Investigation on the Stabilizing Effect of Titanium in HfO2-Based Resistive Switching Devices With Tungsten Electrode

Resistive switching (RS) devices, also referred to as resistive random access memories (ReRAMs), rely on a working principle based on the change of electrical resistance following proper external electrical stimuli. Since the demonstration of the first resistive memory based on a binary transition metal oxide (TMO) enclosed in a metal–insulator–metal (MIM) structure, this class of devices has been considered a key player for simple and low-cost memories. However, successful large-scale integration with standard complementary metal–oxide–semiconductor (CMOS) technologies still needs systematic investigations. In this work, we examine the beneficial effect titanium has when employed as a buffer layer between CMOS-compatible materials like hafnium dioxide and tungsten. Hindering the tungsten oxidation, Ti provides RS stabilization and allows getting faster responses from the devices. Through an extensive comparative study, the effect of both thickness and composition of Ti-based buffer layers is investigated. The reported results show how titanium can be effectively employed to stabilize and tailor the RS behavior of the devices, and they may open the way to the definition of new design rules for ReRAM–CMOS integration. Moreover, the gradual switching and the response speed tunability observed employing titanium might also extend the domain of interest of these results to brain-inspired computing applications

SiOx-based resistive switching memory integrated in nanopillar structure fabricated by nanosphere lithography

textA highly compact, one diode-one resistor (1D-1R) SiOx-based resistive switching memory device with nano-pillar architecture has been achieved for the first time using nano-sphere lithography. The average nano-pillar height and diameter are 1.3 μm and 130 nm, respectively. Low-voltage electroforming using DC bias and AC pulse response in the 50ns regime demonstrate good potential for high-speed, low-energy nonvolatile memory. Nano-sphere deposition, oxygen-plasma isolation, and nano-pillar formation by deep-Si-etching are studied and optimized for the 1D-1R configurations. Excellent electrical performance, data retention and the potential for wafer-scale integration are promising for future non-volatile memory applications.Materials Science and Engineerin

Self-consistent physical modeling of SiOx-based RRAM structures

We apply a unique three-dimensional (3D) physics-based atomistic simulator to study silicon-rich (SiOx, x<;2) resistive switching nonvolatile memory (RRAM) devices. We couple self-consistently a simulation of ion and electron transport to the `atomistic' simulator GARAND and a self-heating model to explore the switching processes in these structures. The simulation model is more advanced than other available phenomenological models based on the resistor breaker network. The simulator is calibrated with experimental data, and reconstructs accurately the formation and rupture of the conductive filament in the 3D space. We demonstrate how the simulator is useful for exploring the little-known physics of these promising devices, and show that switching is an intrinsic property of the SiOx layer. In general, the simulation framework is useful for providing efficient designs, in terms of performance, variability and reliability, for memory devices and circuits. The simulator validity is not limited to SiOx-based devices, and can be used to study other promising RRAM systems based, e.g., on transition metal oxides

Studies of resistance switching effects in metal/YBa2Cu3O7-x interface junctions

Current-voltage characteristics of planar junctions formed by an epitaxial c-axis oriented YBa2Cu3O7-x thin film micro-bridge and Ag counter-electrode were measured in the temperature range from 4.2 K to 300 K. A hysteretic behavior related to switching of the junction resistance from a high-resistive to a low-resistive state and vice-versa was observed and analyzed in terms of the maximal current bias and temperature dependence. The same effects were observed on a sub-micrometer scale YBa2Cu3O7-x thin film - PtIr point contact junctions using Scanning Tunneling Microscope. These phenomena are discussed within a diffusion model, describing an oxygen vacancy drift in YBa2Cu3O7-x films in the nano-scale vicinity of the junction interface under applied electrical fields.Comment: To be published in Applied Surface Science