Abstract
Effects of defect on ferroelectric stability in PbTiO3 (PTO) thin
films have been investigated using molecular dynamics with first-principles
effective Hamiltonian. In this paper, oxygen vacancy (Vo) has been considered to
study the hysteresis loop, spontaneous polarization as a function of film
thickness. Vo has been modeled as a charged point defect. Density functional
theory (DFT) calculations are performed to determine the Vo-induced localized
fields (both mechanical and electrical) and the calculated DFT results are used
as inputs to molecular dynamics simulations in a large system. The strain field
induced by the Vo is calculated by DFT calculations and fitted by the continuum
strain modeling, and the electrostatic field is given by the superposition of
the Vo-induced field and the external field. Vo significantly reduces the
spontaneous polarization and increases the critical thickness.