Search

The stress influence of the structural and ferroelectric properties of polycrystalline BiFeO3 (BFO) thin films has been investigated using a membrane substrate for relaxing stress. Reciprocal space mapping (RSM) measurement has been performed to confirm the stress dependence of the crystal structure of polycrystalline BFO thin films on the Pt (200 nm)/TiO2 (50 nm)/SiO2 (600 nm)/Si (625 μm) substrate (stress-constrained BFO film) and the Pt (200 nm)/TiO2 (50 nm)/SiO2 (600 nm)/Si (15 μm) membrane substrate (stress-relaxed BFO film). The BFO thin films prepared by pulsed laser deposition were polycrystalline and mainly exhibit a texture with (001) and (110) plane orientations. From the RSM results, the crystal structure of the (001)-oriented domain changes from Pm monoclinic to Cm monoclinic or to R3c rhombohedral due to stress relaxation. Moreover, at room temperature as well as at 150 K, remanent polarization (Pr) increases and double coercive field (2Ec) decreases (in the latter case from 88 to 94 μC/cm2 and from 532 to 457 kV/cm, respectively) due to relaxing stress. The enhancement of ferroelectricity is attributed to the crystal structural deformation and/or transition and angle change between the polarization direction and film plane. [ABSTRACT FROM AUTHOR]

Polycrystalline BiFeO3(BFO) films on Pt/TiO2/SiO2/Si substrate have been prepared by a pulsed laser deposition (PLD) method with various repetition rates. The X-ray diffraction (XRD) pattern observes single-phase perovskite structure with a small secondary phase. While the film-thickness is increased with increasing repetition rates, the grain size increases, and the leakage current reduces. Also, good polarization versus electric field (P-E) hysteresis loops of all polycrystalline BFO films were obtained at room temperature (RT). It is seen that the polarization value (Pr) practically remains almost constant for all the BFO films, and the coercive field (Ec) decreases with increasing the film thickness. [ABSTRACT FROM PUBLISHER]

Sr-substituted BiFeO3 thin films (BSFO) have been prepared on Pt/TiO2/SiO2/Si substrate by pulsed laser deposition using 15% Bi-excess targets (Bi1.15(1-x)SrxFeO3). Some XRD peaks shift to low angle with increasing Sr, and grain sizes decrease. Leakage current densities of BSFO thin films are almost same or a little larger compared to that of BiFeO3 thin film, but P-E hysteresis loops were obtained at RT and 80 K. M-H hysteresis loops of BSFO thin films show weak ferromagnetism at RT and 80 K. BSFO thin film for x = 0.05 shows good multiferroic properties including ferroelectricity and ferromagnetism. [ABSTRACT FROM AUTHOR]

Multiferroic 350-nm-thick BiFeO3 thin films have been prepared on Pt/TiO2/SiO2/ Si(54 μm) membrane substrates by pulsed laser deposition. To confirm the influence of stress from substrate, ferroelectric and magnetoelectric properties of BiFeO3 thin films have been evaluated with applying stress. For applying stress, we tried to pump out backside of the membrane structure at various pressures. From ferroelectric hysteresis loops, the remanent polarization at the pumping pressure of 0.01 atm increase from 105 to 110 μC/cm2, comparing to that without pumping. Under magnetic field of 0.4 T, polarization at zero electric field at pumping pressure of 0.01 atm with maximum applied voltage of 15 V increased from 100 μC/cm2 to 103 μC/cm2. [ABSTRACT FROM AUTHOR]

Abstract: BiFe1 −x Zn x O3 (BFZO) thin films (x = 0, 0.05, and 0.1) have been prepared on Pt/TiO2/SiO2/Si substrate by pulsed laser deposition and their multiferoic properties have been investigated. BFZO thin films shows polycrystalline perovskite single phase. The grains become small with increasing the substitution of Zn, and leakage current of BFZO thin film for x = 0.05 was lower than that of BiFeO3 thin film. The dielectric constant of BFZO thin films for x = 0, 0.05, and 0.1 are 107, 146, and 170 at room temperature, respectively. P-E hysteresis loops were obtained at room temperature and 80 K, and Pr slightly increases at low frequency from 500 Hz to 20 kHz. M-H hysteresis loops show weak ferromagnetic properties at 300 K and 80 K by substitution of Zn. [Copyright &y& Elsevier]