Papers by Keyword: ReRAM

Abstract: Redox-based resistive switching devices (ReRAM) provide new hardware concepts which make it possible to break the von Neumann bottleneck and build a new computing system in the information. However, the materials for switching layers are various and mechanisms are quite different, these will block the further exploration for practical applications. This review tends to demonstrate different kinds of memristors fabricated with various materials, such as oxide, nitride and 2D materials. The electrical properties of those based on different materials are compared and the advantages of each are listed. It would give a guidance to the selection of materials of memristors.

Abstract: The properties and applications of materials with non-volatile memory based on HfO₂ were briefly considered. In addition, an overview of the obtained results was given. On the basis of these results, the possibility of use of the structures TiN/ Hf_0.5Zr_0.5O₂/ TiN/ SiO₂/ Si and TiN/ HfxAl_1-xO_y/ Pt/ SiO₂/ Si for the non-volatile memory of FeRAM and ReRAM types obtained by the atomic-layer deposition was shown. In addition, the scalability of these elements and opportunity to create promising submicron integrated circuits for ferroelectric and resistive memory were demonstrated.

Abstract: We study the structure of nonstoichiometric HfO_x films with variable composition using methods of XPS, spectroscopic ellipsometry, and ab initio calculations. According to XPS and optical absorption experiment data HfO_x consists of metal Hf and ~10-15% of nonstoichiometric hafnium sub-oxide HfO_y (y<2). HfO_y can be placed between HfO₂ and Hf, inside HfO₂, inside Hf. According to this model space fluctuations of chemical composition cause space fluctuations of bandgap in HfO_x. We found that transport in such electronic systems is described by percolation theory. This approach can be applied to explain LRS transport of HfO_x-based RRAM.

Abstract: Which parameter dominantly decides the value of time required to reset ReRAM (t_reset) among possible parameters, the value of a low resistance (R_L), voltage to induce reset (V_reset), and temperature to induce reset (T_reset) Although to answer this question is important to achieve faster resistive switching, detailed correlations between the parameters are still unclear. In this paper, we extracted t_reset, V_reset, R_L and T_reset at the same time by combining two electrical measurements. As a result, we found a clear correlation between V_reset, R_L, and T_reset, meaning that each parameter can not be controlled independently. T_reset increases not only with increasing V_reset but also with increasing R_L, which suggests the necessity of introducing ununiformly-shaped filamens and resistive switching takes place at the narrowing part of the filament.

Abstract: Resistive random access memory (ReRAM) is a promising candidate for next generation nonvolatile memory. La_0.7Sr_0.3.MnO₃ (LSMO) of perovskite manganite family has a great deal of attention for ReRAM material because it makes resistive switching (RS) of interface type without a “forming process”. However, the full understanding of the electronic structure and RS mechanism of LSMO remains a challenging problem. Therefore, this study performed spectromicroscopic analysis to understand the relation between the change of electronic structure and RS characteristic. The results demonstrated the electron occupation by field-induced oxygen vacancies and strong correlation effects.

Abstract: Multi-level-cell (MLC) operation of Cu-doped SiO_x-based (SiO_x:Cu-based) resistance random access memory (ReRAM) has been reported for the first time. For this study, we employed a novel ion bombardment-induced (IB-induced) SiO_x:Cu switching layer (SL). Using modulation of SET-current compliance, we completed 2-bit-per-cell memory application. The MLC resistance switching process is described in detail. Owing to controllability of Cu source from advanced IB technique, the IB-induced SiO_x:Cu SL shows good cell-to-cell uniformity of MLC resistance switching parameters, including operation voltages and resistance states. Additionally, the IB-induced TaN/SiO_x:Cu/TaN ReRAM exhibits infinite potential for MLC operation, such as over 3 times differentiation space among memory states, robust resistance retention, and promising operation endurance properties. During frequent MLC resistance switching, moreover, the IB-induced SiO_x:Cu-based device also has excellent single-cell uniformity of memory states due to IB-induced thin Cu filament.

Abstract: Both a low and a high resistance stateｓ which were written by the voltage application in a local region of NiO/Pt films by using conducting atomic force microscopy (C-AFM) were observed by using scanning electron microscope (SEM) and electron probe micro analysis (EPMA). The writing regions are distinguishable as dark areas in a secondary electron image and thus can be specified without using complicated sample fabrication process to narrow down the writing regions such as the photolithography technique. In addition, the writing regions were analyzed by using energy dispersive X-ray spectroscopy (EDS) mapping. No difference between the inside and outside of the writing regions is observed for all the mapped elements including C and Rh. Here, C and Rh are the most probable candidates for contamination which affect the secondary electron image. Therefore, our results suggested that the observed change in the contrast of the secondary electron image is related to the intrinsic change in the electronic state of the NiO film and a secondary electron yield is correlated to the physical properties of the film.

Abstract: Resistance random access memory (RRAM) is attractive as a next-generation form of nonvolatile memory. We investigated an electric field-induced resistance change of SrFeO2+x film as a candidate for RRAM material. SrFeO2.5-x film prepared at 300 oC showed hysteresis in its current-voltage curve and distinct pulse-switching properties. On the other hand, the sample prepared below 280 oC showed hysteresis in its current-voltage curve but didn’t show pulse-switching properties. The amount of oxygen in the sample and easiness of oxygen migration play important roles in the resistance-switching properties.

Abstract: Resistance-switching behaviors of the Pr0.7Ca0.3MnO3(PCMO) films based metalinsulator- metal (MIM) devices has been investigated. In this work, resistance change of PCMO films deposited with SRO buffer layers by using RF-magnetron sputtering system investigated at room temperature. The ratio of the resistance change of the PCMO films with SRO buffer layers in the high-resistance state to that in the low-resistance state turned out to be much lager than that of the PCMO films without SRO buffer layers. Moreover, The reproducible property of the fabricated samples were improved. Origin of resistance change is not clear, but PCMO films with SRO buffer layers have the possibility of application for nonvolatile memory device.