Charge compensation phenomena for polarization discontinuities in ferroelectric superlattices

¹ Center for Theoretical and Computational Physics, Department of Physics, University of Malaya 50603 Kuala Lumpur, Malaysia
² School of Materials Science and Engineering, The University of New South Wales - NSW 2052, Australia
³ School of Physics, Universiti Sains Malaysia - 11800 Minden, Penang, Malaysia
⁴ Department of Engineering Physics, Electronics and Mechanics, Graduate School of Engineering, Nagoya Institute of Technology - Nagoya 4668555, Japan

^(a) khchew@um.edu.my

Received: 13 September 2014
Accepted: 4 December 2014

Abstract

Based on the Landau-Ginzburg theory, the screening charge compensation phenomena for polarization discontinuities at interface in ferroelectric superlattices are investigated. Interface mixing leads to polarization continuity or discontinuity in superlattices. Free charge with equal but of opposite sign for alternate interface, driven by internal electric field, builds up to counteract the depolarization effect in superlattices. The charge density depends on the degree of interface mixing, and it approaches a saturated value when the mismatch of internal field or polarization at interface vanishes. Using PbTiO₃/SrTiO₃ (PT/ST) as a model system, the charge compensation phenomena for polarization discontinuities in superlattices is investigated by examining the polarization and internal electric field profiles. Dependence of local polarization and internal field at the interfaces on screening charge density is also examined in detail.