Dissertation > Excellent graduate degree dissertation topics show

Preparation and Physical Property Investigation on Perovskite Superconductor/Ferroelectrics/Ferromagnet Films and Heterojunctions

Author: XiaFengJin
Tutor: XieZhong
School: Hunan University
Course: Physics
Keywords: pulsed laser deposition perovskite oxide electron-doped high-Tcsuperconductor manganese ferroelectric heterostructure rectification
CLC: O484.1
Type: PhD thesis
Year: 2012
Downloads: 112
Quote: 0
Read: Download Dissertation

Abstract


In this thesis,a series of highly c-oriented perovskite oxide thin films andheterostructures which are composed by high-Tcsuperconductor, ferroelectric andcolossal magnetoresistance material were fabricated by pulsed laser deposition (PLD)method, and their properties of structure, surface, interface and transport wereinvestigated. The structure of thin films was characterized by X-ray diffraction (XRD)and single phase of the films were obtained. The interfaces of these heterostructureshave been detected by Transmission electron microscopy (TEM). Atomic forcemicroscopy (AFM) and Scanning electron microscopy (SEM) were used to dectect thesurface morphology. AFM and SEM results showed that thin films with smoothlysurface were obtained. The flat surfaces are suitable for the preparation of multilayerheterostructures. The resistivities and carrier densities of LCCO and LSMO are all in104Ωcm and1021cm3orders, respectively. The IV curves and transport properties ofthese heterostructures were measured and studied by Physical Property MeasurementSystem (PPMS). The main results are listed as follows.1. La1.89Ce0.11CuO3/Ba0.5Sr0.5TiO3/La0.67Sr0.33MnO3heterostructureP-type CMR La0.67Sr0.33MnO3(LSMO), insulator Ba0.5Sr0.5TiO3(BST), andn-type high-TcLa1.89Ce0.11CuO3(LCCO) thin films were deposited on SrTiO3substrates by using PLD method. Several kinds of perovskite heterostructures havebeen studied, such as LCCO/LSMO, LCCO/BST, BST/LSMO, and LCCO/BST/LSMO.The structure and surface properties were investigated carefully by XRD, TEM, SEMand AFM. The I-V characteristics of these junctions were also investigated. The majorresults are in the following:(1) LCCO/LSMO heterostructure has no rectification,because both of them have the high carrier densities.(2) The I-V curves ofLCCO/BST, BST/LSMO heterostructures have weak asymmetry under different bias.The BST layer plays a key role in the rectification effect.(3) The significantrectification effect was obtained in LCCO/BST/LSMO p-i-n heterostructure. Therectification effect was explained by diffusion theory, energy band theory anddepletion layer theory. The rectification can be attributed to the depletion layer andcarrier density.2. La1.89Ce0.11CuO3/SrTiO3/La0.67Sr0.33MnO3heterostructureIn order to clarity the role of ferroelectric property in BST layer,La1.89Ce0.11CuO3/SrTiO3/La0.67Sr0.33MnO3trilayer heterostructures were prepared with different SrTiO3thicknesses from15nm to30nm. The I-V curves of theseheterostructures showed asymmetric at room temperature. The best rectification effectwas obtained when the thickness equal to20nm. The best thickness value calculatedby diffusion theory is21nm, which is consistent with the experimental result. Besides,the experimental results were also analyzed by the energy band theory, and itindicated that the ferroelectric property of BST is not necessary for the rectification.3. La1-xSrxMnO3/Nb-SrTiO3heterostructureThe La1-xSrxMnO3(x=0.1-0.6) thin films were deposited on0.7wt%Nb dopedSrTiO3substrates by PLD method. A series of heterostructures were fabricated bymicrofabrication techniques. The results showed that the threshold voltage wasincreased with the decrease of the temperature. The leakage current at interface candamage the rectification. The I-V characteristics under ac voltage source weremeasured at room temperature and low temperature. The I-V curves of theseheterostructures had strong asymmetry when the voltage source at low frequency, butthe rectification would be destroyed when the frequency larger than1KHz. Thecapacitance of the heterostucture was analyzed by using equivalent circuit.

Related Dissertations

  1. Research of the Performances of Ferroelectric Film and Compositional-Graded Ferroelectric Film,TM221
  2. The Application of Eggshell Membrane for Solid-phase Extraction and the Determination of Trace Metal Elements in Environment Water,X832
  3. Iron-doped SnO \u003csub\u003e 2 \u003c/ sub\u003e ceramics and thin films research,TQ174.6
  4. Calcium Barium strontium titanate ferroelectric ceramics dielectric properties of,TQ174.1
  5. Trametes sp.SQ01 and Chaetomium sp.R01 mixed culture studies on decolorization,X791
  6. Low-dimensional semiconductor nanomaterials (ZnO, TiO 2 ) Synthesis and Research,TB383.1
  7. Investigation of the Entropy Change Effect in Ferroelectrics and Multiferroics,TM221
  8. Preparation, Characterization and Catalytic Activity of Ni-Mn/γ-Al2O3 Catalyst for CO2 Methanation,O643.36
  9. Japanese learners of Chinese speech -based teaching,H195
  10. Metallogenic Geochemistry Study of the Mn Deposit in Hougou-Dapingshan in Mianxian, Shanxi Province,P618.32
  11. Study on the Regioselective Reactions of Sulfur Radical and Unsaturated Systems,O621.25
  12. Tailoring In-plane Crystallographic Orientation of Epitaxial YBa2Cu3O7-δ Thin Films Having Perpendicular C-axes Texture,TB383.2
  13. The Epitaxial Growth of C-axis Oriented YBa2Cu3O7-δ Films by Pulsed Laser Deposition and the Elimination of Laser-induced Particles,TB383.2
  14. Prepration of Manganses Dioxide and Investigation on the Performance of Supercapacitor,TM53
  15. The Research & Implementation of Obstacle Detection Algorithm Based on Binocular Stereo Vision Technique,TP391.41
  16. Magnetocaloric Effect in Pure and Doped Magnetic Relaxor Ferroelectrics CdCr2S4,O482.5
  17. Hyphenation of Sequential Injection with Spectrometry for the Determination of Trace Level of Heavy Metals,O657.99
  18. First-principles Investigation on the Structures and Properties of BiFeO3,TB34
  19. Formation of Biogenic Manganese Oxide and Oxidative Degradation of Environmental Representative Enstrogens,X703
  20. A Study on Highly Oriented AlN Thin Film Prepared by Pulsed Laser Deposition,O484.1
  21. Photovoltaic effect on the BaTiO 3 ferroelectric properties of thin films,O484.4

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