Ferroelectric properties of PZT/BFO multilayer thin films prepared using the sol-gel method
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NANO EXPRESS
Open Access
Ferroelectric properties of PZT/BFO multilayer thin films prepared using the sol-gel method Seo-Hyeon Jo1, Sung-Gap Lee1* and Young-Hie Lee2
Abstract In this study, Pb(Zr0.52Ti0.48)O3/BiFeO3 [PZT/BFO] multilayer thin films were fabricated using the spin-coating method on a Pt(200 nm)/Ti(10 nm)/SiO2(100 nm)/p-Si(100) substrate alternately using BFO and PZT metal alkoxide solutions. The coating-and-heating procedure was repeated several times to form the multilayer thin films. All PZT/ BFO multilayer thin films show a void-free, uniform grain structure without the presence of rosette structures. The relative dielectric constant and dielectric loss of the six-coated PZT/BFO [PZT/BFO-6] thin film were approximately 405 and 0.03%, respectively. As the number of coatings increased, the remanent polarization and coercive field increased. The values for the BFO-6 multilayer thin film were 41.3 C/cm2 and 15.1 MV/cm, respectively. The leakage current density of the BFO-6 multilayer thin film at 5 V was 2.52 × 10-7 A/cm2. Introduction Multiferroic materials, which exhibit simultaneously ferroelectric, ferromagnetic, antiferromagnetic, and ferroelastic behaviors, provide opportunities for potential applications in information storage, spintronic devices, and sensors [1]. Bismuth ferrite (BiFeO3) [BFO] is one such multiferroic material. BFO exhibits a distorted perovskite structure with rhombohedral symmetry. It belongs to the R3c space group with a unit cell parameter a = 0.5643 nm and a = 59.348° [2]. One of the striking features of BFO materials is the coexistence of ferroelectric (Tc = 1,123 K) and antiferromagnetic orderings (TN = 643 K) at room temperature due to a residual moment from a canted spin structure [3]. BFO is attracting great attention as a promising ferroelectric material for high-density FeREMs because of its large remanent polarization. However, BFO has serious problems as a ferroelectric material, having quite a large leakage current density, especially at room temperature. Therefore, dielectric breakdown occurs easily even at a low field, thereby indicating the difficulty in poling films. Furthermore, the highly electrically conductive nature of BFO makes it difficult to obtain excellent ferroelectric properties. To overcome this problem, various approaches have been proposed, including a substitution technique using Mn, Ti at the B-site, and/or La and Nd at the A-site * Correspondence: [email protected] 1 Department of Ceramic Engineering, Engineering Research Institute, Gyeongsang National University, Jinju-Si, 660-701, South Korea Full list of author information is available at the end of the article
[4,5] and the formation of a solid solution with Pb(Zr, Ti) O3 and BaTiO3 compositions [6]. There are many reports on the reduction of the leakage current induced by doping and the formation of a solid solution. In these investigations, the capacitor structure formed from the metal-insulator-metal structure is used for current measurement. It should be noted that current measured
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