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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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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


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

non linear transmission line motivation
Non-linear Transmission Line Motivation

Shock wave generation

Voltage gain

Creation of harmonics

Soliton propagation

  • 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
proposed research
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
proposed material structure
Proposed Material Structure

Layer A: Ba0.5-xSrx+0.5TiO3

Layer B: Bax+0.5Sr0.5-xTiO3

transmission line study
Transmission Line Study
  • Minimum Device Specifications
    • Unity Voltage Gain
    • Sharpen Leading Edge of Pulse to 100ps
unproposed research
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
dielectric backgroud
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
material properties
Material Properties


: of or relating to crystalline substances having spontaneous electric polarization reversible by an electric field


Definition According to Mirriam-Webster

Non-linear Relationship Between Polarization and Electric Field

material properties1
Material Properties


  • 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
strain effects
Strain Effects





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

thickness effects
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


ferroelectric superlattices
Ferroelectric Superlattices

Layered Thin Film Materials Can Create Local Environments Unlike Bulk Environments

Thicker Films Can Create Strain Throughout the Sample


oxide growth by mbe
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
soluble substrates
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
current state of the art non linear transmission lines
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
varactor based non linear transmission lines
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

bulk ferroelectric lines
Bulk Ferroelectric Lines


Lines 2m Were Fabricated and Tested

Probes Were Placed at Different Locations Along the Line

Output Was Studied as a Function of Input

ferroelectric thin film transmission lines
Ferroelectric Thin Film Transmission Lines


  • 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
transmission line modeling
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
high level pseudo code analysis
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
ringing and filtering
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

intellectual property issues
Intellectual Property Issues

Freestanding Thin Films

Cold-welded Thin Films

Non-linear Transmission Line


[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.

ferroelectric superlattices for use in non linear transmission lines1

Ferroelectric Superlattices for Use in Non-linear Transmission Lines

Robert James Sleezer

Research Proposal Defense

16 December 2008