Structural and electrical properties of c-axis epitaxial and polycrystalline Sr3Bi4Ti6O21 thin films

Abstract

c-axis epitaxial and polycrystalline Sr3Bi4Ti6O21 (SBTi) thin films were fabricated on (001)SrTiO3 (STO) single-crystal substrates and Pt/Ti2/SiO2/Si substrates respectively, by pulsed laser deposition (PLD). Structures of the films were systematically characterized by x-ray diffraction (XRD), including θ-2θ-scans, rocking curve scans and φ-scans, atomic force microscopy and transmission electron microscopy (TEM). The epitaxial orientation relation of the SBTi films on STO is established by selected-area electron diffraction and XRD φ-scans to be (001)SBTi ∥ (001)STO, [11̄0]SBTi ∥ [010]STO. Cross-sectional high-resolution TEM studies on the epitaxial SBTi film revealed that SBTi is a single-phase material. A special kind of irrational atomic shift along the [001] direction was observed and is discussed in detail. By using an evanescent microwave probe (EMP), the room-temperature dielectric constant of the epitaxial SBTi film was measured to be 211 ± 20. Excellent electrical properties of the polycrystalline SBTi films with Pt bottom and top electrodes were exhibited: the Pr and Ec values were 4.1 μC cm-2 and 75 kV cm-1 respectively, the nonvolatile polarizations decreased by less than 5% after 2.22 × 109 switching cycles and the dielectric constant and loss tangent were 363 and 0.04 at 100 kHz.