Resistive Memory Effects In Heterostructures With YBa₂Cu₃O₇Electrodes

The continuous scaling of integrated circuits and the increment of demands on portable devices requires enhanced nonvolatile memory performance. Flash memories, the mainstream nonvolatile memories at present, are difficult to be further scaled due to intrinsic physical limitations. On this background, resistive random access memories (RRAM), based on bi-stable resistive switching phenomena, have recently attracted much attention due to their simple structure, high density of integration, low power consumption and compatibility with the CMOS process. RRAM have been considered a promising candidate for the next generation nonvolatile memories. However, there are still a number of issues that should be clarified, especially the mechanism of resistive switching.In this work, we have prepared resistive switching heterostructures using YBa2Cu3O7(YBCO) conductive oxides as active electrodes and SrTiO3(STO) and ZrO2as dielectrics. We have studied:(1) the optimization of the epitaxial deposition of STO/YBCO and ZrO2/YBCO heterostructures by pulsed laser deposition (PLD) and structural and morphology characterizations; and (2) the transport characterisctis and resistive switching mechanism of these heterostructures based on YBCO electrodes. Major conclusions include: 1. Substrate temperature and oxygen partial pressure are found to be the most important parameters in PLD deposition of STO/YBCO and ZrO2/YBCO heterostructures on (001) STO substrates. XRD and XPS analysis shows that both heterostructures deposited with optimized parameters are of good epitaxial quality. AFM and SEM analyses show smooth surface and abrupt interface.2. The STO/YBCO and ZrO2/YBCO heterostructures show reproducible bipolar resistive switching with long data retention. On/Off ratios of STO/YBCO and ZrO2/YBCO are30and20, read at0.5V.3. Poole-Frankel conduction is found to dominate the high resistance state, while Schottky emission is suggested for the low resistance one. Electric field driven migration and redistribution of oxygen vacancies around the STO/YBCO and ZrO2/YBCO interface switch the conduction between the interface controlled and the bulk controlled mechanism and lead to the observed resistive switching.