Fabrication of (Fe,Zn)3O4 -BiFeO3 nano-pillar structure by selfassembled growth Tanaka Laboratory Takuya Sakamoto Contents • Research background(spintronics) • • • • Functional oxides in 1-dimensional structure Nano-pillar structure Self-assembled method My research • Summary and future plan Research background (spintronics) Electronics Magnetics charge e- Spin and charge (Fe,Zn)3O4/Pb(Zr,Ti)O3 spintronics Ferromagnetic semiconductor Magnetism depends on carrier concentration e- e- e- e- e- e- e- Ｅ ferroelectrics Sponteneos electric polarization Functional oxide is attractive !! Modulation of magnetism by electric field 田中秀和等, 機能材料 28 54 (2008) Functional oxides in 1-dimensional structure Average properties in 2-dimensional structure domain AFM Single domain properties in 1-dimensional structure AFM FM 100nm FM (La,Ca)MnO3 M. Fäth, et.al, Science 285 1540 (1999) Yanagisawa et.al, Appl.Phys.Lett 89 253121 (2006) Nano-pillar structure Nano-pillar structure Average properties in 2-dimensional structure Single domain properties in 1-dimensional structure Self-assembled method Self-assembled method Top down method Phase separation Mixed state spinel perovskite Wetting condition Self –assembly growth using difference of wetting condition perovskite spinel Haimei Zheng et.al, Nano.Lett 6 1401(2006) My research • （１）fabrication of nano-pillar structure target：(BiFeO3)0.65(Fe2.2Zn0.8O4)0.35 ferroelectrics Ferromagnetic semiconductor ＰＬＤ装置(ArF excimer laser) substrate：SrTiO3(100) substrate temperature：400℃～700℃ Oxygen pressure：0.01Pa～10Pa • （２）crystal structure x-ray diffraction (θ-2θ) • （３）surface structure Atomic Force Microscope (AFM) Scanning Electron Microscope (SEM) Result 1 (crystal structure) Optimized deposition condition STO 105 ＢＦＯ STO (100) (100) ＢＦＯ (200) ＦＺＯ = (Fe2.2Zn0.8O4) (200) ＦＺＯ (400) 104 ＢＦＯ = BiFeO3 103 STO = SrTiO3 102 101 10 20 30 40 50 2θ Both epitaxial FZO and BFO could be grown on STO by self-assembly method. 60 Result2 (surface structure) Surface SEM image cross section SEM image BiFeO3 (Fe,Zn)3O4 ２μm Surface AFM image FZO BFO Interface STO 500 nm EPMA(Electron Probe Micro Analyzer) Nano-pillar structure was obtained Summary • Nano-pillar structure was obtained by self-assembled method Future plan • Nanopillar structure by self-assembly growth has possibility to control single domain properties and to enhance the efficiency of magnetism modulation.
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