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Ferroelectric Superlattices for Use in Non-linear Transmission Lines

Ferroelectric Superlattices for Use in Non-linear Transmission Lines. Robert James Sleezer Research Proposal Defense 16 December 2008. Acknowledgements. Gregg Salamo , Advisor Jerzy Krasinski , Masters Advisor and Committee Member Laurent Bellaiche , Committee Member

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Ferroelectric Superlattices for Use in Non-linear Transmission Lines

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  1. Ferroelectric Superlattices for Use in Non-linear Transmission Lines Robert James Sleezer Research Proposal Defense 16 December 2008

  2. Acknowledgements Gregg Salamo, Advisor JerzyKrasinski, Masters Advisor and Committee Member Laurent Bellaiche, Committee Member Jacques Chakhalian, Committee Member Ken Vickers, Committee Member Morgan Ware, Mentor VasylKunets, Mentor Zhao-QuanZeng, Mentor National Science Foundation G-K12 Progam MRI #0421099 (Red Diamond) and MRI #072265 (Star of Arkansas) from the National Science Foundation

  3. Non-linear Transmission Line Motivation Shock wave generation Voltage gain Creation of harmonics Soliton propagation

  4. Overview • Proposed Research • The Big Picture • Expected Deliverables • Materials Background • Ferroelectric Material Properties • Strain and Thickness Effects • Material Growth • Prior Non-linear Transmission Line Results • Discrete Lines • Bulk Results • Thin Film Expectations and Results • Transmission Line Model • Finite Element Model • Preliminary Results • Intellectual Property Expected to Result From Research • Research Plan

  5. Proposed Research • The Big Picture • Expected Deliverables • Material Research • Property Variation With Strain • Dielectric Constant • Loss Tangent • Curie Temperature • Hysteresis Curve • Comparison to Previously Developed Model • Transmission Line Behavior • Rise Time as a Function of Propagation Distance • Gain as a Function of Propagation Distance • Comparison to Model • Unproposed Research

  6. The Big Picture

  7. The Big Picture

  8. Proposed Material Structure Layer A: Ba0.5-xSrx+0.5TiO3 Layer B: Bax+0.5Sr0.5-xTiO3

  9. A Study of Material Property Variation With Strain

  10. Transmission Line Study • Minimum Device Specifications • Unity Voltage Gain • Sharpen Leading Edge of Pulse to 100ps

  11. Unproposed Research • Extensions • Modification of Transmission Line Structure • Creation of Artificial Unit Cell • Modification of Structure for Optimal Voltage Gain • Study of Thickness Contribution Above Critical Thickness • Future Directions • Study of Thickness Below Critical Thickness • Use of Additional Materials

  12. Dielectric Backgroud • Ferroelectric Material Properties • Hysteresis • Dielectric Constant • Curie Temperature • Strain and Thickness Effects • Strain and Ferroelectric Films • Thin Film Effects • Superlattices • Material Growth • Shuttered RHEED MBE • Soluble Substrates

  13. Material Properties P : of or relating to crystalline substances having spontaneous electric polarization reversible by an electric field E Definition According to Mirriam-Webster Non-linear Relationship Between Polarization and Electric Field

  14. Material Properties [1-3] • Curie Temperature • Temperature of Phase Change • Below Tc the Material is Ferroelectric • Above Tc the Material is Paraelectric • The Dielectric Constant, a Function of Temperature, Peaks at Tc

  15. Strain Effects orthorhombic rhombohedral tetragonal [4,5] Strain Imposed by Lattice Mismatch With Substrate or Neighboring Layers Changes in Tc and In Turn Phase Strain May Effect Tc in a Thin Film Ferroelectric

  16. Thickness Effects Satellites in the diffraction pattern of PTO are an indication of ferroelectric stripe domains. The sample with four unit cells remains ferroelectric through at least 644K, the three unit cell sample looses it’s ferroelectricity between 463K and 549K, and the thinner samples remain paraelectric at all temperatures. An Atom in an Ultrathin Film Does Not Experience the Same Environment as an Atom in Bulk Material Slightly Thicker Films Also Show Material Property Variation [6,7]

  17. Ferroelectric Superlattices Layered Thin Film Materials Can Create Local Environments Unlike Bulk Environments Thicker Films Can Create Strain Throughout the Sample [8]

  18. Oxide Growth By MBE TiO2 Surface SrO Surface • Shuttered RHEED Growth • Beam Flux Calibration Done With Shuttered RHEED • Requires Extra Substrate • Time Consuming • Addition of Quartz Microbalance Planned

  19. Soluble Substrates • Use of Soluble Substrates Allows • Freestanding Thin Films • Eliminate Strain Contribution of Substrate • Study the Backside of the Material • Metal Contact to Top and Bottom of Thin Film • Novel Devices • Substrate of Choice is LiF • Good Lattice Match • Moderately Soluble • Relatively Inexpensive • Surface Quality May Be a Problem

  20. Current State of the Art Non-linear Transmission Lines • Discrete Lines • Varactor Based • Ferroelectric Capacitor Based • Disadvantages • Large • Limited by Unit Cell • Bulk Lines • Extremely Large • High Voltage • Thin Film Lines • Previous Results • Expectations

  21. Varactor Based Non-linear Transmission Lines tr = 80ns tr = 40ns [9, 10] Transmission Line Constructed From Discrete Inductors and Varactors Shock Wave With Ringing Related to Unit Cell Resonant Frequency is Developed

  22. Bulk Ferroelectric Lines [11] Lines 2m Were Fabricated and Tested Probes Were Placed at Different Locations Along the Line Output Was Studied as a Function of Input

  23. Ferroelectric Thin Film Transmission Lines [12] • Coplanar Transmission Lines Fabricated on BST • 400 nm of BST on LaAlO3 • 1.0um Thick Silver Conductors • Center Conductor Width of 53um • Line Length of 10.52mm • The Third Harmonic Increased with Increasing Input Power • Only Known Study Using Thin Film Ferroelectric Transmission Lines

  24. Transmission Line Modeling • Finite Element Model • Unit Cell • Derivation of Differential Equation • Implementation • Preliminary Results • Initial Parameters • Pulse Propagation • Ringing and Filtering • Rise Time and Gain Analysis

  25. Model Unit Cell

  26. Differential Equation Resulting From Unit Cell

  27. High Level Pseudo Code Analysis • Nt = t/dt • Nn = x/dx • Loop on Nt • Loop on Nn • Solve Differential Equation • End • End • O(Nt*Nn) • Nt is about 10^7 and Nn is about 10^5

  28. Simulation Parameters for Preliminary Results

  29. Ringing and Filtering Unfiltered Simulation Results Show Significant Ringing at Unit Cell Resonant Frequency Application of a Band Reject Filter Removes Unwanted Ringing Smaller Unit Cells Have Higher Frequency Ringing Adjustments to Rc to Account For Frequency Dependant Loss Tangent

  30. Intellectual Property Issues Freestanding Thin Films Cold-welded Thin Films Non-linear Transmission Line

  31. Research Plan

  32. References [1] E. Fatuzzo and W. J. Merz, Ferroelectricity. New York, New York: John Wiley & Sons Inc., 1967. [2] C. Kittel, Introduction to Solid State Physics, Eigth Edition ed. Hoboken, New Jersy: John Wiley & Sons, 2005. [3] K. J. Choi, M. Biegalski, Y. L. Li, A. Sharan, J. Schubert, R. Uecker, P. Reiche, Y. B. Chen, X. Q. Pan, V. Gopalan, L. Q. Chen, D. G. Schlom, and C. B. Eom, "Enhancement of Ferroelectricity in Strained BaTiO3 Thin Films," Science, vol. 306, pp. 1005-1009, November 5, 2004 2004. [4] P. Townsend, "Si/SiGe Semiconductor Physics Research at the University of Cambridge." vol. 2008 Cambridge, UK: Si/SiGe Semiconductor Physics Research at the University of Cambridge, Cavendish Laboratory, 2004. [5] N. A. Pertsev, A. G. Zembilgotov, and A. K. Tagantsev, "Effect of Mechanical Boundary Conditions on Phase Diagrams of Epitaxial Ferroelectric Thin Films," Physical Review Letters, vol. 80, p. 1988, 1998. [6] D. D. Fong, G. B. Stephenson, S. K. Streiffer, J. A. Eastman, O. Auciello, P. H. Fuoss, and C. Thompson, "Ferroelectricity in Ultrathin Perovskite Films," Science, vol. 304, pp. 1650-1653, June 11, 2004 2004. [7] C. Basceri, S. K. Streiffer, A. I. Kingon, and R. Waser, "The dielectric response as a function of temperature and film thickness of fiber-textured (Ba,Sr)TiO[sub 3] thin films grown by chemical vapor deposition," Journal of Applied Physics, vol. 82, pp. 2497-2504, 1997. [8] H. N. Lee, H. M. Christen, M. F. Chisholm, C. M. Rouleau, and D. H. Lowndes, "Strong polarization enhancement in asymmetric three-component ferroelectric superlattices," Nature, vol. 433, pp. 395-399, 2005. [9] C. R. Wilson, M. M. Turner, and P. W. Smith, "Pulse sharpening in a uniform LC ladder network containing nonlinear ferroelectric capacitors," in Power Modulator Symposium, 1990., IEEE Conference Record of the 1990 Nineteenth, 1990, pp. 204-207. [10] K. Lonngren, D. Landt, C. Burde, and J. Kolosick, "Observation of shocks on a nonlinear dispersive transmission line," Circuits and Systems, IEEE Transactions on, vol. 22, pp. 376-378, 1975. [11] G. Branch and P. W. Smith, "ELECTROMAGNETIC SHOCK-WAVES IN DISTRIBUTED DELAY LINES WITH NONLINEAR DIELECTRICS," in Power Modulator Symposium, 1992. Conference Record of the 1992 Twentieth, 1992, p. 355. [12] J. C. Booth, R. H. Ono, I. Takeuchi, and K.-S. Chang, "Microwave frequency tuning and harmonic generation in ferroelectric thin film transmission lines," Applied Physics Letters, vol. 81, pp. 718-720, 2002.

  33. Ferroelectric Superlattices for Use in Non-linear Transmission Lines Robert James Sleezer Research Proposal Defense 16 December 2008

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