Research On Resistive Switching Characteristics And Charge Transfer Mechanism Of Memristors Based On ZnO Nanomaterials

Semiconductor integrated circuit technology has made great progress in resistive random access memory.With the size of semiconductor devices gradually approaching the physical limit,people have progressively realized that new electronic devices have broader application prospects.Memristors as a new type of memory,their resistance can be switched from the high state（HRS）to a low state（LRS）,due to their non-volatile performance,high density,low power consumption,fast write/erase speed,and operation of a series of advantages such as simple system,it has gained a lot of attention in the next generation of data-storage technology.The negative differential resistance（NDR）effect is a peculiar phenomenon in which the current of the device is in a certain voltage range and the current decreases with the increase of the voltage.Resistive switching behavior and negative differential effects are considered to be the candidates that can be used to exchange conventional flash memory applications in next-generation storage devices.This article studies memristors with negative differential resistance（NDR）behavior,which has the potential to develop multifunctional electronic devices.Among many binary metal oxides,Zn O,which can form rich and diverse nanostructures,has attracted wide attention from researchers.Zn O has many advantages such as easy synthesis,non-toxicity,high transparency,etc.,and is widely used in solar cells,thin-film transistors,and sensors.In recent years,the application of Zn O in RRAM memory has been explored.The nanometer scale is the key to achieving both memristive and negative differential resistance effects.This paper mainly uses zinc oxide（Zn O）nanomaterials as the main dielectric layer to construct the memristor for experimental research.Through the dimensional adjustment of nanomaterials（one-dimensional-two-dimensional）,the construction of a heterojunction and the selection of a two-dimensional spatial confinement structure are used to adjust the performance of the memristor.This paper can be divided into four parts:Firstly,a large-area Zn O nanorod array was prepared on a zinc foil substrate with a low-cost and low-temperature method.Zinc is oxidized in the formamide/water mixed solution.Based on this,a sandwich structure of Ag/Zn O nanorod arrays/Zn memristor was prepared.At room temperature,the device observes both resistance-switching memory behavior（HRS/LRS ratio～10）and negative differential effect（maximum slope～3.85）.Among them,because the Zn O nanorod arrays grown directly on the Zn substrate achieve better contact with the Zn substrate,a more obvious Schottky barrier can be formed in the Zn O/Zn interface.Secondly,the Zn O film was deposited on the titanium sheet by magnetron sputtering.By changing the sputtering time,self-colored Zn O layers with different thicknesses were obtained,and the color of the above-mentioned Zn O layer can be adjusted by covering the Mo S₂layer.In addition,the coexistence of resistance switching behavior and negative differential phenomenon in Mo S₂/Zn O heterojunction devices was also proved.Among them,the bright yellow Ag/Mo S₂（50 nm）/Zn O（100 nm）/Ti devices showed the most ideal performance and durability.Thirdly,a double-layer memristor with Ga₂O₃/Zn O heterojunction structure was synthesized by magnetron sputtering,and it showed good resistance switching behavior.The memristor of the Ag/Ga₂O₃/Zn O Nanofilm/Ti structure has unique resistance change behavior and a negative differential resistance effect.The analysis showed that the ohmic conduction mode and the SCLC conduction mode appeared,and proved that the oxygen vacancies beneficial to the formation of Ag conductive filaments exist in the dielectric layer.This work explores a new technology by designing a new electronic device that can switch between the ohmic transmission mode and the SCLC conduction mode by adding a Zn O layer,which is of great significance for the development of new electronic devices.Fourthly,zinc-aluminum layered double hydroxide Zn-Al（LDH）film is directly deposited on aluminum（Al）foil substrate through solution reaction.In addition,the Ag/Zn-Al（LDH）/Al structure memristor was prepared by depositing Ag as the top electrode.Due to the mutual stacking,layered structure,and interaction of Ag ions and anions inside the Zn-Al（LDH）layer,the device exhibits a variable resistance switch resistance（from 10⁴to 10²）.The memristive performance is explained by the formation and rupture of nano-scale Ag filaments in Zn-Al（LDH）vertical nanosheets.This work shows that Zn-Al（LDH）vertical nanosheets have great potential for flexible storage devices.Therefore,the device has broad application prospects in the preparation of resistance switch memory.These results show that Zn-Al（LDH）nanosheet materials can meet the dielectric layer standards of non-volatile memory devices,not only show excellent resistive behavior under low operating voltage and high stability but also help to further understand the Redistribution behavior of ions on the nanoscale.Finally,some of the above-mentioned devices have realized the coexistence of resistance switching（RS）and negative differential resistance（NDR）at room temperature.Analysis suggests that the switching behavior between the high-resistance state and the low-resistance state is generally caused by the formation and rupture of the silver conductive wire.This work has reference significance for the future development of nonvolatile memristors with reliable multi-function（RS and NDR）electronic devices.