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

C. FERREYRA; M .RENGIFO; M.J. SANCHEZ; A.S. EVERHARDT; B. NOHEDA; D. RUBI

Congreso; Materials Challenges for Memory; 2021

Memristors are metal/insulator/metal devices with high potential to be implemented as a new generation of non-volatile memories and novel new neuromorphic computing devices. These structures have the property of changing their resistance between different non-volatile states upon the application of external electrical stimuli, a process usually called resistive switching (RS). RS mechanisms are usually associated with the electromigration of defects such as oxygen vacancies (OV), either through the creation/disruption of conductive nanofilaments or by modulating the height of Schottky barriers, formed at metal/insulator interfaces. When the insulating oxide is ferroelectric, the resistive change at Schottky interfaces could be of electronic nature and associated to the switching of the direction of the ferroelectric polarization [1]. Ferroelectric memristors are considered to present a faster and more reliable response, as the physical mechanism does not require 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. Moreover, we propose that both effects are entangled and the latter is mainly controlled by the depolarizing field, arising from an incomplete screening of ferroelectric bound charges. We model 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).