Darrell G. Schlom

Department of Materials Science and Engineering Cornell University, Ithaca, NY, 14853-1501  U.S.A.
Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY, 14853-1501  U.S.A.
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Today’s tunable dielectric with the highest figure of merit at room temperature is strained films of (SrTiO3)6SrO.  The low loss at frequencies up to 125 GHz comes from the defect mitigating nature of the (SrTiO3)nSrO Ruddlesden-Popper structure; the tunability arises from imposing strain to induce a ferroelectric instability.  Unfortunately the necessity for strain limits the film thickness to around 50 nm, which reduces the device tuning that can be achieved.  In this talk I will describe a chemical alternative to strain to induce a ferroelectric instability—the introduction of barium into this Ruddlesden-Popper titanate.  No barium-containing Ruddlesden-Popper titanates are known, but this atomically engineered superlattice material can be made thicker and we demonstrate a 300% improvement in the figure of merit of this this new (SrTiO3)nm(BaTiO3)mSrO tunable dielectric. 

This work was performed in collaboration with the coauthors listed in the references below.


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C.H. Lee, N.D. Orloff, T. Birol, Y. Zhu, V. Goian, E. Rocas, R. Haislmaier, E. Vlahos, J.A. Mundy, L.F. Kourkoutis, Y. Nie, M.D. Biegalski, J. Zhang, M. Bernhagen, N.A. Benedek, Y. Kim, J.D. Brock, R. Uecker, X.X. Xi, V. Gopalan, D. Nuzhnyy, S. Kamba, D.A. Muller, I. Takeuchi, J.C. Booth, C.J. Fennie, and D.G. Schlom, "Exploiting Dimensionality and Defect Mitigation to Create Tunable Microwave Dielectrics," Nature 502 (2013) 532–536. https://doi.org/10.1038/nature12582

C.H. Lee, V. Skoromets, M.D. Biegalski, S. Lei, R. Haislmaier, M. Bernhagen, R. Uecker, X.X. Xi, V. Gopalan, X. Martí, S. Kamba, P. Kužel, and D.G. Schlom, "Effect of Stoichiometry on the Dielectric Properties and Soft Mode Behavior of Strained Epitaxial SrTiO3 Thin Films on DyScO3 Substrates," Applied Physics Letters 102 (2013) 082905.

https://doi.org/10.1063/1.4793649 Y.F. Nie, Y. Zhu, C.-H. Lee, L.F. Kourkoutis, J.A. Mundy, J. Junquera, P. Ghosez, D.J. Baek, S. Sung, X.X. Xi, K.M. Shen, D.A. Muller, and D.G. Schlom, "Atomically Precise Interfaces from Non-Stoichiometric Deposition," Nature Communications 5 (2014) 4530. https://doi.org/10.1038/ncomms5530

V. Goian, S. Kamba, N. Orloff, T. Birol, C.H. Lee, D. Nuzhnyy, J.C. Booth, M. Bernhagen, R. Uecker, and D.G. Schlom, "Influence of the Central Mode and Soft Phonon on the Microwave Dielectric Loss near the Strain-Induced Ferroelectric Phase Transitions in Srn+1TinO3n+1," Physical Review B 90 (2014) 174105. https://doi.org/10.1103/PhysRevB.90.174105

A.M. Hagerstrom, X. Lu, N.M. Dawley, H. Nair, J. Mateu, R. Horansky, C.A.E. Little, J.C. Booth, C.J. Long, D.G. Schlom, and N.D. Orloff, "Sub-nanosecond Tuning of Microwave Resonators Fabricated on Ruddlesden-Popper Dielectric Thin Films," Advanced Materials Technologies (in press).

N.M. Dawley, E.J. Marksz, A.M. Hagerstrom, M.E. Holtz, G.H. Olsen, J. Zhang, C.J. Long, J.C. Booth, C.J. Fennie, D.A. Muller, N.D. Orloff, and D.G. Schlom, "Applying Chemistry to Make Today's Best Tunable Millimeter Wave Dielectric even Better" (unpublished).