Weak dependence of spontaneous polarization on epitaxial strain in ferroelectric BiAlO3: A first-principles study

Abstract

We investigate the effects of epitaxial strain on the ferroelectric properties of BiAlO3 (BAO) using first-principles calculations. We find a large polarization (P) of 72.3 μC/cm2 as well as a small energy barrier of ∼0.1 eV/formula unit for coherent ferroelectric switching of unstrained BAO. Thus, this material is suitable for applications in high-speed nonvolatile memory. We study the modification of P due to epitaxial strains of −5 to +5%, where the minus and plus signs represent the compressive and tensile strains, respectively. The polarization of BAO is insensitive to epitaxial strain; the polarization change is limited to below ∼6%. The weak sensitivity of the polarization is attributed to the stereochemical activity of Bi 6s2 lone pairs as well as the inertness of the B-site Al to the polarization. The strain application modifies the switching energy barrier by up to 30%, which provides guidelines for design of devices based on BAO.