Status and Prospects of ZnO-Based Resistive Switching Memory Devices

In the advancement of the semiconductor device technology, ZnO could be a prospective alternative than the other metal oxides for its versatility and huge applications in different aspects. In this review, a thorough overview on ZnO for the application of resistive switching memory (RRAM) devices has been conducted. Various efforts that have been made to investigate and modulate the switching characteristics of ZnO-based switching memory devices are discussed. The use of ZnO layer in different structure, the different types of filament formation, and the different types of switching including complementary switching are reported. By considering the huge interest of transparent devices, this review gives the concrete overview of the present status and prospects of transparent RRAM devices based on ZnO. ZnO-based RRAM can be used for flexible memory devices, which is also covered here. Another challenge in ZnO-based RRAM is that the realization of ultra-thin and low power devices. Nevertheless, ZnO not only offers decent memory properties but also has a unique potential to be used as multifunctional nonvolatile memory devices. The impact of electrode materials, metal doping, stack structures, transparency, and flexibility on resistive switching properties and switching parameters of ZnO-based resistive switching memory devices are briefly compared. This review also covers the different nanostructured-based emerging resistive switching memory devices for low power scalable devices. It may give a valuable insight on developing ZnO-based RRAM and also should encourage researchers to overcome the challenges

Giant ferroelectric resistance switching controlled by a modulatory terminal for low-power neuromorphic in-memory computing

Ferroelectrics have been demonstrated as excellent building blocks for high-performance non-volatile memories, including memristors, which play critical roles in the hardware implementation of artificial synapses and in-memory computing. Here, we report that the emerging van der Waals ferroelectric α-In2Se3 can be used to successfully implement heterosynaptic plasticity (a fundamental but rarely emulated synaptic form) using a planar-six-terminal memristor architecture. Through pulse programming at a modulatory terminal, the resistance (or current) switching between two floating electrodes shows a ratio of >103, which is two orders of magnitude larger than that in other reported multiterminal memristors. The polarization change of the ferroelectric α-In2Se3 channel is responsible for the resistance switching at various paired terminals. Considering the device variation, the image recognition accuracy of the simulated neural network, AlexNet, can reach 98%. Moreover, these heterosynaptic devices can naturally realize non-volatile Boolean logic without an additional circuit component. Our results suggest that van der Waals ferroelectrics hold great potential for applications in complex brain-inspired computing systems and logic-in-memory computers