1 / 16

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. Outline. What are multiferroics? Summer work

romeo
Télécharger la présentation

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

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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. Outline • What are multiferroics? • Summer work • What is eBL? • Results so far… • Future work Research questions • Can we create synthetic multiferroics on the nano scale in which ferroelectric and ferromagnetic properties are connected at room temperature? • How do multiferroic properties change when patterned on the nanoscale? J. Wang et al. Science299 (2003)1721. VPD Group NUANCE Center

  3. Multiferroic ceramics Diamagnetic • Materials with: • Coupled electric, magnetic and structural order parameters • Simultaneous ferroic properties (i.e. ferroelectric, ferromagnetic, or ferroelastic). • Conflict between ferroelectric and ferromagnetic crystal structure • Future applications: • Data storage, communications, sensors, resonators, and power control devices. Ferromagnetic Anti-Ferromagnetic “Weak” or canted Ferromagnetic J. Wang et al. Science299 (2003)1721. Nan C-W; Bichurin, M.I. et al. J. Appl. Phys.103 (2008). VPD Group NUANCE Center

  4. Multiferroics cont… • Naturally occurring single phase multiferroics: BiFeO3, hexagonal HoMnO3 • BiFeO3 is ferroelectric and anti- ferromagnetic at room temperature • Possible synthetic multiferroics: • Combination of two phases: • Ferroelectric BaTiO3 and ferromagnetic Fe3O4 or CoFe2O4 combined in hetero- structures or epitaxial thin films • Magnetic phase dispersed in a ferroelectric • Dope BaTiO3 with magnetic Mn, Fe, or Co ion O2- Mn3+ Ho3+ J. Wang et al. Science299 (2003) 1719. VPD Group NUANCE Center

  5. Summer Work • Mix CoFe2O4 and BaTiO3 sol-gels in ratios • Make powder samples and thin films to find out phase content using X-ray diffraction • Make nano-dots using eBL and find properties • Dope BaTiO3 with magnetic Mn, Fe, or Co ion • Make powder samples and thin films to find out phase content using X-ray diffraction • Make nano-dots using eBL and find properties VPD Group NUANCE Center

  6. “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

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

  8. XRD thin film: CoFe2O4 mixtures Si Substrate Si Substrate ? Lime: 1% CoFe2O4 Green: 20% CoFe2O4 Dark Green and Indigo: 50% CoFe2O4 VPD Group NUANCE Center

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

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

  11. XRD thin film: BaTiO3 doped with Co ions Si Substrate Dark Green: 10% Co Green: 1% Co Si Substrate ? BTO <101> VPD Group NUANCE Center

  12. XRD Results • CoFe2O4 mixtures: • Peaks are from primarily CoFe2O4 and BaTiO3 spectra, which suggests there are two separate phases mixed together • Will use EDS to verify two separate phases • Possible double-phase multiferroic • BaTiO3 with magnetic ions: • Peaks are all from BaTiO3 spectrum • Peaks shift with dopant concentration indicating some change in lattice constants • Suggests full incorporation of magnetic ions into the BaTiO3 crystal lattice • Possible singe phase multiferroic VPD Group NUANCE Center

  13. Nanodots • 50% CoFe2O4 on silicon substrate • 500 nm dots VPD Group NUANCE Center

  14. Future Work • In the next two weeks: • Pattern SrTiO2 substrate with dots of CoFe2O4 sol-gel mixtures • Look for epitaxial growth of single crystal dots • Investigate properties of nano-dots using PFM • Make a sol-gel combining CoFe2O4 and BaTiO3 sources in a single sample • Find XRD powder spectra • Finish taking XRD powder spectra for CoFe2O4 mixtures • … and beyond • Use ICP to verify doped BaTiO3 composition • Use XPS to verify composition of thin films • Continue to pattern nano-structures using eBL and test magnetic and electrical properties VPD Group NUANCE Center

  15. Acknowledgements • Bin Liu • Saranya • Prof. Dravid • Prof. Carsello VPD Group NUANCE Center

More Related