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X-ray structural analysis

Near-surface structural changings in paratellurite crystals under external electric field

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  • Mr. Anton KULIKOV

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Content

This work describes the results of the near-surface structural changes caused by the migration of oxygen vacancies in paratellurite (α-TeO2) single crystals obtained by the in situ X-ray diffraction technique under a constant electric field. This process has a reversible character [1] and its dynamics (duration is about tens of minutes) corresponds with the conductivity kinetics.

When the electric field is applied along the [100] and [110] directions, two types of processes occurs simultaneously which were recorded through measurement of the diffraction curve evolution [2]. The first one is caused by the piezoelectric lattice deformation due to a sharp increase in the strength of the field near both surfaces. At the same time, the change in the lattice parameter near the anode (the surface of a crystal with a positive external charge) was revealed, that is caused by a local rearrangement of the crystal structure due to the counter migration of oxygen ions and oxygen vacancies in the external electric field and their accumulation at the dielectric-metal interface. The velocity of the process depends on the crystallographic direction, however the application of electric field in the non-piezoelectric direction [001] does not affect on the rocking curve shape.

This work was partially supported by the Russian Foundation for Basic Research (RFBR grant № 18-32-00410 mol_a, 16-32-60045 mol_a_dk) and by the Federal Agency of Scientific Organizations (Agreement № 007-ГЗ/Ч3363/26) in part of crystal growing and sample preparation.

References:

  1. M. V. Kovalchuk, A. E. Blagov, A. G. Kulikov, et al. // Crystallography Reports. 2014. V. 59(6). pp. 862–866
  2. A. G. Kulikov, A. E. Blagov, N. V. Marchenkov, et al. // JETP Letters. 2018. V. 107(10). pp. 679 – 683