The stochastic nature of conductive filament formation and dissolution always leads to large fluctuations of key device parameters that hinder the practical applications of resistive random-access memories (RRAMs). Here, we report a simple bilayer oxide-based device structure of Al/TiO_x/TiO_y/FTO (x < y) employed to address this variability issue and improve the overall performance of the memory device. The bipolar resistive switching performance remarkably improved in these bilayer devices with lower forming voltage (~1 V), set/reset voltages of 0.4/-0.6 V, a programming current of 10 μA, an enlarged ON/OFF ratio (>10³), longer retention (>10³ s), and better uniformity as compared to the control Al/TiO_y/FTO device. Moreover, the modulation of TiO_x layer thickness enables tunability of switching voltages, currents, and the resistance window. In addition, reliable and reproducible multiple resistance states, more specifically different low resistance states, can be achieved in bilayer devices by controlling the programming current down to 10 μA, which is in contrast to the binary states of the control devices. These improved switching parameters with multilevel storage capability in bilayer devices are attributed to the incorporation of an oxygen vacancy-rich interfacial layer, namely TiO_x, which serves as an oxygen vacancy reservoir and facilitates effective conductive filament formation inside the switching layer. Furthermore, the thermodynamics involving the dielectric constant and Gibb's free energy of oxide formation at the Al/TiO_x and TiO_x/TiO_y interfaces play a pivotal role in the associated switching mechanism. The spatial variability of the operating voltage across these devices is found to be as low as 8%. These findings pave the way for low power, low cost, and high density data storage applications.

导电丝形成和溶解的随机性总是会导致关键器件参数的大幅波动，从而阻碍电阻式随机存取存储器 (RRAM) 的实际应用。在这里，我们报告了一种简单的基于双层氧化物的 Al/TiO _x /TiO _y /FTO (x < y)器件结构，用于解决这种可变性问题并提高存储器件的整体性能。这些双层器件的双极电阻开关性能显着提高，具有较低的形成电压 (~1 V)、0.4/-0.6 V 的设置/复位电压、10 μA 的编程电流、更大的 ON/OFF 比 (>10 ³ ) , 与对照 Al/TiO _y相比，保留时间更长 (>10 ³ s) 和更好的均匀性/FTO 设备。此外，TiO _x层厚度的调制能够实现开关电压、电流和电阻窗口的可调性。此外，通过将编程电流控制为低至 10 μA，可以在双层器件中实现可靠且可重复的多电阻状态，更具体地说是不同的低电阻状态，这与控制器件的二元状态相反。这些在双层器件中具有多级存储能力的改进开关参数归因于富氧空位界面层的结合，即 TiO _x，作为氧空位储存器，促进开关层内有效的导电细丝形成。此外，涉及介电常数和在 Al/TiO _x和 TiO _x /TiO _y界面处形成氧化物的吉布斯自由能的热力学在相关的转换机制中起关键作用。发现这些器件的工作电压的空间变异性低至 8%。这些发现为低功耗、低成本和高密度数据存储应用铺平了道路。