Coexistence of polarization and ionic electromigration effects in the memristive response of ferroelectric oxides

C. FERREYRA; M. RENGIFO; JOSÉ SÁNCHEZ, MARÍA; A. EVERHARDT; B NOHEDA; D RUBI

Virtual

Congreso; European Materials Research Society Meeting; 2022

Memristors are metal/insulator/metal devices with high potential to be implemented as a newgeneration of non-volatile memories and novel neuromorphic computing devices. Thesestructures have the property of changing their resistance between different non-volatile states upon the application of external electrical stimuli, a process called resistive switching (RS). Physical mechanisms of RS are usually associated with the electromigration of defects, such as oxygen vacancies (OV), either by the creation/disruption of conductive nanofilaments or by the modulation of the height of Schottky barriers formed at metal/insulator interfaces. When the insulating oxide is ferroelectric, the resistive change at Schottky interfaces could be associated to the switching of the direction of the ferroelectric polarization- a process of electronic nature [1]-. Thus ferroelectric memristors usually present a faster and more reliable response than non-ferroelectric ones, which in general require from the electromigration of defects.In this work [2] we study the memristive response of PZT and BaTiO3-based ferroelectric memristors. We find in both cases that RS is related to two competing effects acting on metal/ferroelectric Schottky interfaces: the switching of the ferroelectric polarization and OV electromigration. We propose that both effects are entangled, being the latter mainly controlled by the depolarizing field arising from an incomplete screening of ferroelectric bounded charges. We simulate the experimental response with a modified version of the VEOV model [3] that accounts for the presence of ferroelectricity and satisfactorily reproduces several non-trivial aspects of the experimental response. Finally, we show that these systems display coexisting non-volatile and volatile memristive response, an issue that could be useful for the development of neuromorphic devices.[1] P. W. M. Blom, R. M. Wolf, J. F. M. Cillessen, and M. P. C. M. Krijn, Phys. Rev. Lett. 73, 2107 (1994)[2] C. Ferreyra, M. Rengifo, M.J. Sánchez, A. S. Everhardt, B. Noheda, and D. Rubi, Phys. Rev. Appl. 14, 044045 (2020)[3] M. J. Rozenberg, M. J. Sánchez, R. Weht, C. Acha, F. Gomez-Marlasca, and P. Levy, Phys. Rev. B 81, 115101 (2010).