Bi_ (3.6) Ho_ (0.4) Ti_3O_ (12) Pulsed laser deposition of thin film ferroelectric properties

Title: Bi_ (3.6) Ho_ (0.4) Ti_3O_ (12) Pulsed laser deposition of thin film ferroelectric properties
　　Author: Fu Li
　　Degree awarded: Wuhan University of Technology
　　Keywords: Bi_ (4-x) Ho_xTi_3O_ (12) target;; Bi_ (3.6) Ho_ (0.4) Ti_3O_ (12) film;; Pulsed laser deposition;; ferroelectric properties
　　Summary:
　　Bi4Ti3O12 rare earth doped ferroelectric film as a lead-free, excellent functional materials, is expected to replace lead zirconate titanate (PZT) and strontium bismuth tantalate (SBT) thin film materials, such as ferroelectric random access memory functional device Magnetic lifter was applied. Papers to Ho-doped Bi4Ti3O12 (Bi3.6Ho0.4Ti3O12) thin films and their ferroelectric properties for the research objectives, to solid-state reaction and sintering of the Ho-doped Bi4Ti3O12 ceramic target, prepared by pulsed laser deposition technique Bi3 .6 Ho0.4Ti3O12 film to look forward to a new generation of storage applications to provide an environment friendly, good ferroelectric properties of new materials.
　　Paper first to Bi2O3, TiO2 and Ho2O3 powder as raw material, the use of solid-state reaction synthesis of different Ho doping Bi4-xHoxTi3O12 powder, and then using hot-pressing densification technology to study the synthesis and sintering process parameters ( synthesis temperature, sintering temperature, Bi excess) and the amount of Ho doping on Bi4-xHoxTi3O12 powders and ceramics structure and properties, and to determine the suitability of the preparation process: first in the Bi2O3 excess 3wt%, synthesis temperature of 900 ℃, heat time 8h synthesized Bi4-xHoxTi3O12 powder; then at 850 ℃-30MPa powder sintering under 2h been Bi4-xHoxTi3O12 ceramics. Obtained under the above conditions Bi3.6Ho0.4Ti3O12 ceramic phase single, compact structure (density 99.4%), as a quality target, further preparation Bi3.6Ho0.4Ti3O12 ferroelectric thin films. Dielectric and ferroelectric properties of the test showed that with the increase in the amount of Ho doping, Bi4-xHoxTi3O12 ceramic grains gradually decreases, the density also decreased slightly, the dielectric constant and remanent polarization were increased at first and and then decreased, while the dielectric loss is first reduced and then increased. Appropriate amount of Ho doping 0.4 at 1MHz test frequency, Bi3.6Ho0.4Ti3O12 ceramic dielectric constant of 207.3, the dielectric loss of 0.0066, remanent polarization of 6.96μC/cm2.
　　Secondly, single phase, the overall density of Bi3.6Ho0.4Ti3O12 ceramic target, further use of pulsed laser deposition technique on Pt (111) / Ti/SiO2/Si substrate preparation Bi3.6Ho0.4Ti3O12 ferroelectric thin films, focuses on the deposition process parameters (laser energy density, substrate temperature, oxygen pressure) on the membrane phase, crystal orientation, surface morphology and ferroelectric properties. The results showed that with the substrate temperature, film crystallinity changed for the better, 600 ℃ and 700 ℃, can be single phase, crystalline sound Bi3.6Ho0.4Ti3O12 film, and film, respectively, were c-axis preferred orientation and random http://www.999magnet.com/products/131-magnetic-lifter orientation; with the laser energy density increased, the deposited film gradually from Bi2Ti2O7 Bi4Ti3O12 pyrochlore phase into perovskite phase, higher than 24.53J/cm2, you get a single phase of Bi3.6Ho0.4Ti3O12 film; improve the availability of single-phase oxygen pressure of Bi3.6Ho0.4Ti3O12 film, and film grain first increases and then decreases, while the crystalline orientation of no significant change. Pulsed laser deposition conditions suitable for the 29.3J/cm2-700 ℃-10Pa, in the conditions Bi3.6Ho0.4Ti3O12 single ferroelectric thin film phase, surface roughness density, but also has a large remanent polarization (22.74μC / cm2).
　　Degree Year: 2010