Preparation And Properties Modulation Of Bidirectional Selectors

With the rapid development of information technology,limited by the Von-Neumann bottleneck and the physical scale limit of transistors,traditional digital computers are becoming less efficient compared to the growing demand for data processing.In particular,hardware-based brain-inspired computing systems,which can achieve high-efficiency parallel data processing in unstructured data problems,have gathered more and more attention recently.Given the fact that the most data-intensive part in the bio-inspired computing system,the vector-matrix multiplication,can be naturally accelerated in a crossbar array of memory,therefore,a large-scale memory crossbar array is fundamental for realizing a functional hardware-based bio-inspired computing system.However,the sneak current,which could radically affect the read operation of the array in a negative manner,would become nonnegligible with the scale of the crossbar array increasing,therefore,a selector series connected to the memory could effectively suppress the sneak current in the crossbar array,is of urgent needs.In this work,a high nonlinearity bidirectional selector is achieved with metal oxides and two-dimensional materials as research objects,and the effects of fabrication parameters and material selection on the performance of selectors based on tunneling barrier and threshold switching behaviors have been systematically studied.The main research contents are as follows:（1）For tunneling barrier selectors,two tunneling barrier mechanisms,crested barrier and variable oxide thickness devices,are systematically studied based on a variety of transition metal oxide materials.It is found that the crested barrier shows advantages in obtaining high nonlinearity selectors compared to the variable oxide thickness devices.And,10⁴ of nonlinearity and 10⁷of endurance have been achieved in the crested barrier selector based on the ZnO/Ta₂O₅/ZnO stack.It is found that the high nonlinearity of the crested barrier device results from the reduction of the effective barrier under the applied electric field through the investigation of electrical transport mechanisms.（2）For threshold switching selectors,a unidirectional threshold switching with off-state current low to 10-11 A is realized by controlling the threshold voltage of the device by plasma treatment,the highly insulated h-BN is selected as the functional layer of the device,taking advantage of the atomic-level flat interface of two-dimensional materials.On this basis,the threshold switching from unidirectional to bidirectional is achieved by introducing graphene electrodes.And,it is proposed that this bidirectional transition comes from the blocking and confinement of metal ions by the graphene.