys. Lett. 2006, 88, 3. doi: 10.1063/1.2177365

  10. [10]

      Alpay, S. P.; Misirlioglu, I. B.; Nagarajan, V.; Ramesh, R. Appl. Phys. Lett. 2004, 85, 2044. doi: 10.1063/1.1788894

  11. [11]

      Jia, C. L.; Mi, S. B.; Urban, K.; Vrejoiu, I.; Alexe, M.; Hesse, D. Phys. Rev. Lett. 2009, 102, 4. doi: 10.1103/PhysRevLett.102.117601

  12. [12]

      Chu, M. W.; Szafraniak, I.; Scholz, R.; Harnagea, C.; Hesse, D.; Alexe, M.; Gösele, U. Nat. Mater. 2004, 3, 87. doi: 10.1038/nmat1057

  13. [13]

      Wu, H. H.; Wang, J.; Cao, S. G.; Zhang, T. Y. Appl. Phys. Lett. 2013, 102, 232904. doi: 10.1063/1.4809945.

  14. [14]

      黄威, 邬春阳, 曾跃武, 金传洪, 张泽.物理化学学报, 2016, 32, 2287. doi: 10.3866/PKU.WHXB201605164Huang, W.; Wu, C. Y.; Zeng, Y. W.; Jin, C. H.; Zhang, Z. Acta Phys. -Chim. Sin. 2016, 32, 2287. doi: 10.3866/PKU.WHXB201605164

  15. [15]

      吕丹辉, 朱丹诚, 金传洪.物理化学学报, 2017, 33, 1514. doi: 10.3866/PKU.WHXB201705123Lu, D. H.; Zhu, D. C.; Jin, C. H. Acta Phys. -Chim. Sin. 2017, 33, 1514. doi: 10.3866/PKU.WHXB201705123

  16. [16]

      Chang, C. P.; Chu, M. W.; Jeng, H. T.; Cheng, S. L.; Lin, J. G.; Yang, J. R.; Chen, C. H. Nat. Commun. 2014, 5, 8. doi: 10.1038/ncomms4522

  17. [17]

      Chao, C.; Ren, Z.; Zhu, Y.; Xiao, Z.; Liu, Z.; Xu, G.; Mai, J.; Li, X.; Shen, G.; Han, G. Angew. Chem. Int. Ed. 2012, 51, 9283. doi: 10.1002/anie.201204792

  18. [18]

      Ren, Z. H.; Wu, M. J.; Chen, X.; Li, W.; Li, M.; Wang, F.; Tian, H.; Chen, J. Z.; Xie, Y. W.; Mai, J. Q.; et al. Adv. Mater. 2018, 30, 1707017. doi: 10.1002/adma.201707017

  19. [19]

      Verbeeck, J.; Van Aert, S. Ultramicroscopy 2004, 101, 207. doi: 10.1016/j.ultramic.2004.06.004

  20. [20]

      Verbeeck, J.; Van Aert, S.; Bertoni, G. Ultramicroscopy 2006, 106, 976. doi: 10.1016/j.ultramic.2006.05.006

  21. [21]

      Verbeeck, J.; Bertoni, G. Microchim. Acta 2008, 161, 439. doi: 10.1007/s00604-008-0948-7

  22. [22]

      Leapman, R.; Grunes, L. Phys. Rev. Lett. 1980, 45, 397. doi: 10.1103/PhysRevLett.45.397

  23. [23]

      Muller, D. A.; Nakagawa, N.; Ohtomo, A.; Grazul, J. L.; Hwang, H. Y. Nature 2004, 430, 657. doi: 10.1038/nature02756

  24. [24]

      Kalabukhov, A.; Gunnarsson, R.; Börjesson, J.; Olsson, E.; Claeson, T.; Winkler, D. Phys. Rev. B 2007, 75, 121404. doi: 10.1103/PhysRevB.75.121404

  25. [25]

      Siemons, W.; Koster, G.; Yamamoto, H.; Harrison, W. A.; Lucovsky, G.; Geballe, T. H.; Blank, D. H.; Beasley, M. R. Phys. Rev. Lett. 2007, 98, 196802. doi: 10.1103/PhysRevLett.98.196802

  26. [26]

      Basletic, M.; Maurice, J. -L.; Carrétéro, C.; Herranz, G.; Copie, O.; Bibes, M.; Jacquet, É.; Bouzehouane, K.; Fusil, S.; Barthélémy, A. Nat. Mater. 2008, 7, 621. doi: 10.1038/nmat2223

  27. [27]

      Ryu, J.; Han, G.; Song, T. K.; Welsh, A.; Trolier-McKinstry, S.; Choi, H.; Lee, J. P.; Kim, J. W.; Yoon, W. H.; Choi, J. J.; et al. ACS Appl. Mater. Inter. 2014, 6, 11980. doi: 10.1021/am5000307

  28. [28]

      Kiguchi, T.; Aoyagi, K.; Ehara, Y.; Funakubo, H.; Yamada, T.; Usami, N.; Konno, T. J. Sci. Technol. Adv. Mat. 2011, 12, 9. doi: 10.1088/1468-6996/12/3/034413

  29. [29]

      Su, D.; Meng, Q.; Vaz, C. A. F.; Han, M. G.; Segal, Y.; Walker, F. J.; Sawicki, M.; Broadbridge, C.; Ahn, C. H. Appl. Phys. Lett. 2011, 99, 102902. doi: 10.1063/1.3634028

  30. [30]

      Kavokin, A. V.; Shelykh, I. A.; Malpuech, G. Phys. Rev. B 2005, 72, 4. doi: 10.1103/PhysRevB.72.233102

  31. [31]

      Gao, P.; Ishikawa, R.; Feng, B.; Kumamoto, A.; Shibata, N.; Ikuhara, Y. Ultramicroscopy 2018, 184, 217. doi: 10.1016/j.ultramic.2017.09.006

  32. [32]

      Szot, K.; Bihlmayer, G.; Speier, W. Nature of the Resistive Switching Phenomena in TiO₂ and SrTiO₃: Origin of the Reversible Insulator-Metal Transition. In Solid State Physics; Camley, R. E.; Stamps, R. L., Eds.; Elsevier Academic Press Inc.: San Diego, CA, USA, 2014; Vol. 65, pp. 353-559. doi: 10.1016/B978-0-12-800175-2.00004-2

  33. [33]

      Kemp, W. R. G.; Klemens, P. G.; Sreedhar, A. K.; White, G. K. Proc. Roy. Soc. London A-Mat. Phys. Sci. 1956, 233, 480. doi: 10.1098/rspa.1956.0005

•