Phenomenological modeling of anisotropic dielectric properties in epitaxial (Pb, Sr)TiO3 thin films

Yecheng Ding,Wenhui Ma

doi:10.1063/1.5126727

Abstract

Strain tuning of polarization states and dielectric properties in (001) epitaxial (Pb, Sr)TiO3 (PST) films is investigated using a thermodynamic phenomenological model. We find that our calculations of anisotropic dielectric properties and their electric field tunability at various in-plane strained states are in good agreement with relevant experimental data for epitaxial Pb0.35Sr0.65TiO3 films when material constants are properly determined. Our modeling further suggests that dielectric tunability can be optimized by combined control of epitaxial strain and PST composition.

Highlights

The present work is focused on modeling anisotropic dielectric properties measured in epitaxial PST35/65 subjected to anisotropic in-plane strain.[11,12]
Strain relaxation and its potential influence on the structure scitation.org/journal/adv calculations using a number of a0 were made to find the most appropriate lattice constant for stress-free paraelectric cubic PST35/65
In order to compare our theoretical results with experimental results on strain relaxed epitaxial films,[11,12] rather than the misfit strain defined in Ref. 3 for coherently grown and fully strained films, in-plane strain deduced from deformation of the thin film lattice with respect to the strain-free paraelectric cubic reference and properties are a fairly interesting topic

Summary

Introduction

Epitaxial strain can be used to manipulate structural transition and physical properties of ferroelectric thin films, such as enhancement of Curie temperature (Tc) and spontaneous polarization (Ps),[1,2] occurrence of new phases,[3] tuning of dielectric properties,[4,5] strain-driven morphotropic phase boundary (MPB)[6,7,8] and critical phenomena,[9] and orientation control of phase stability and ferroelectricity.[10]Epitaxial thin films of lead strontium titanate (PbxSr1−xTiO3 or PST) have been prepared and characterized by a number of researchers[11–19] mainly because of unique dielectric properties and high potential for tunable microwave device applications.[20–29] Interestingly, recent theoretical studies[30] revealed existence of the rhombohedral phase and low-temperature MPB in PST solid solution.Experimentally, a number of methods can be used to change in-plane epitaxial strain, such as selection of substrates and control of cooling rate. They constructed a misfit strain phase diagram for epitaxial PST35/65 and calculated zero-field in-plane dielectric anisotropy for the FC sample.[11] It would be interesting if one can fully model the E-field tunability of anisotropic dielectric properties and study the effect of strain relaxation by comparing results on both the FC and SC samples.[11,12]

Objectives

Results

Conclusion