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by Sara Rothwell Mentor : Bin Liu Advisor: Prof. Dravid July 2, 2008

Nanopatterning of Multiferroic Oxides via “Soft” Electron Beam Lithography. by Sara Rothwell Mentor : Bin Liu Advisor: Prof. Dravid July 2, 2008. R. Ramesh; N. Spaldin. Nature Materials 6 (2007) 23. VPD Group. NU ANCE Center. Multiferroic oxides.

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by Sara Rothwell Mentor : Bin Liu Advisor: Prof. Dravid July 2, 2008

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  1. Nanopatterning of Multiferroic Oxides via “Soft” Electron Beam Lithography by Sara Rothwell Mentor:Bin Liu Advisor: Prof. Dravid July 2, 2008 R. Ramesh; N. Spaldin. Nature Materials6 (2007) 23. VPD Group NUANCE Center

  2. Multiferroic oxides • Materials that have coupled electric, magnetic and structural order parameters that result in simultaneous ferroic properties (i.e. ferroelectric, ferromagnetic, or ferroelastic). • Future applications include data storage, communications, and spintronics. J. Wang et al. Science299 (2003)1721. VPD Group NUANCE Center

  3. Multiferroics cont… • Naturally occurring single phase multiferroics: BiFeO3, hexagonal HoMnO3 • BiFeO3 is ferroelectric and anti- ferromagnetic at room temperature • Possible synthetic multiferroics: • Alternate thin layers: • BaTiO3 and Fe3O4 or CoFe2O4 • Multiferroic by substitution • Dope BaTiO3 with magnetic Mn, Fe, or Co ion O2- Mn3+ Ho3+ J. Wang et al. Science299 (2003) 1719. VPD Group NUANCE Center

  4. “Soft” Electron Beam Lithography Double layer of photoresist Nanopatterning of resist With electron beam Sol-gel applied to nanopatterned surface. Spin the sample to distribute sol-gel evenly Lift off photoresist Heat treatment • Advantages • Sol-gel is a low cost, room temperature fabrication method for metal oxides • Double layer creates a controlled undercut • Site specificity Tao Sun et al. Appl. Phys. Lett.89 (2006) 163117. VPD Group NUANCE Center

  5. Research questions • How do multiferroic properties change when patterned on the nanoscale? • Can we create synthetic multiferroics on the nano scale in which ferroelectric and ferromagnetic properties are connected? Summer work: • Properties of BaTiO3 doped with magnetic ions • Properties of horizontal/vertical heterostructures of BaTiO3 and CoFe2O4 VPD Group NUANCE Center

  6. Methods • Combine BaTiO3 and CoFe2O4 sol-gels • Make nano-dots from varying % mixtures using “soft”eBL • Test for crystallinity using X-ray powder diffraction • Find magnetic and electric hysteresis loops with PFM and MPSM VPD Group NUANCE Center

  7. Methods cont… • Add Co3+, Mn3+, and Fe3+ ions to BaTiO3 sol-gel • Add ions during synthesis to encourage full incorporation • Again, make nano-dots from varying % molar ratio mixtures and test hysteresis loops VPD Group NUANCE Center

  8. Nanodots 500 nm Nanodots from 50% CoFe2O4 VPD Group NUANCE Center

  9. XRD Powder Results: CoFe2O4 mixtures Orange: 90% CoFe2O4 Blue: 50% CoFe2O4Green: 20% CoFe2O4 VPD Group NUANCE Center

  10. XRD Powder Results:BaTiO3 doped with magnetic ions Reds: Iron doped BaTiO3 Greens: Cobalt BaTiO3 Oranges: Manganese BaTiO3 VPD Group NUANCE Center

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