Oxygen Vacancy Injection as a Pathway to Enhancing Electromechanical Response in Ferroelectrics

KP Kelley and AN Morozovska and EA Eliseev and V Sharma and DE Yilmaz and ACT van Duin and P Ganesh and A Borisevich and S Jesse and P Maksymovych and N Balke and SV Kalinin and RK Vasudevan, ADVANCED MATERIALS, 34, 2106426 (2022).

DOI: 10.1002/adma.202106426

Since their discovery in late 1940s, perovskite ferroelectric materials have become one of the central objects of condensed matter physics and materials science due to the broad spectrum of functional behaviors they exhibit, including electro-optical phenomena and strong electromechanical coupling. In such disordered materials, the static properties of defects such as oxygen vacancies are well explored but the dynamic effects are less understood. In this work, the first observation of enhanced electromechanical response in BaTiO3 thin films is reported driven via dynamic local oxygen vacancy control in piezoresponse force microscopy (PFM). A persistence in peizoelectricity past the bulk Curie temperature and an enhanced electromechanical response due to a created internal electric field that further enhances the intrinsic electrostriction are explicitly demonstrated. The findings are supported by a series of temperature dependent band excitation PFM in ultrahigh vacuum and a combination of modeling techniques including finite element modeling, reactive force field, and density functional theory. This study shows the pivotal role that dynamics of vacancies in complex oxides can play in determining functional properties and thus provides a new route toward- achieving enhanced ferroic response with higher functional temperature windows in ferroelectrics and other ferroic materials.

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