Effect of Substrates on the Structure and Ferroelectric Properties of Multiferroic ${\hbox{BiFeO}}_{3}$ Films

Abstract

Structure and ferroelectric properties of multiferroic BiFeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (BFO) films prepared by pulse laser deposition (PLD) with different substrates of Pt/Ti/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Si(100) and Pt/glass have been studied. Isotropic perovskite BFO phase is obtained in the 200-nm-thick BFO films deposited on both substrates at reduced substrate temperature T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> = 400-500°C. Uniformly finer grains and smoother surface are obtained for BFO films grown on Pt(111)/glass as compared to Pt/Ti/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Si(100) substrate. This difference may be related to the distinct BFO/Pt interface morphology. After postannealing, the Pt layer grown on glass substrates has very smooth surfaces consisting of (111) grains, while it contains cracks in the Pt/Ti/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Si(100). As a result, lower leakage current density and better ferroelectric properties of 2P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> = 15.1-78.6 μC/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> = 383-514 kV/cm are obtained in the BFO films deposited on Pt(111)/glass substrates. Nevertheless, high deposition temperature of 550°C leads to the formation of large amount of BFO into Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9</sub> , and Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> phases, and therefore, no ferroelectric behavior is observed.