First-principles study of two-dimensional electron and hole gases at the head-to-head and tail-to-tail 180 domain walls in PbTiO3 ferroelectric thin films

James Sifuna, Pablo García-Fernández, George S. Manyali, George Amolo, and Javier Junquera
Phys. Rev. B 101, 174114 – Published 28 May 2020

Abstract

We study from first principles the structural and electronic properties of head-to-head (HH) and tail-to-tail (TT) 180 domain walls in isolated free-standing PbTiO3 slabs. For sufficiently thick domains (n=16 unit cells of PbTiO3), a transfer of charge from the free surfaces to the domain walls to form localized electron (in the HH) and hole (in the TT) gases in order to screen the bound polarization charges is observed. The electrostatic driving force behind this electronic reconstruction is clearly visible from the perfect match between the smoothed free charge densities and the bound charge distribution, computed from a finite difference of the polarization profile obtained after the relaxation of the lattice degrees of freedom. The domain wall widths, of around six unit cells, are larger than in the conventional 180 neutral configurations. Since no oxygen vacancies, defects, or dopant atoms are introduced in our simulations, all the previous physical quantities are the intrinsic limits of the system. Our results support the existence of an extra source of charge at the domain walls to explain the enhancement of the conductivity observed in some domains walls of prototypical, insulating in bulk, perovskite oxides.

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  • Received 4 April 2020
  • Revised 11 May 2020
  • Accepted 12 May 2020

DOI:https://doi.org/10.1103/PhysRevB.101.174114

©2020 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

James Sifuna1,2,3,*, Pablo García-Fernández1, George S. Manyali4, George Amolo3, and Javier Junquera1,†

  • 1Departamento de Ciencias de la Tierra y Física de la Materia Condensada, Universidad de Cantabria, Cantabria Campus Internacional, Avenida de los Castros s/n, 39005 Santander, Spain
  • 2Department of Natural Science, Catholic University of Eastern Africa, 62157-00200 Nairobi, Kenya
  • 3Materials Modeling Group, Department of Physics and Space Sciences, Technical University of Kenya, 52428-00200 Nairobi, Kenya
  • 4Computational and Theoretical Physics Group, Department of Physical Sciences, Kaimosi Friends University College, 385-50309 Kaimosi, Kenya

  • *sifunajames@gmail.com
  • javier.junquera@unican.es

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Issue

Vol. 101, Iss. 17 — 1 May 2020

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