Ferroelectric polarisation control in thin films via growth conditions

Session

Stream 1: EMAG - Functional Materials

Authors

Dr Aaron Naden (4), Dr Christian Weymann (3), Dr Salia Cherifi-Hertel (1), Dr Celine Lichtensteiger (3), Dr Iaroslav Gaponenko (3), Dr Stephanie Fernandez (3, 5), Dr Liv Dedon (2, 6), Prof Lane Martin (2), Prof Jean-Marc Triscone (3), Prof Patrycja Paruch (3)

Affiliations

1. CNRS
2. University of California at Berkeley
3. University of Geneva
4. University of St Andrews
5. CERN
6. University of Massachusetts

Keywords

Functional Semiconductor and Oxide Materials, Microscopy of Interfaces and Heterostructures, High Resolution Chemical and Structural Analysis

Abstract text

Ferroelectric materials have a myriad of applications such as in microelectromechanical systems (MEMS)¹ and non-volatile random access memories² due to their switchable electrical polarisation and piezoelectric properties. For such device applications, deterministic control of the intrinsic polarisation state of the ferroelectric thin film is of paramount importance since an initial defined monodomain state (where the polarisation is uniformly oriented) is often desirable. Realising an intrinsic, as-grown, monodomain state is therefore advantageous since it would eliminate preliminary poling steps which can be detrimental due to modification of the surface chemistry of the films.³ Key factors dictating the intrinsic polarisation states in epitaxial films include electrostatic boundary conditions and epitaxial strain which can be readily altered by, for example, the choice of bottom electrode and/or substrate,^4,5 film thickness⁵ or changes to the chemical environment.⁶

 

Here, we report deterministic control of the intrinsic polarisation of epitaxial PbTiO₃,⁷ a canonical ferroelectric that provides an ideal model system owing to its versatility, the wealth of literature available and its inclusion in the Pb(Zr_­x,Ti_1-x)O₃-based solid solutions which are widely employed in commercial devices.⁸ As a function of increasing growth temperature, we establish a transition from monodomain “up” through to polydomain and finally monodomain “down”. A combination of energy dispersive X-ray spectroscopy (EDX) and scanning transmission electron microscopy (STEM) reveals variations in stoichiometry and out-of-plane strain through the film thicknesses resulting in polarisation gradients which we directly visualise via atomic resolution STEM. These highly local observations are complemented by larger scale measurements by means of X-ray diffraction, Rutherford backscattering spectroscopy and piezoresponse force microscopy. The detailed characterisation presented here enables a comprehensive understanding of the origin of intrinsic polarisation states in these ferroelectric thin films. Moreover, adjustment of growth temperature provides a particularly simple method for control of polarisation, providing an additional tuning parameter for domain engineering and the potential realisation of more complex films with unusual polarisation textures such as vortex and skyrmion-like topologies.

References

¹ S. Trolier-Mckinstry and P. Muralt, J. Electroceramics 12, 7 (2004).

² J.F. Scott and C.A. Paz De Araujo, Science 246, 1400 (1989).

³ N. Domingo, I. Gaponenko, K. Cordero-Edwards, N. Stucki, V. Pérez-Dieste, C. Escudero, E. Pach, A. Verdaguer, and P. Paruch, Nanoscale 11, 17920 (2019).

⁴ H. Lu, X. Liu, J.D. Burton, C.W. Bark, Y. Wang, Y. Zhang, D.J. Kim, A. Stamm, P. Lukashev, D.A. Felker, C.M. Folkman, P. Gao, M.S. Rzchowski, X.Q. Pan, C.B. Eom, E.Y. Tsymbal, and A. Gruverman, Adv. Mater. 24, 1209 (2012).

⁵ D.G. Schlom, L.-Q. Chen, C.-B. Eom, K.M. Rabe, S.K. Streiffer, and J.-M. Triscone, Annu. Rev. Mater. Res. 37, 589 (2007).

⁶ R. V. Wang, D.D. Fong, F. Jiang, M.J. Highland, P.H. Fuoss, C. Thompson, A.M. Kolpak, J.A. Eastman, S.K. Streiffer, A.M. Rappe, and G.B. Stephenson, Phys. Rev. Lett. 102, 047601 (2009).

⁷ C. Weymann, C. Lichtensteiger, S. Fernandez-Peña, A.B. Naden, L.R. Dedon, L.W. Martin, J. Triscone, and P. Paruch, Adv. Electron. Mater. 6, 2000852 (2020).

⁸ G.H. Haertling, J. Am. Ceram. Soc. 82, 797 (1999).