Study On Design,preparation And Resistive Switching Properties Of ZnO Films Heterostructure

With the rapid development of storage technology,the semiconductor materials used in memories,especially the new generation of RRAM,continue to innovate.Resistance-switching memories are used in practical applications with broad prospects due to their low power consumption,high reading and writing efficiency,simple preparation and excellent fatigue resistance.ZnO film has the advantages of excellent electro-optical characteristics,easy growth and good crystallinity.It is widely used as the dielectric layer of resistive random access memory,and the single ZnO layer limits its performance improvement currently.In this paper,through the preparation of ZnO thin film and ZnO/STO structure resistive devices,the resistive characteristics of the devices are improved from the aspects of electrode interface effect,heterostructure composition,and transparent substrate.And the conduction mechanism is analyzed.The main research work of this paper is as follows:（1）The（002）oriented ZnO film was prepared on the Si substrate by magnetron sputtering,and the process parameters were improved.According to different coating atmospheres,（400）and（222）oriented ITO films were grown on silicon substrates.Based on different bottom electrodes,the influence of the thickness of the dielectric layer and the electrode structure on the structure and resistance performance of the ZnO thin film resistive switch was studied.The results show that the400nm thick ZnO film has the best crystallinity,and the ZnO film resistor fabricated on the（400）-ITO bottom electrode has the best electrical characteristics,and the switch window size is 2×10³.In order to improve the resistance switching characteristics,ITO and Pt top electrodes are used,and it is found that the Pt/ZnO/（222）-ITO structure has a larger switching ratio 10⁴.The Ⅰ-Ⅴ curve analysis shows that the resistance switching behavior of the ZnO thin film resistor can be explained by SCLC and oxygen vacancy conductive filament model.（2）The impact of the STO buffer layer on the resistance characteristics of the ZnO thin film heterostructure.STO buffer layers with different growth times were prepared on the bottom electrodes of ITO and Pt.Studies have shown that the durability of resistive transformers with STO film deposition time of 3 min exceeds 100 scan cycles and the switching window reaches 10⁶.The heterostructures were prepared periodically,and it was found that the resistive switching characteristics of the（ZnO-STO）structure with the period of 3 were the best,and the storage window size was 10⁷.In order to reduce the power consumption of the resistive converter,it is found through experiments that the device with the thickness of the ZnO layer reduced to 300nm can maintain the original switching window size and reduce the switching voltage.The conductive mechanism of the ZnO/STO heterostructure resistor converter is explained by the connection and rupture of oxygen vacancy conductive filaments and the space charge limiting current effect.（3）Pt/ZnO/ITO layers were prepared on transparent substrate（JGS1,glass slide）,that ITO electrodes were prepared under two different conditions.The crystal structure orientation of the dielectric films on the two substrates is different from that on the silicon substrate,and the optical transmittance can reach more than 70%.The ZnO heterostructures with transparent materials as the substrate exhibit stable resistance-to-switch characteristics and their switching ratio can reach 10³.It is found that the addition of the buffer layer makes the memory window of Pt/ZnO/STO/ITO（15%O₂）/JGS1 structure reach 8×10⁴,which has the best electrical performance.