Interface barrier-induced conversion of resistive switching mechanism in Mn-doped BiFeO3 memristor

Different from conductive filament (CF)-type counterparts, interface-type devices exhibit continuously gradual conductance changes, making them the potential for artificial synapses. In this paper, Mn-doped BiFeO3 (BFMO) devices with SrRuO3 and TiN bottom electrodes demonstrate the clear CF rather than the interface barrier type resistance-switching feature due to the high Schottky barrier. Considering the measured electron affinity of 3.52 eV and work function of 4.22 eV in the as-synthesized BFMO film (a weak n-type semiconductor, marked as n(-)), we fabricated a hetero-junction device with the Nb-doped SrTiO3 (NSTO) bottom electrode (a strong n-type semiconductor, marked as n(+)) exhibiting analog switch characteristics. The n(-)-n(+) hetero-junction between BFMO and NSTO reverses the operation polarity and leads to a barrier transition-dominated conductive behavior in the BFMO-based memristor. The device shows a large ON/OFF ratio over 1200, favorable stability after 10(4) s, continual multi-value characteristics, symmetrical long-term potentiation and depression, and synaptic plasticity with about 80 ns time constant. The investigation of resistive switching features, band structure, and synapse performance in this work provides a reference for the application of BiFeO3 in the field of the memristor. Published under an exclusive license by AIP Publishing.

Automated summary

Interface-type devices, unlike conductive filament (CF)-type devices, demonstrate continuous conductance changes and have the potential to be used as artificial synapses. This paper investigates Mn-doped BiFeO3 (BFMO) devices with different bottom electrodes and reveals their diverse resistance-switching behaviors. By fabricating a hetero-junction device with a Nb-doped SrTiO3 (NSTO) bottom electrode, the polarity of operation is reversed, leading to barrier transition-dominated conductive behavior in the BFMO-based memristor. The device exhibits various desirable characteristics such as a high ON/OFF ratio, favorable stability, multi-value characteristics, and synaptic plasticity.