Characteristics Of Memory Switching And Threshold Switching In Cu Conductive Filamentary Memristors

As an emerging basic information device,memristor has a wide application prospect in the fields of digital non-volatile high density memory,neuromorphic computing and reconfigurable logic operations,which has received explosive attention from both academic and industrial communities.By adjusting the stability of metallic conductive filament in memristors,non-volatile memory switching and volatile threshold switching can be realized.The former can be used as the physical basis of embedded memory and non-volatile logic operations,while the latter can be applied to selector,artificial neurons,random number generator and so on.In this paper,the characteristics and modulation of memory switching and threshold switching of Cu conductive filamentary memristors are systematically studied.High performance and non-volatile Cu/GeTe/TiN devices have been fabricated.The threshold switching characteristics have been successfully realized by using metal alloy Cu_xTe_1-x-x electrode and tantalum buffer layer.The common physical mechanism of these two kinds of switching characteristics is explored and the application prospects are discussed.The main results are summarized as follows:?1?In terms of memory switching:using semiconductor manufacturing technology such as film deposition,lithography and etching,the via hole Cu/GeTe/TiN memristors were fabricated,which exhibited high switching speed?<60 ns?,low operating voltage?<2 V?,low power consumption?<10 pJ?,high endurance?>10⁴ cycles?and good retention?>10⁴s@85 ⁰C?.Based on the analysis of current-voltage behaviors,area-independent properties and resistance-temperature characteristics,it is revealed that the charge carrier conduction mechanism in low resistance state is conductive filament and the electrons most probably hop via the Cu atoms or clusters.While the high resistive switching mechanism is Schottky emission.It is proposed that the existence of a Cu/Gap/Cu structure dominates the conduction of high resistance state,which indicates that a conical shape filament may grow from the counter TiN electrode surface.The non-volatile reconfigurable IMP/NOT and OR/COPY logic functions are realized experimentally by using anti-series structure of the Cu/GeTe/TiN memristors.The results indicate that the devices have potential application in low power storage-calculation integration technology.?2?In terms of threshold switching:two methods have been proposed to control the transport behavior of Cu ions in GeTe,thus controlling the threshold switching behavior of devices.Firstly,Cu_xTe_1-x metal alloy is used as the upper electrode to effectively control the content of injected Cu ions in the GeTe dielectric layer and the volatile threshold switching characteristics are successfully achieved in Cu_0.12Te/GeTe/TiN devices.Secondly,the influence of different Ta metal barrier layer thickness on the resistance switching behavior of Cu/Ta/GeTe/TiN devices is discussed.The experiment results show that Cu/Ta?4nm?/GeTe/TiN devices have stable threshold switching characteristics.But with the increase of compliance current,the number of Cu ions increases and the probability of filament spontaneous disrupt decreases.It leads to the increase of probability of non-volatile memory switching behavior.With the increase of Ta thickness?6nm?10nm?,memory switching characteristics occur in the device.It can be considered that Ta element directly participates in electrochemical reaction and resistance switching process.