Universal memory, which combines the high-speed performance of present-day static random access memory (SRAM) [1] with the non-volatility of Flash [1] must realize several goals such as low operating current, size scalability, and compatibility with mass production to become a feasible memory alternative. The best approach towards the goal of high density is to utilize stackable structures with a crossbar geometry, [2] and to achieve low-temperature fabrication [3] while still retaining a selective switch (transistor or diode) as the data storage element. Thus for high-density applications, crossbar structures are ideal, whereas for non-volatility, resistance-change materials show the best promise. In order to realize the fabrication of universal memory elements, it is imperative to develop a class of materials and structures that combine robust processibility, strong scalability, and rapid programming speed with non-volatility and low power consumption. In our work, we have focused on defining just the storage node portion of the devices, which utilize the resistance change within the film to store information via two different stable resistance states. Here, we have attempted to determine the properties of such structures and to study the mechanisms behind resistance RAM (RRAM) storage. Our Ti-doped (0.1 wt %) NiO samples deposited at room temperature show favorable node characteristics such as the lowest write current reported thus far for a unipolar switching resistance-change-based device (ca. 10 lA). In addition, the programming speed is comparable to the write time of SRAM (10 ns). By combining this node element with an appropriate select switch, such as a high-performance diode, a threshold device, or a two-terminal non-ohmic device, it becomes possible to fabricate high-density universal memory. Indeed, the fabrication of universal memory as the next generation of non-volatile memory is the logical goal for research in this field. In comparison to Flash and dynamic RAM (DRAM), which are the current industry standards, next generation memories must combine the non-volatility of Flash with the high-speed performance of SRAM.[1] Several emerging non-volatile memory architectures have been investigated in order to fabricate materials that fit these specifications. [1,[4][5][6] For example, phase-change RAM (PRAM) [7] utilizes resistance switching accompanied by full or partial phase changes in chalcogenide materials induced by electrical pulses as a method for storing information. Recently, much effort has been devoted to investigations of magnetic race-track memory, a new concept in magnetic non-volatile memory involving the storage of information in the domain walls of materials. [8,9] Also, RRAM [3,[10][11][12][13][14][15][16][17][18] has been studied as a possible candidate for new memory storage devices. RRAM is based on either transition metal oxides that exhibit unipolar switching properties [10][11][12] or perovskite materials displaying bipolar switching properties; [13][14][15] essentially, this is...
