Low-power, bipolar resistive switching (RS) characteristics in the Ti/ZrO 2 /Pt nonvolatile memory with one transistor and one resistor (1T1R) architecture were reported. Multilevel storage behavior was observed by modulating the amplitude of the MOSFET gate voltage, in which the transistor functions as a current limiter. Furthermore, multilevel storage was also executed by controlling the reset voltage, leading the resistive random access memory (RRAM) to the multiple metastable low resistance state (LRS). The experimental results on the measured electrical properties of the various sized devices confirm that the RS mechanism of the Ti/ZrO 2 /Pt structure obeys the conducting filaments model. In application, the devices exhibit high-speed switching performances (250 ns) with suitable high/low resistance state ratio (HRS/LRS > 10). The LRS of the devices with 10 year retention ability at 80 • C, based on the Arrhenius equation, is also demonstrated in the thermal accelerating test. Furthermore, the ramping gate voltage method with fixed drain voltage is used to switch the 1T1R memory cells for upgrading the memory performances. Our experimental results suggest that the ZrO 2 -based RRAM is a prospective alternative for nonvolatile multilevel memory device applications.

The fabrication of SrZrO3 (SZO) memory devices with oxygen-rich (OR) and oxygen-deficient (OD) double layers, their resistive switching (RS) characteristics and mechanisms are investigated in this study. Due to the difference in oxygen content between the OR and OD layers formed by an oxygen flow control (OFC) process during SZO deposition, the RS region is effectively reduced and localized within the OR layer, which leads to a low operation voltage and stable RS behaviours. Furthermore, the OFC SZO device exhibits high-speed switching (10 ns) over 400 times and long retention (>106 s), showing promising potential for next-generation nonvolatile memory applications.

The preparation and electrical properties of Ti/Co Embedded (Co-E) ZrO2/Pt resistive switching memories are investigated. The Co nano-dots are formed in ZrO2 thin film after the memory device is annealed at 600 °C in N2 ambient for 60 s without any chemical reaction between Co and ZrO2, which is confirmed from the transmission electron microscopy, energy dispersive X-ray analyzer, and X-ray photoelectron spectroscopy observations. The devices exhibit low forming voltage of −1.5∼−2.8 V and robust negative bias unipolar resistive switching behaviors with small negative set voltage of −1.1∼−1.6 V. A physical model based on a filament mechanism is employed to explain the switching behaviors. It has a high potential for ultra high density nonvolatile memory applications.

Reproducible resistance switching characteristics of hafnium oxide-based nonvolatile memory devices

Nonpolar bistable resistive switching behaviors of sol-gel derived bismuth titanate oxide (BTO) thin film are investigated in this study. The BTO thin film memory device without thermal treatment shows higher resistance ratio (∼10 4 ) than the other annealed devices. The resistive switching behavior of the Pt/BTO/LNO/Pt device is reproducible and can be traced over 100 times. Both low resistance state (ON-state) and high resistance state (OFF-state) are stable over 10 4 s under 0.3 V voltage stress at room temperature (RT) and 85 • C. The retention behaviors of both memory states in the Pt/BTO/LNO/Pt device are very stable over 2 × 10 6 s at RT and 85 • C, showing that the BTO thin film memory device is a good candidate for nonvolatile memory application