Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Targeted chemical pressure yields tuneable millimetre-wave dielectric


Epitaxial strain can unlock enhanced properties in oxide materials, but restricts substrate choice and maximum film thickness, above which lattice relaxation and property degradation occur. Here we employ a chemical alternative to epitaxial strain by providing targeted chemical pressure, distinct from random doping, to induce a ferroelectric instability with the strategic introduction of barium into today’s best millimetre-wave tuneable dielectric, the epitaxially strained 50-nm-thick n = 6 (SrTiO3)nSrO Ruddlesden–Popper dielectric grown on (110) DyScO3. The defect mitigating nature of (SrTiO3)nSrO results in unprecedented low loss at frequencies up to 125 GHz. No barium-containing Ruddlesden–Popper titanates are known, but the resulting atomically engineered superlattice material, (SrTiO3)nm(BaTiO3)mSrO, enables low-loss, tuneable dielectric properties to be achieved with lower epitaxial strain and a 200% improvement in the figure of merit at commercially relevant millimetre-wave frequencies. As tuneable dielectrics are key constituents of emerging millimetre-wave high-frequency devices in telecommunications, our findings could lead to higher performance adaptive and reconfigurable electronics at these frequencies.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: The inequivalence of local chemical and global epitaxial strain in (SrTiO3)n−1(BaTiO3)1SrO phases.
Fig. 2: Structural characterization of ~50-nm-thick epitaxial (SrTiO3)n−1(BaTiO3)1SrO films with n = 2–6 grown on (110) DyScO3 substrates.
Fig. 3: Emergence of ferroelectricity in (SrTiO3)n−1(BaTiO3)1SrO films grown on (110) DyScO3.
Fig. 4: In-plane dielectric constant (K11) of 100-nm n = 6 (SrTiO3)n−1(BaTiO3)1SrO film on (110) DyScO3, and its tuneability at room temperature and high frequency.

Data availability

Figure data, DFT files and additional information can be accessed on the NIST Public Data Repository via the following link:


  1. 1.

    Tagantsev, A. K., Sherman, V. O., Astafiev, K. F., Venkatesh, J. & Setter, N. Ferroelectric materials for microwave tunable applications. J. Electroceram. 11, 5–66 (2003).

    CAS  Google Scholar 

  2. 2.

    Bao, P., Jackson, T. J., Wang, X. & Lancaster, M. J. Barium strontium titanate thin film varactors for room temperature microwave device applications. J. Phys. D. 41, 063001 (2008).

    Google Scholar 

  3. 3.

    Gevorgian, S. Ferroelectrics in Microwave Devices, Circuits and Systems: Physics, Modeling, Fabrication and Measurements (Springer, 2009).

  4. 4.

    Subramanyam, G. et al. Challenges and opportunities for multi-functional oxide thin films for voltage tunable radio frequency/microwave components. J. Appl. Phys. 114, 191301 (2013).

    Google Scholar 

  5. 5.

    Meyers, C. J. G., Freeze, C. R., Stemmer, S. & York, R. A. (Ba,Sr)TiO3 tunable capacitors with RF commutation quality factors exceeding 6000. Appl. Phys. Lett. 109, 112902 (2016).

    Google Scholar 

  6. 6.

    Vorobiev, A., Rundqvist, P., Khamchane, K. & Gevorgian, S. Microwave loss mechanisms in Ba0.25Sr0.75TiO3 thin film varactors. J. Appl. Phys. 96, 4642–4649 (2004).

    CAS  Google Scholar 

  7. 7.

    Lee, C.-H. et al. Exploiting dimensionality and defect mitigation to create tunable microwave dielectrics. Nature 502, 532–536 (2013).

    CAS  Google Scholar 

  8. 8.

    Ruddlesden, S. N. & Popper, P. New compounds of the K2NIF4 type. Acta Crystallogr. 10, 538–539 (1957).

    CAS  Google Scholar 

  9. 9.

    Ruddlesden, S. N. & Popper, P. The compound Sr3Ti2O7 and its structure. Acta Crystallogr. 11, 54–55 (1958).

    CAS  Google Scholar 

  10. 10.

    Tilley, R. J. D. Correlation between dielectric constant and defect structure of non-stoichiometric solids. Nature 269, 229–231 (1977).

    CAS  Google Scholar 

  11. 11.

    Tilley, R. J. D. An electron microscope study of perovskite-related oxides in the Sr-Ti-O system. J. Solid State Chem. 21, 293–301 (1977).

    CAS  Google Scholar 

  12. 12.

    Knott, L. J., Cockroft, N. J. & Wright, J. C. Site-selective spectroscopy of erbium-doped SrTiO3, Sr2TiO4, and Sr3Ti2O7. Phys. Rev. B. 51, 5649–5658 (1995).

    CAS  Google Scholar 

  13. 13.

    Choi, K. J. et al. Enhancement of ferroelectricity in strained BaTiO3 thin films. Science 306, 1005–1009 (2004).

    CAS  Google Scholar 

  14. 14.

    Béa, H. et al. Evidence for room-temperature multiferroicity in a compound with a giant axial ratio. Phys. Rev. Lett. 102, 217603 (2009).

    Google Scholar 

  15. 15.

    Haislmaier, R. C. et al. Unleashing strain induced ferroelectricity in complex oxide thin films via precise stoichiometry control. Adv. Funct. Mater. 26, 7271–7279 (2016).

    CAS  Google Scholar 

  16. 16.

    Wei, Y. et al. A rhombohedral ferroelectric phase in epitaxially strained Hf0.5Zr0.5O2 thin films. Nat. Mater. 17, 1095–1100 (2018).

    CAS  Google Scholar 

  17. 17.

    Wood, C. E. C., Metze, G., Berry, J. & Eastman, L. F. Complex free-carrier profile synthesis by “atomic-plane” doping of MBE GaAs. J. Appl. Phys. 51, 383–387 (1980).

    CAS  Google Scholar 

  18. 18.

    Schubert, E. F. Delta doping of III–V compound semiconductors: Fundamentals and device applications. J. Vac. Sci. Technol. A 8, 2980–2996 (1990).

    CAS  Google Scholar 

  19. 19.

    Birol, T., Benedek, N. A. & Fennie, C. J. Interface control of emergent ferroic order in Ruddlesden–Popper Srn+1TinO3n+1. Phys. Rev. Lett. 107, 257602 (2011).

    Google Scholar 

  20. 20.

    Neaton, J. B. & Rabe, K. M. Theory of polarization enhancement in epitaxial BaTiO3/SrTiO3 superlattices. Appl. Phys. Lett. 82, 1586–1588 (2003).

    CAS  Google Scholar 

  21. 21.

    Tenne, D. A. et al. Probing nanoscale ferroelectricity by ultraviolet Raman spectroscopy. Science 313, 1614–1616 (2006).

    CAS  Google Scholar 

  22. 22.

    Bland, J. A. The crystal structure of barium orthotitanate, Ba2TiO4. Acta Crystallogr. 14, 875–881 (1961).

    CAS  Google Scholar 

  23. 23.

    Lee, S., Randall, C. A. & Liu, Z.-K. Modified phase diagram for the barium oxide–titanium dioxide system for the ferroelectric barium titanate. J. Am. Ceram. Soc. 90, 2589–2594 (2007).

    CAS  Google Scholar 

  24. 24.

    Kwestroo, W. & Paping, H. A. M. The systems BaO-SrO-TiO2, BaO-CaO-TiO2, and SrO-CaO-TiO2. J. Am. Ceram. Soc. 42, 292–299 (1959).

    CAS  Google Scholar 

  25. 25.

    Veličkov, B., Kahlenberg, V., Bertram, R. & Bernhagen, M. Crystal chemistry of GdScO3, DyScO3, SmScO3 and NdScO3. Z. Für. Krist 222, 466–473 (2007).

    Google Scholar 

  26. 26.

    Xi, X. X. et al. Oxide thin films for tunable microwave devices. J. Electroceram. 4, 393–405 (2000).

    CAS  Google Scholar 

  27. 27.

    Houzet, G., Burgnies, L., Velu, G., Carru, J.-C. & Lippens, D. Dispersion and loss of ferroelectric Ba0.5Sr0.5TiO3 thin films up to 110 GHz. Appl. Phys. Lett. 93, 053507 (2008).

    Google Scholar 

  28. 28.

    Gu, Z. et al. Resonant domain-wall-enhanced tunable microwave ferroelectrics. Nature 560, 622–627 (2018).

    CAS  Google Scholar 

  29. 29.

    Haeni, J. H., Theis, C. D. & Schlom, D. G. RHEED intensity oscillations for the stoichiometric growth of SrTiO3 thin films by reactive molecular beam epitaxy. J. Electroceram. 4, 385–391 (2000).

    CAS  Google Scholar 

  30. 30.

    Haislmaier, R. C., Stone, G., Alem, N. & Engel-Herbert, R. Creating Ruddlesden–Popper phases by hybrid molecular beam epitaxy. Appl. Phys. Lett. 109, 043102 (2016).

    Google Scholar 

  31. 31.

    Gevorgian, S. S., Martinsson, T., Linner, P. L. J. & Kollberg, E. L. CAD models for multilayered substrate interdigital capacitors. IEEE Trans. Microw. Theory Tech. 44, 896–904 (1996).

    Google Scholar 

  32. 32.

    Kidner, N. J., Homrighaus, Z. J., Mason, T. O. & Garboczi, E. J. Modeling interdigital electrode structures for the dielectric characterization of electroceramic thin films. Thin Solid Films 496, 539–545 (2006).

    CAS  Google Scholar 

  33. 33.

    Kresse, G. & Furthmüller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B. 54, 11169–11186 (1996).

    CAS  Google Scholar 

  34. 34.

    Kresse, G. & Joubert, D. From ultrasoft pseudopotentials to the projector augmented-wave method. Phys. Rev. B. 59, 1758–1775 (1999).

    CAS  Google Scholar 

  35. 35.

    Perdew, J. P. et al. Restoring the density-gradient expansion for exchange in solids and surfaces. Phys. Rev. Lett. 100, 136406–136406 (2008).

    Google Scholar 

  36. 36.

    Monkhorst, H. J. & Pack, J. D. Special points for Brillouin-zone integrations. Phys. Rev. B. 13, 5188–5192 (1976).

    Google Scholar 

  37. 37.

    Togo, A. & Tanaka, I. First principles phonon calculations in materials science. Scr. Mater. 108, 1–5 (2015).

    CAS  Google Scholar 

  38. 38.

    Togo, A. & Tanaka, I. Evolution of crystal structures in metallic elements. Phys. Rev. B. 87, 184104 (2013).

    Google Scholar 

  39. 39.

    Stokes, H. T., Hatch, D. M. & Campbell, B. J. ISOTROPY Software Suite (Brigham Young University, 2015);

  40. 40.

    Momma, K. & Izumi, F. VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data. J. Appl. Crystallogr. 44, 1272–1276 (2011).

    CAS  Google Scholar 

  41. 41.

    Marks, R. B. A multiline method of network analyzer calibration. IEEE Trans. Microw. Theory Tech. 39, 1205–1215 (1991).

    Google Scholar 

  42. 42.

    Williams, D. F., Wang, J. C. M. & Arz, U. An optimal vector-network analyzer calibration algorithm. IEEE Trans. Microw. Theory Tech. 51, 2391–2401 (2003).

    Google Scholar 

  43. 43.

    Williams, D. F., Marks, R. B. & Davidson, A. Comparison of on-wafer calibrations. In Proc. 38th Automatic RF Techniques Group Conference Dig 68–81 (IEEE, 1991).

  44. 44.

    Orloff, N. D. et al. A compact variable-temperature broadband series-resistor calibration. IEEE Trans. Microw. Theory Tech. 59, 188–195 (2011).

    Google Scholar 

Download references


The synthesis, characterization and theoretical work at Cornell was supported by the US Department of Energy, Office of Basic Sciences, Division of Materials Sciences and Engineering (Award no. DE-SC0002334). Sample preparation was in part facilitated by the Cornell NanoScale Facility, a member of the National Nanotechnology Coordinated Infrastructure (NNCI), which is supported by the National Science Foundation (grant no. NNCI-1542081). Ferroelectric and dielectric measurements with temperature were conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. Infrared and terahertz studies were supported by the Czech Science Foundation (project no. 18–09265S) and by the MŠMT (project no. SOLID21-CZ.02.1.01/0.0/0.0/16 019/0000760). This work made use of Cornell Center for Materials Research Shared Facilities, which are supported through the NSF MRSEC program (no. DMR-1719875). Certain commercial equipment, instruments or materials are identified in this article to specify the experimental procedure adequately. Usage of commercial products herein is for information only; it does not imply recommendation or endorsement by NIST, and it is not intended to imply that the materials or equipment identified are necessarily the best available for the purpose.

Author information




N.M.D. and J.Z. synthesized the samples under the supervision of D.G.S. N.M.D. performed the ferroelectric and low frequency dielectric measurements versus temperature. G.H.O. performed the DFT calculations under the supervision of C.J.F. M.E.H. performed STEM measurements under the supervision of D.A.M. Millimetre-wave devices were fabricated and measured by E.J.M., A.M.H., X.L. and J.A.D. under the supervision of C.J.L., J.C.B. and N.D.O. R.U. and S.G. supplied the DyScO3 substrates. V.G. and C.K. performed the infrared and terahertz measurements under the supervision of S.K. N.M.D, D.G.S, E.J.M., A.M.H., N.D.O., G.H.O and M.E.H. wrote the manuscript. All authors discussed results and commented on the manuscript. The study was conceived and guided by D.G.S.

Corresponding author

Correspondence to Darrell G. Schlom.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Discussion, Figs. 1–10, and Refs. 1–7.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Dawley, N.M., Marksz, E.J., Hagerstrom, A.M. et al. Targeted chemical pressure yields tuneable millimetre-wave dielectric. Nat. Mater. 19, 176–181 (2020).

Download citation

Further reading


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing