Asymmetric Resistive Switching of Bilayer HfO_x/AlO_y and AlO_y/HfO_x Memristors: The Oxide Layer Characteristics and Performance Optimization for Digital Set and Analog Reset Switching

Abstract

Understanding the resistance switching behavior of oxide-based memristive devices is critical for evaluating their usefulness in nonvolatile memory and/or in artificial neural networks. Oxide memristors often employ bi- or multilayered metal oxide thin films for improved performance compared to devices with a single-metal-oxide active layer. However, a clear understanding of the mechanisms that lead to improved performance for specific combinations of oxide thin films is still missing. Herein, we fabricated two types of bilayered heterostructure devices, with HfO x /AlO y and AlO y /HfO x bilayer films sandwiched between Au electrodes. Electrical responses of these bilayer devices reveal a digital set and an analog reset transition process. Single-layer HfO x and AlO y devices are also examined as control samples to validate the switching mechanism. The role of bilayered heterostructures is investigated using both the experimental and simulated results. Our results suggest that synergistic switching performance can be achieved with a proper combination of these materials, optimized structures, and proper test conditions. These results open the avenue for designing more efficient double- or multilayered memristive devices for an analog response.

Internal Resistor Effect of Multilayer-Structured Synaptic Device for Low-Power Operation

“…Because a larger synaptic device array can process more data in parallel, the high-density integration of the synaptic device is necessary. For this purpose, in this research, a simple two-terminal (2T)-based metal–insulator–metal (MIM)-structured memristor which has been studied for memory application is utilized as the synaptic device [ 12 , 13 , 14 , 15 , 16 , 17 , 18 ].…”

“…Although the memristor-based synaptic device array can lead to faster parallel data processing using VMM, further research is required to minimize its power consumption. However, ReRAM has been studied for memory application [ 16 , 29 ], research on the device operation mechanism [ 29 , 30 , 31 ], and research on ReRAMs composed of materials that are not CMOS-compatible [ 32 , 33 ]. Thus, in this study, a memristor-based 2T synaptic device with a multilayer structure was proposed to reduce the operating power while maintaining high-density integration.…”

Hydrogen-triggered metal filament rupture in Cu-based resistance switches

“…In recent years, resistance switches have been considered to be one of the most promising candidates as the next generation memory cells and neuromorphic devices, mainly due to their low power consumption, high read/write speed, size scalability and other advantages [ 1–4 ]. Resistance switches are composed of sandwich structure (electrode/insulator/electrode), in particular, the devices with the amorphous metal oxides (such as TaO x [ 5 ], NbO x [ 6 ], HfO x [ 7 ], AlO x [ 8 ]) as the insulator layer show excellent performance. The resistive switching processes of such devices are mainly due to the diffusion of active ions (such as metal cations, oxygen anions or positive charged oxygen vacancies) in the insulator layer under the electric field and/or Joule heating effects, which results in the formation (low resistance state, SET) or rupture (high resistance state, RESET) of conductive filaments (CF) between two electrodes [ 8–10 ].…”

Nonvolatile bipolar resistive switching characteristics of aluminum oxide grown by thermal oxidation processes

“…The memory window of the optimal RRAM, where the thickness of the Al 2 O 3 RS layer is 30 nm, is ∼10, and endurance is 85 cycles. Basnet et al employed atomic layer deposition (ALD) to prepare a HfO x /AlO y bilayer [6]. The fabricated Au/HfO x /AlO y /Au RRAM exhibits a memory window of 100.…”