Dissertation > Excellent graduate degree dissertation topics show

Preparation and Characterization of BixFeO3（0.80≤x≤1.20） Thin Films

Author: LiXiao
Tutor: YangPingXiong
School: East China Normal University
Course: Microelectronics and Solid State Electronics
Keywords: BixFeO3thin films Sol-gel technique microstructure opticalproperties ferroelectricity
CLC: O484.1
Type: Master's thesis
Year: 2012
Downloads: 51
Quote: 0
Read: Download Dissertation

Abstract


During the recent decades, there has been a spurring trend of research about multiferroic materials. These materials are specialized for possessing ferroelectricity, ferromagnetism or even ferroelasticity spontaneously at the same time. As one of the multiferroic materials, lead-free bismuth ferrite (BiFeO3BFO) has attracted numerous attentions for its relatively large remnant polarization (Pr～100μC/cm2), high Curie temperature (TC～850℃) and high Neel temperature (TN～370℃). These properties make BFO a very promising candidate in the development and application of new-generation multi-function devices.To prepare BFO thin film samples, there are several experimental methods such as sol-gel technique, pulsed laser deposition, magnetron sputtering and molecular beam epitaxy, etc. Each method has its own advantages, but there are still bottlenecks to obtain high-quality pure BFO samples. One of the bottlenecks is the volatility of bismuth which usually leads to off-stoichiometry effects on BFO thin films and so there will be unbearable high conductivity in BFO samples. As a result, even though BFO has been discovered since1960s, there’s still little notable progress in its application in devices.A long used step to avoid the influences brought by the volatility of bismuth is to use overdosed bismuth to prepare BFO samples. However, the effect is limited since the impurities cannot be eliminated completely. Hence, to examine the influences of the variation of bismuth composition on crystallization, microstructure, optical and electrical properties of BFO thin films, we started an investigation on BixFeO3thin films prepared by sol-gel technique with x changing from0.80to1.20. Main results are as follows:(1) We have successfully prepared the precursors solution of BixFeO3with x varying from0.80to1.20using sol-gel technique. The BixFeO3thin films were deposited on both Si(100) and LNO/Si(100) substrates. In addition, we also prepared5%La doped BixLa0.05FeO3samples on both substrates to observe how can stoichiometry variation effect doped BFO thin films.(2) The XPS test was adopted to examine that if the ratios of Bi atoms and Fe atoms in the samples were in accordance with our anticipation. The results indicated an excess of bismuth on the surfaces but a lack of bismuth in the inside. Using X-ray diffraction (XRD) technique and atomic force microscope (AFM), we observed the microstructures and surface morphologies of our BixFeO3thin films. We only obtained pure BFO structure without any impurity phases when x was1.00according to our XRD patterns. Meanwhile, there appeared to be a change in the rhombohedral distortion with bismuth content reaching towards both extremes. AFM pictures clearly showed the surfaces of our samples changing with the increasing x value.(3) Raman spectra and spectroscopic ellipsmetry measurements were used to study the influences of variation of bismuth composition on the optical properties of BixFeO3thin films. In Raman spectra, we have identified most of the Raman active mode of BFO. The observed variation of active modes can be generally attributed to the changing of both Bi-O and Fe-O covalent bonds. In addition, by fitting the spectroscopic ellipsmetry data we obtained the refractive index n and extinction coefficient k. The shifting of n indicated a change of strain in BixFeO3thin films with x varying from0.80to1.20. Optical band gaps (Eg) were obtained by Tauc plot. With x increase from0.80to1.20, the optical band gap of BixFeO3thin films increase at first, and then fall down. Possible cause is the changed lattice parameter brought by appearances of impurities.(4) We also performed some electrical tests to examine the ferroelectricity and dielectricity of our BixFeO3samples as well as BixLaFeO3samples. We used LNO thin films as the bottom electrodes and sputtered Pt as the top electrodes. The results showed an increasing Pr with the higher x value in BixFeO3samples. While in BixLaFeO3samples Pr stopped increase when x reached0.95and started to fall down with the further increase of x.

Related Dissertations

  1. Reactive Hot-Pressing and Mechanical Properties of （ZrB2-ZrO2）/BN Composites,TB332
  2. Microstructure and Mechanical Properties of Mg-Zn-Y-Zr Alloys,TG146.22
  3. Investigation on Microstructure and Properties of Cadmium-Free Silver-Based Intermediate Temperature Filler Metals,TG425.2
  4. Research on Technology and Mechanism of Joining Cemented Carbide to Carbon Steel,TG454
  5. The Investigations on the Characteristics and Mechanism of NIR Emission from Bi-doped Silicophosphate Glasses,TQ171.1
  6. Preliminary Study on Salt-Tolerant Mechanism of the New Pennisetum Purpereum Schumach Variety-Sumu No.2,S543.9
  7. Study on the Fine Structure of Intestine and Intestinal Mucosal Barrier in Zebrfish (Brachydanio Rerio),Q95-33
  8. Study on Characteristics of Morphology Anatomy and Physio-Biochemistry of Two Ecotype Varieties Cucumber Leggy Seedilings,S642.2
  9. Study on the Mechanism of Heat-Induced Gelation of Myofibrillar Proteins,TS251.1
  10. Studies on the Aggregation and Microstructure of Imidazolium Ionic Liquids in Solutions,O645.1
  11. Chinese word for international education research based lexicography,H164
  12. The Effect of Tungsten on Microstructures and Properties of Wear Resistant Overlays Prepared by Plasma Cladding,TG174.4
  13. Study on the Structure and Electrical Properties of the Doping NiCo0.2Mn1.8O4 Spinel Type,O614.81
  14. Research and Development of Spidroin/Poly-L-lactic Acid Composite Nanofiber,R318.08
  15. Studies of Luminescence Characteristics of Eu3+-doped Rare Earth Borates REBaB9O16 （RE=rare Earth Ions and Y）,O627.3
  16. The Research on Extrusion Parameters Through the Plate Billet of Magnesium Alloy,TG379
  17. Study of the Polymer Synthetic Paper Formula and Papyraceous Performance,TS71
  18. Study on Microstructure and Superconducting Properties of MgB2 Wires Fabricated by Two-Step PIT,TM26
  19. Study on Morphological Evolution and Toughening Mechanism of Sandbag Microstructure-toughened PA6/EPDM-M/nano-CaCO3 Ternary Composites,TB33
  20. The Photoluminescence of H1.77 [Sr0.8 Bi0.21Ta2 O7] Nano-layers Annealing under Different Temperatures and the Effect of the Cu2O Addition on Its Photocatalytic Activity,O482.31
  21. Compressive Strengthes and Microstructural Characteristics of Fiber Reinforced Geopolymer,TB321

CLC: > Mathematical sciences and chemical > Physics > Solid State Physics > Thin Film Physics > Film growth,structure and epitaxy
© 2012 www.DissertationTopic.Net  Mobile