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by Sara Rothwell Mentor : Bin Liu Advisor: Prof. Dravid August 21, 2008

The Sol-gel Synthesis of Multiferroic Materials. by Sara Rothwell Mentor : Bin Liu Advisor: Prof. Dravid August 21, 2008. VPD Group. NU ANCE Center. O. Outline. What are multiferroics? What techniques are used? Sol-gel, e BL, XRD Results so far… Future work Research question

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by Sara Rothwell Mentor : Bin Liu Advisor: Prof. Dravid August 21, 2008

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  1. The Sol-gel Synthesis of Multiferroic Materials by Sara Rothwell Mentor:Bin Liu Advisor: Prof. Dravid August 21, 2008 VPD Group NUANCE Center

  2. O Outline • What are multiferroics? • What techniques are used? • Sol-gel, eBL, XRD • Results so far… • Future work Research question • Can we create nano-scale multiferroic structures in which ferroelectric and ferromagnetic properties are connected at room temperature? VPD Group NUANCE Center

  3. Multiferroic ceramics • Materials with: • Simultaneous ferroic properties (i.e. ferroelectric, ferromagnetic, or ferroelastic). • Single phase or multiple phase materials: BiTiO3, oralternating thin films or heterostructures • Sol-gels: • suspended solution of desired precursor • Future applications of multiferroics: • Data storage, communications, sensors, resonators, power control devices… VPD Group NUANCE Center

  4. Summer Work • Mix ferromagnetic CoFe2O4 and ferroelectric BaTiO3 sol-gels in ratios • Investigate phase content using x-ray diffraction • Make nano-dots using eBL and test magnetic and electrical properties • Dope ferroelectric BaTiO3 with magnetic Mn, Fe, or Co ions • Investigate phase content using x-ray diffraction • Make nano-dots using eBL and test magnetic and electrical properties. Possible two-phase multiferroic Possible single phase multiferroic VPD Group NUANCE Center

  5. “Soft” Electron Beam Lithography Double layer of resist Nanopatterning of resist With electron beam Sol-gel applied to nanopatterned surface. Spin the sample to distribute sol-gel evenly Lift off resist Anneal to condense and crystallize • Advantages of combined sol-gel and eBL use • Low cost, room temperature, versatile, simple execution • Double layer creates controlled undercut • Site specificity VPD Group NUANCE Center

  6. XRD Powder Results: CoFe2O4 mixtures BTO <101> <110> Purple: 90% CoFe2O4 Blue: 50% CoFe2O4Green: 20% CoFe2O4 CFO <311> BTO <112> <211> BTO <001> <100> CFO <220> CFO <440> CFO <400> CFO <511> BTO <202> <220> BTO <200> BTO <201><210> CFO <422> BTO <111> Peaks are from two phases only! VPD Group NUANCE Center

  7. XRD Powder Results:BaTiO3 doped with magnetic ions Peaks are from BaTiO3 only! <001> <100> <101> <110> <111> <200> <201> <210> <112> <211> <202> <220> VPD Group NUANCE Center

  8. BaTiO3 doped with magnetic ions: Mn peaks <112> <211> <111> Brown: 10% Mn Orange: 5% Mn Gold: 1% Mn <200> <202> <220> <201> <210> VPD Group NUANCE Center

  9. EDS Element Maps • Thin film of BaTiO3 doped with cobalt • Supports two phases • Resolution micro-meter, but feature size 10nm • Thin film not monolayer Fe Ka 1 Co Ka 1 Ti Ka 1 Ba Ka 1 EDS spectrum taken by Bin Liu VPD Group NUANCE Center

  10. Multiferroic Applications: Nanostructures • SEM images of 500 nm dots • 50% CoFe2O4 on silicon substrate VPD Group NUANCE Center

  11. Future Work • Use ICP-MS to further verify doped BaTiO3 composition • Use XPS to further verify composition of thin films • Optimize concentrations of sol-gels, dopants, and mixtures • Continue to pattern nano-structures using eBL • Test magnetic properties of structures using MFM • Test electrical properties of structures using PFM VPD Group NUANCE Center

  12. Results and Conclusions • CoFe2O4 – BaTiO3 mixtures: • X-ray powder diffraction suggests two separate phases mixed together • EDS also supports two separate phases • BaTiO3 with magnetic ions: • X-ray powder diffraction suggests single phase • Peak shift suggests change in lattice parameters • Peak to background intensity ratio change suggests defects increase with concentration Possible double phase multiferroic Possible single phase multiferroic VPD Group NUANCE Center

  13. Acknowledgements • Bin Liu • Prof. Dravid • Prof. Carsello • MRSEC and NSF • J. Wang et al. Science299 (2003) 1719. • R. Ramesh; N. Spaldin. Nature Materials 6 (2007) 23. • Tao Sun et al. Appl. Phys. Lett.89 (2006) 163117. • Nan C-W; Bichurin, M.I. et al. J. Appl. Phys.103 (2008). VPD Group NUANCE Center

  14. Si Substrate Dark Green: 10% Co Green: 1% Co Si Substrate Si Substrate ? Lime: 1% CoFe2O4 Green: 20% CoFe2O4 Dark Green and Indigo: 50% CoFe2O4 Si Substrate ? BTO <101> XRD thin film spectra • Thin films were too thin (10 nm – 50 nm) • Sample size was too small • Samples had too many disconnected grains VPD Group NUANCE Center

  15. BaTiO3 doped with magnetic ions: Co peaks <111> <200> <112> <211> <202> <220> <201> <210> VPD Group NUANCE Center

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