Optimization of the multi-mem response of topotactic redox La1/2Sr1/2Mn1/2Co1/2O3−x

Abstract

Memristive systems emerge as strong candidates for the implementation of resistive random access memories and neuromorphic computing devices, as they can mimic the electrical analog behavior or biological synapses. In addition, complementary functionalities, such as memcapacitance, could significantly improve the performance of bio-inspired devices in key issues, such as energy consumption. However, the physics of mem systems is not fully understood so far, hampering their large-scale implementation in devices. Perovskites that undergo topotactic transitions and redox reactions show improved performance as mem systems, compared to standard perovskites. In this paper, we analyze different strategies to optimize the multi-mem behavior (memristive and memcapacitive) of topotactic redox La1/2Sr1/2Mn1/2Co1/2O3−x (LSMCO) films grown on Nb:SrTiO3. We explored devices with different crystallinities (from amorphous to epitaxial LSMCO), out-of-plane orientation [(001) and (110)], and stimulated either with voltage or current pulses. We found that an optimum memory response is found for epitaxial (110) LSMCO stimulated with current pulses. Under these conditions, the system efficiently exchanges oxygen with the environment minimizing, at the same time, self-heating effects that trigger nanostructural and chemical changes that could affect the device integrity and performance. Our work contributes to pave the way for the integration of multi-mem topotactic redox oxide-based interfaces in multiple device architectures, in order to exploit their memristive and memcapacitive properties for data storage or neuromorphic computation.

Tuning the conductance topology in solids

“…Let us finalize the discussion by assessing how the nonlinearity of the transport response due to the availability of local generation and/or trapping sites affects the frequency tuning of the conductance and its character. An impedance analysis is best suited for this purpose since it is a state of the art tool for characterizing the performance of transport devices under external oscillatory drives [24]. However, using impedance spectroscopy nontrivial behaviors, such as the appearance of effective negative capacitance and unexpected complex loops are very common.…”

Effect of memristor’s potentiation-depression curves peculiarities in the convergence of physical perceptrons

“…Upon electrical cycling, the redox reaction takes place, oxygen is exchanged between LSMCO and the ambient and this (reversibly) switches the depletion layer of the n-p diode, formed at the NSTO/LSMCO interface, by changing the amount of p carriers and thus the balance between n and p carriers at both sides of the junction. Oxidized LSMCO is linked to a thinner depletion layer and a low resistance state, while reduced LSMCO is related to a thicker depletion layer and a high resistance state [12,13]. The sketches displayed in figures 1(g)-(i) depict the mentioned mechanisms.…”

“…This change could be either non-volatile or volatile, and several synaptic/neuron functionalities with different complexity can be therefore electrically replicated [7,8]. Memristive effects have been found for an enormous variety of materials, including simple [9] and complex [10] oxides, ferroelectrics [11], topotactic redox perovskites [12,13], halides [14] or 2D materials such as graphene [15], among others. Memristive effects in oxide based compounds usually rely on the electromigration of charged defects, such as oxygen vacancies [6].…”

Oxygen vacancy dynamics in Pt/TiOx/TaOy/Pt memristors: exchange with the environment and internal electromigration

“…The VEOV model simulates the migration of OV, ubiquitous in transition metal oxides, due to an applied external electrical stimulus and has been extensively employed to unveil the memristive response of several oxide based devices, even ferroelectrics and topotactic manganites [22,[41][42][43][44][45]. The key ingredients of the model are (i) the dependence of the resistivity of an oxide on its local oxygen stoichiometry and (ii) the strong electric fields that develop close to the electrode(s)/ oxide interface(s) -usually forming Schottky barriers-and/or at the interface between different oxides composing the device.…”