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We demonstrate a hybrid memory device with both memory and selector characteristics by using Al2O3 (memory) and TiO2 (selector) layers. The proposed device exhibits tunable threshold voltage characteristics based on the length of the residual conductive filament (CF) in the Al2O3 layer. To confirm the switching characteristics, the stability of the metallic CFs in each of the Al2O3 and TiO2 layers is investigated via electrical measurements. Our findings reveal that the CF in the TiO2 layer, which acts as a selector device, spontaneously ruptures. In contrast, a stable residual CF is observed in the Al2O3 layer, which acts as a memory device. Furthermore, we confirm that the tunable threshold voltage characteristics relate to the different tunneling gap distance from the residual CF in Al22O3. These results enable the hybrid memory device to achieve a high on–off ratio, high selectivity, and low leakage current without integrating an additional selector device, thereby enabling implementation of a high-density three-dimensional cross-point array. [ABSTRACT FROM AUTHOR]

In this letter, we demonstrate the conductive-bridging RAM (CBRAM) with excellent multi-level cell (MLC) and linear conductance characteristics for an artificial synaptic device of neuromorphic systems. Our findings show that inherent characteristics of CBRAM can achieve the linear conductance and MLC characteristics as a product of an integer unit of the conductance. However, uncontrolled metal-ion injection into the switching layer results in a significant degradation of device uniformity, leading to degradation in the classification accuracy. Thus, we introduce a multi-layer CBRAM configuration (Cu/HfO2/Ta/Cu2S/W) to control the ionic motion in electrolytes. As a result of device engineering, highly improved classification accuracy is achieved using CIFAR-10 data set. [ABSTRACT FROM PUBLISHER]

In this letter, we demonstrate a self-limited conductive-bridging random access memory (CBRAM) that removes the necessity for external current compliance in a one selector–one resistor (1S1R) architecture. The standard Ge2Sb2Te5 (GST) is used as a CBRAM switching layer. In addition, Te-rich GST is also considered. Their performance is then compared. Both samples exhibit self-limited on-current characteristics, and the on-currents of the standard GST and Te-rich GST are ~300 and \sim 20~\mu \textA , respectively. The observed self-limited characteristics are caused by the Te in the GST layer because in the presence of Te, Cu tends to form a more stable CuTe phase that restrict Cu filament growth. Furthermore, to confirm the feasibility of crossbar array applications, the 1S1R device is evaluated using a Ag/TiO2-based threshold selector device reported in our previous work. Hence, we confirm leakage current reduction, a uniform resistance distribution, and stable retention characteristics in the 1S1R configuration with no external current compliance. [ABSTRACT FROM AUTHOR]

A phase change material (PCM) is implemented in a memristive device as an emerging technology for the next generation of nanoelectronics. In article number 1800360, Junsuk Rho and co‐workers develop a programmable metallization memristor with a simple Ag/phase change material/Pt structure using an alloy compound of Ge, Sb, Te (GST). The performance of the memory device is improved by a facile nitrogen‐dopant method. Reliable and reproducible uniform switching characteristics are reported by the nitrogen‐doped GST device. [ABSTRACT FROM AUTHOR]

Highlights • The virgin resistance and forming voltage are decreased with increasing Zr composition in Zr x Te 1−x (0.5 ≦ x ≦ 0.7) and decreasing electrolyte thickness. • The temperature-dependent resistance of the formed CF in Te-based CBRAM shows semiconducting behavior and a gradual change of conductance lower than 1.0 G 0 in the erase step. • Activation energy for the out-diffusion of Te atoms does not contribute significantly to the excellent retention characteristics of Te-CBRAM. Abstract In this work, we explore the electrical properties and data retention of Te-based conductive-bridge random-access memory (CBRAM) of Zr x Te 1−x /Al 2 O 3 /Pt cells. The virgin resistance and forming voltage are decreased with increasing Zr composition (0.5 ≦ x ≦ 0.7) and decreasing electrolyte thickness. The resistance of the conductive filament (CF) formed in the Te-CBRAM shows semiconducting behavior that is decreased with increasing temperature, whereas a Cu-based CBRAM shows metallic behavior. Furthermore, the conductance change of Te-based CBRAM, during the filament dissolution step, occurs with lower conductance units than those of Cu/Ag-based CBRAM. The most differentiable characteristics of both devices are the data retention. Te-based CBRAM shows better data stability at high temperature (150 °C) than Cu-based device. Accelerated tests (250, 270, and 300 °C) were performed to understand the data retention of the Te-CBRAM, yielding excellent retention characteristics (10 years at 177 °C) despite its relatively low activation energy (E a , 1.07 eV) than Cu/Ag- based devices. We believe that the excellent retention properties of Te-based devices are more influenced by the wide effective CF size than by E a. [ABSTRACT FROM AUTHOR]