Darrell G. Schlom 1 2
Using epitaxy and the misfit strain imposed by an underlying substrate, it is possible to strain oxide thin films to percent levels—far beyond where they would crack in bulk. Under such strains, the properties of oxides can be dramatically altered. For example, materials that are not ferroelectric or ferromagnetic in their unstrained state can be transmuted into ferroelectrics,1,2 ferromagnets, or materials that are both at the same time.3 Strain can also be used to improve oxide photocatalytic materials,4 ferroelectrics,5 and tunable microwave dielectrics.6 Our results show that for oxide thin films, strain is a viable alternative to the traditional method of chemical substitutions for selecting between alternate ground states. This work was performed in collaboration with the coauthors listed in the references below.
1. J.H. Haeni, P. Irvin, W. Chang, R. Uecker, P. Reiche, Y.L. Li, S. Choudhury, W. Tian, M.E. Hawley, B. Craigo, A.K. Tagantsev, X.Q. Pan, S.K. Streiffer, L.Q. Chen, S.W. Kirchoefer, J. Levy, and D.G. Schlom, “Room-Temperature Ferroelectricity in Strained SrTiO3,” Nature430 (2004) 758-761.
2. M.P. Warusawithana, C. Cen, C.R. Sleasman, J.C. Woicik, Y.L. Li, L.F. Kourkoutis, J.A. Klug, H. Li, P. Ryan, L-P. Wang, M. Bedzyk, D.A. Muller, L.Q. Chen, J. Levy, and D.G. Schlom, “A Ferroelectric Oxide Made Directly on Silicon,” Science324 (2009) 367-370.
3. J.H. Lee, L. Fang, E. Vlahos, X. Ke, Y.W. Jung, L.F. Kourkoutis, J-W. Kim, P.J. Ryan, T. Heeg, M. Roeckerath, V. Goian, M. Bernhagen, R. Uecker, P.C. Hammel, K.M. Rabe, S. Kamba, J. Schubert, J.W. Freeland, D.A. Muller, C.J. Fennie, P. Schiffer, V. Gopalan, E. Johnston-Halperin, and D.G. Schlom, “A Strong Ferroelectric Ferromagnet Created by means of Spin-Lattice Coupling,” Nature466 (2010) 954-958.
4. C.M. Brooks, R.F. Berger, D. Chvostova, V. Trepakov, N.J. Podraza, L.F. Kourkoutis, T. Heeg, M. Bernhagen, R. Uecker, J. Schubert, D.A. Muller, A. Dejneka, C.J. Fennie, J.B. Neaton, and D.G. Schlom, “Manipulating the Band Structure of SrTiO3 via Strain-Controlled Ferroelectric Phase Transitions,” (unpublished).
5. K.J. Choi, M.D. 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,” Science306 (2004) 1005-1009.
6. 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.-S. 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,” (unpublished).