Ternary Logic with Stateful Neural Networks Using a Bilayered TaO_X‐Based Memristor Exhibiting Ternary States

Abstract

A memristive stateful neural network allowing complete Boolean in-memory computing attracts high interest in future electronics. Various Boolean logic gates and functions demonstrated so far confirm their practical potential as an emerging computing device. However, spatio-temporal efficiency of the stateful logic is still too limited to replace conventional computing technologies. This study proposes a ternary-state memristor device (simply a ternary memristor) for application to ternary stateful logic. The ternary-state implementable memristor device is developed with bilayered tantalum oxide by precisely controlling the oxygen content in each oxide layer. The device can operate 157 ternary logic gates in one operational clock, which allows an experimental demonstration of a functionally complete three-valued Łukasiewicz logic system. An optimized logic cascading strategy with possible ternary gates is ≈20% more efficient than conventional binary stateful logic, suggesting it can be beneficial for higher performance in-memory computing.

A review of memristor: material and structure design, device performance, applications and prospects

“…Binary oxides have a simple composition, high stability, low cost, simple preparation process, and are compatible with the traditional CMOS process. They include TiO x [ 46–50 ], SiO x [ 51–53 ], AlO x [ 54 ], NiO x [ 55 , 56 ], CuO x [ 57 , 58 ], ZnO x [ 59 , 60 ], HfO x [ 61 , 62 ], TaO x [ 63 , 64 ], WO x [ 65 , 66 ], ZrO x [ 67 , 68 ], SnO x [ 69 ] etc. In particular, HfO x and TaO x are the most promising binary oxides due to their sub-ns operation speed and ultimate endurance of more than 10 10 cycles [ 70 ].…”

Controllability of the Conductive Filament in Porous SiOx Memristors by Humidity-Mediated Silver Ion Migration

“…1,2 Generally, the properties of oxide-based memristors mainly depend on resistance switching between the two conductors from the high-resistance state (HRS) to the low-resistance state (LRS) under electrical control. 3,4 The switching effects in oxide-based memristors are attributable to the nanoscale conductive filaments (CF), which are formed/annihilated by controlling the thermal or external electric field generation. 5,6 The memristive switching mechanism relies on electrochemical effects and nanoionic processes involving dissolution of metal atoms from an electrochemically active electrode.…”

“…Oxide-based memristors have large potential in future neuromorphic devices due to their simple structure, fast switching speed, and compatibility with complementary metal oxide semiconductor processing. , Generally, the properties of oxide-based memristors mainly depend on resistance switching between the two conductors from the high-resistance state (HRS) to the low-resistance state (LRS) under electrical control. , The switching effects in oxide-based memristors are attributable to the nanoscale conductive filaments (CF), which are formed/annihilated by controlling the thermal or external electric field generation. , The memristive switching mechanism relies on electrochemical effects and nanoionic processes involving dissolution of metal atoms from an electrochemically active electrode. The resulting migration of metal ions in an insulating matrix forms a metallic conductive bridge that is responsible for the change of the device resistance .…”

Implementation of ternary stateful logic based on ternary memristor

“…Luo et al 10 programmed memristors to three different resistances by applying current pulses of different amplitudes to achieve types of ternary logic gates, such as OR, AND, COPY, and so on. Kim and his team fabricated a ternary memristor 11 , that has two positive threshold voltages (PTVs). If the ternary memristor's state is HRS, and the applied voltage exceeds the smaller PTV but doesn't exceed the larger PTV, its state changes from the HRS to the intermediate resistance state (IRS).…”

“…These two structures are similar and both consist of two parallel memristors and one resistor, with the former having two memristors in the same direction and the latter in opposite directions. The method 11 for implementing ternary stateful logic proposed by Kim et al used a structure similar to the IMPLY, consisting of multiple parallel ternary memristors in the same direction and a resistor. When implementing a ternary stateful logic with this structure, the resistors' resistances are not equal during each operation step.…”