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Synthesis of defect-mitigating tunable dielectric materials by MBE

C. H. Lee 1,2,  N. D. Orloff 3,4,  T. Birol 5,  Y. Zhu 5,  V. Goian 6,  R. Haislmaier 2,  E. Vlahos 2,  J. A. Mundy 5,  Y. Nie 5,  M. D. Biegalski 7,  J. Zhang 1,  M. Bernhagen 8,  N. A. Benedek 9,  Y. Kim 5,  J. D. Brock 5,  R. Uecker 8,  X. X. Xi 10,  L. F. Kourkoutis 5,11,  V. Gopalan 2,  D. Nuzhnyy 6,  S. Kamba 6,  D. A. Muller 5,11,  I. Takeuchi 12,  J. C. Booth 3,  C. J. Fennie 5,  Darrell G. Schlom 1,11

1. Cornell University, Department of Materials Science and Engineering, Ithaca, NY 14853-1501, United States
2. Department of Materials Science and Engineering, Pennsylvania State University, Pittsburgh, PA 15131, United States
3. National Institute of Standards and Technology (NIST), 100 Bureau Drive, MS-8362, Gaithersburg, Maryland 20899, United States
4. Department of Physics, University of Maryland, Washington, DC 20742, United States
5. School of Applied and Engineering Physics, Cornell University, Washington, DC 20037, United States
6. Czech Academy of Sciences, Institute of Physics, Na Slovance 2, Prague 182-21, Czech Republic
7. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Washington, DC 20024, United States
8. Leibniz Institute for Crystal Growth (IKZ), Max-Born-Str 2, Berlin 12489, Germany
9. Materials Science and Engineering Program, The University of Texas at Austin, Austin, TX 78712, United States
10. Temple University, Department of Physics, Philadelphia 19122, United States
11. Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY 14853, United States
12. Department of Materials Science and Engineering, University of Maryland, Washington, DC 20742, United States

Abstract

The miniaturization and integration of frequency-agile microwave circuits—electronically-tunable filters, resonators, phase shifters and more—with microelectronics offers tantalizing device possibilities, yet requires thin films whose dielectric constant at GHz frequencies can be tuned by applying a quasi-static electric field.  Appropriate systems, e.g., BaxSr1–xTiO3, have a paraelectric-to-ferroelectric transition just below ambient temperature, providing high tunability.  Unfortunately such films suffer significant losses arising from defects.  Recognizing that progress is stymied by dielectric loss, we start with a system with exceptionally low loss—Srn+1TinO3n+1 phases—where (SrO)2 crystallographic shear planes provide an alternative to point defect formation for accommodating non-stoichiometry.  We report the experimental realization of a highly tunable ground state arising from the emergence of a local ferroelectric instability in biaxially strained Srn+1TinO3n+1 phases with n ≥ 3 at frequencies up to 120 GHz.  In contrast to traditional methods of modifying ferroelectrics—doping or strain—in this rather unique system increasing the separation between the (SrO)2 planes bolsters the local ferroelectric instability.  This new control parameter, n, can be exploited to achieve a figure of merit at room temperature that surpasses all known tunable microwave dielectrics.

 

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Presentation: Oral at 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17, General Session 10, by Darrell G. Schlom
See On-line Journal of 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17

Submitted: 2013-06-08 17:07
Revised:   2013-07-23 12:04